Importing MiniSat2 070721 into trunk

20 files changed, 3904 insertions, 0 deletions

diff --git a/src/prop/minisat/LICENSE b/src/prop/minisat/LICENSE
new file mode 100644
index 000000000..c87a32731
--- /dev/null
+++ b/src/prop/minisat/LICENSE
@@ -0,0 +1,20 @@
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/src/prop/minisat/README b/src/prop/minisat/README
new file mode 100644
index 000000000..e1b79329b
--- /dev/null
+++ b/src/prop/minisat/README
@@ -0,0 +1,19 @@
+Directory overview:
+==================
+
+mtl/            Mini Template Library
+core/           A core version of the solver
+simp/           An extended solver with simplification capabilities
+README
+LICENSE
+
+To build (release version: without assertions, statically linked, etc):
+======================================================================
+
+cd { core | simp }
+gmake rs
+
+Usage:
+======
+
+TODO
diff --git a/src/prop/minisat/core/Main.C b/src/prop/minisat/core/Main.C
new file mode 100644
index 000000000..acef32cd5
--- /dev/null
+++ b/src/prop/minisat/core/Main.C
@@ -0,0 +1,344 @@
+/******************************************************************************************[Main.C]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#include <ctime>
+#include <cstring>
+#include <stdint.h>
+#include <errno.h>
+
+#include <signal.h>
+#include <zlib.h>
+
+#include "Solver.h"
+
+/*************************************************************************************/
+#ifdef _MSC_VER
+#include <ctime>
+
+static inline double cpuTime(void) {
+    return (double)clock() / CLOCKS_PER_SEC; }
+#else
+
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <unistd.h>
+
+static inline double cpuTime(void) {
+    struct rusage ru;
+    getrusage(RUSAGE_SELF, &ru);
+    return (double)ru.ru_utime.tv_sec + (double)ru.ru_utime.tv_usec / 1000000; }
+#endif
+
+
+#if defined(__linux__)
+static inline int memReadStat(int field)
+{
+    char    name[256];
+    pid_t pid = getpid();
+    sprintf(name, "/proc/%d/statm", pid);
+    FILE*   in = fopen(name, "rb");
+    if (in == NULL) return 0;
+    int     value;
+    for (; field >= 0; field--)
+        fscanf(in, "%d", &value);
+    fclose(in);
+    return value;
+}
+static inline uint64_t memUsed() { return (uint64_t)memReadStat(0) * (uint64_t)getpagesize(); }
+
+
+#elif defined(__FreeBSD__)
+static inline uint64_t memUsed(void) {
+    struct rusage ru;
+    getrusage(RUSAGE_SELF, &ru);
+    return ru.ru_maxrss*1024; }
+
+
+#else
+static inline uint64_t memUsed() { return 0; }
+#endif
+
+#if defined(__linux__)
+#include <fpu_control.h>
+#endif
+
+//=================================================================================================
+// DIMACS Parser:
+
+#define CHUNK_LIMIT 1048576
+
+class StreamBuffer {
+    gzFile  in;
+    char    buf[CHUNK_LIMIT];
+    int     pos;
+    int     size;
+
+    void assureLookahead() {
+        if (pos >= size) {
+            pos  = 0;
+            size = gzread(in, buf, sizeof(buf)); } }
+
+public:
+    StreamBuffer(gzFile i) : in(i), pos(0), size(0) {
+        assureLookahead(); }
+
+    int  operator *  () { return (pos >= size) ? EOF : buf[pos]; }
+    void operator ++ () { pos++; assureLookahead(); }
+};
+
+//- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+template<class B>
+static void skipWhitespace(B& in) {
+    while ((*in >= 9 && *in <= 13) || *in == 32)
+        ++in; }
+
+template<class B>
+static void skipLine(B& in) {
+    for (;;){
+        if (*in == EOF || *in == '\0') return;
+        if (*in == '\n') { ++in; return; }
+        ++in; } }
+
+template<class B>
+static int parseInt(B& in) {
+    int     val = 0;
+    bool    neg = false;
+    skipWhitespace(in);
+    if      (*in == '-') neg = true, ++in;
+    else if (*in == '+') ++in;
+    if (*in < '0' || *in > '9') reportf("PARSE ERROR! Unexpected char: %c\n", *in), exit(3);
+    while (*in >= '0' && *in <= '9')
+        val = val*10 + (*in - '0'),
+        ++in;
+    return neg ? -val : val; }
+
+template<class B>
+static void readClause(B& in, Solver& S, vec<Lit>& lits) {
+    int     parsed_lit, var;
+    lits.clear();
+    for (;;){
+        parsed_lit = parseInt(in);
+        if (parsed_lit == 0) break;
+        var = abs(parsed_lit)-1;
+        while (var >= S.nVars()) S.newVar();
+        lits.push( (parsed_lit > 0) ? Lit(var) : ~Lit(var) );
+    }
+}
+
+template<class B>
+static bool match(B& in, char* str) {
+    for (; *str != 0; ++str, ++in)
+        if (*str != *in)
+            return false;
+    return true;
+}
+
+
+template<class B>
+static void parse_DIMACS_main(B& in, Solver& S) {
+    vec<Lit> lits;
+    for (;;){
+        skipWhitespace(in);
+        if (*in == EOF)
+            break;
+        else if (*in == 'p'){
+            if (match(in, "p cnf")){
+                int vars    = parseInt(in);
+                int clauses = parseInt(in);
+                reportf("|  Number of variables:  %-12d                                         |\n", vars);
+                reportf("|  Number of clauses:    %-12d                                         |\n", clauses);
+            }else{
+                reportf("PARSE ERROR! Unexpected char: %c\n", *in), exit(3);
+            }
+        } else if (*in == 'c' || *in == 'p')
+            skipLine(in);
+        else
+            readClause(in, S, lits),
+            S.addClause(lits);
+    }
+}
+
+// Inserts problem into solver.
+//
+static void parse_DIMACS(gzFile input_stream, Solver& S) {
+    StreamBuffer in(input_stream);
+    parse_DIMACS_main(in, S); }
+
+
+//=================================================================================================
+
+
+void printStats(Solver& solver)
+{
+    double   cpu_time = cpuTime();
+    uint64_t mem_used = memUsed();
+    reportf("restarts              : %lld\n", solver.starts);
+    reportf("conflicts             : %-12lld   (%.0f /sec)\n", solver.conflicts   , solver.conflicts   /cpu_time);
+    reportf("decisions             : %-12lld   (%4.2f %% random) (%.0f /sec)\n", solver.decisions, (float)solver.rnd_decisions*100 / (float)solver.decisions, solver.decisions   /cpu_time);
+    reportf("propagations          : %-12lld   (%.0f /sec)\n", solver.propagations, solver.propagations/cpu_time);
+    reportf("conflict literals     : %-12lld   (%4.2f %% deleted)\n", solver.tot_literals, (solver.max_literals - solver.tot_literals)*100 / (double)solver.max_literals);
+    if (mem_used != 0) reportf("Memory used           : %.2f MB\n", mem_used / 1048576.0);
+    reportf("CPU time              : %g s\n", cpu_time);
+}
+
+Solver* solver;
+static void SIGINT_handler(int signum) {
+    reportf("\n"); reportf("*** INTERRUPTED ***\n");
+    printStats(*solver);
+    reportf("\n"); reportf("*** INTERRUPTED ***\n");
+    exit(1); }
+
+
+//=================================================================================================
+// Main:
+
+void printUsage(char** argv)
+{
+    reportf("USAGE: %s [options] <input-file> <result-output-file>\n\n  where input may be either in plain or gzipped DIMACS.\n\n", argv[0]);
+    reportf("OPTIONS:\n\n");
+    reportf("  -polarity-mode = {true,false,rnd}\n");
+    reportf("  -decay         = <num> [ 0 - 1 ]\n");
+    reportf("  -rnd-freq      = <num> [ 0 - 1 ]\n");
+    reportf("  -verbosity     = {0,1,2}\n");
+    reportf("\n");
+}
+
+
+const char* hasPrefix(const char* str, const char* prefix)
+{
+    int len = strlen(prefix);
+    if (strncmp(str, prefix, len) == 0)
+        return str + len;
+    else
+        return NULL;
+}
+
+
+int main(int argc, char** argv)
+{
+    Solver      S;
+    S.verbosity = 1;
+
+
+    int         i, j;
+    const char* value;
+    for (i = j = 0; i < argc; i++){
+        if ((value = hasPrefix(argv[i], "-polarity-mode="))){
+            if (strcmp(value, "true") == 0)
+                S.polarity_mode = Solver::polarity_true;
+            else if (strcmp(value, "false") == 0)
+                S.polarity_mode = Solver::polarity_false;
+            else if (strcmp(value, "rnd") == 0)
+                S.polarity_mode = Solver::polarity_rnd;
+            else{
+                reportf("ERROR! unknown polarity-mode %s\n", value);
+                exit(0); }
+
+        }else if ((value = hasPrefix(argv[i], "-rnd-freq="))){
+            double rnd;
+            if (sscanf(value, "%lf", &rnd) <= 0 || rnd < 0 || rnd > 1){
+                reportf("ERROR! illegal rnd-freq constant %s\n", value);
+                exit(0); }
+            S.random_var_freq = rnd;
+
+        }else if ((value = hasPrefix(argv[i], "-decay="))){
+            double decay;
+            if (sscanf(value, "%lf", &decay) <= 0 || decay <= 0 || decay > 1){
+                reportf("ERROR! illegal decay constant %s\n", value);
+                exit(0); }
+            S.var_decay = 1 / decay;
+
+        }else if ((value = hasPrefix(argv[i], "-verbosity="))){
+            int verbosity = (int)strtol(value, NULL, 10);
+            if (verbosity == 0 && errno == EINVAL){
+                reportf("ERROR! illegal verbosity level %s\n", value);
+                exit(0); }
+            S.verbosity = verbosity;
+
+        }else if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "-help") == 0 || strcmp(argv[i], "--help") == 0){
+            printUsage(argv);
+            exit(0);
+
+        }else if (strncmp(argv[i], "-", 1) == 0){
+            reportf("ERROR! unknown flag %s\n", argv[i]);
+            exit(0);
+
+        }else
+            argv[j++] = argv[i];
+    }
+    argc = j;
+
+
+    reportf("This is MiniSat 2.0 beta\n");
+#if defined(__linux__)
+    fpu_control_t oldcw, newcw;
+    _FPU_GETCW(oldcw); newcw = (oldcw & ~_FPU_EXTENDED) | _FPU_DOUBLE; _FPU_SETCW(newcw);
+    reportf("WARNING: for repeatability, setting FPU to use double precision\n");
+#endif
+    double cpu_time = cpuTime();
+
+    solver = &S;
+    signal(SIGINT,SIGINT_handler);
+    signal(SIGHUP,SIGINT_handler);
+
+    if (argc == 1)
+        reportf("Reading from standard input... Use '-h' or '--help' for help.\n");
+
+    gzFile in = (argc == 1) ? gzdopen(0, "rb") : gzopen(argv[1], "rb");
+    if (in == NULL)
+        reportf("ERROR! Could not open file: %s\n", argc == 1 ? "<stdin>" : argv[1]), exit(1);
+
+    reportf("============================[ Problem Statistics ]=============================\n");
+    reportf("|                                                                             |\n");
+
+    parse_DIMACS(in, S);
+    gzclose(in);
+    FILE* res = (argc >= 3) ? fopen(argv[2], "wb") : NULL;
+
+    double parse_time = cpuTime() - cpu_time;
+    reportf("|  Parsing time:         %-12.2f s                                       |\n", parse_time);
+
+    if (!S.simplify()){
+        reportf("Solved by unit propagation\n");
+        if (res != NULL) fprintf(res, "UNSAT\n"), fclose(res);
+        printf("UNSATISFIABLE\n");
+        exit(20);
+    }
+
+    bool ret = S.solve();
+    printStats(S);
+    reportf("\n");
+    printf(ret ? "SATISFIABLE\n" : "UNSATISFIABLE\n");
+    if (res != NULL){
+        if (ret){
+            fprintf(res, "SAT\n");
+            for (int i = 0; i < S.nVars(); i++)
+                if (S.model[i] != l_Undef)
+                    fprintf(res, "%s%s%d", (i==0)?"":" ", (S.model[i]==l_True)?"":"-", i+1);
+            fprintf(res, " 0\n");
+        }else
+            fprintf(res, "UNSAT\n");
+        fclose(res);
+    }
+
+#ifdef NDEBUG
+    exit(ret ? 10 : 20);     // (faster than "return", which will invoke the destructor for 'Solver')
+#endif
+}
diff --git a/src/prop/minisat/core/Makefile b/src/prop/minisat/core/Makefile
new file mode 100644
index 000000000..42128c6d6
--- /dev/null
+++ b/src/prop/minisat/core/Makefile
@@ -0,0 +1,7 @@
+MTL       = ../mtl
+CHDRS     = $(wildcard *.h) $(wildcard $(MTL)/*.h)
+EXEC      = minisat
+CFLAGS    = -I$(MTL) -Wall -ffloat-store
+LFLAGS    = -lz
+
+include ../mtl/template.mk
diff --git a/src/prop/minisat/core/Solver.C b/src/prop/minisat/core/Solver.C
new file mode 100644
index 000000000..404f4da5e
--- /dev/null
+++ b/src/prop/minisat/core/Solver.C
@@ -0,0 +1,741 @@
+/****************************************************************************************[Solver.C]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#include "Solver.h"
+#include "Sort.h"
+#include <cmath>
+
+
+//=================================================================================================
+// Constructor/Destructor:
+
+
+Solver::Solver() :
+
+    // Parameters: (formerly in 'SearchParams')
+    var_decay(1 / 0.95), clause_decay(1 / 0.999), random_var_freq(0.02)
+  , restart_first(100), restart_inc(1.5), learntsize_factor((double)1/(double)3), learntsize_inc(1.1)
+
+    // More parameters:
+    //
+  , expensive_ccmin  (true)
+  , polarity_mode    (polarity_false)
+  , verbosity        (0)
+
+    // Statistics: (formerly in 'SolverStats')
+    //
+  , starts(0), decisions(0), rnd_decisions(0), propagations(0), conflicts(0)
+  , clauses_literals(0), learnts_literals(0), max_literals(0), tot_literals(0)
+
+  , ok               (true)
+  , cla_inc          (1)
+  , var_inc          (1)
+  , qhead            (0)
+  , simpDB_assigns   (-1)
+  , simpDB_props     (0)
+  , order_heap       (VarOrderLt(activity))
+  , random_seed      (91648253)
+  , progress_estimate(0)
+  , remove_satisfied (true)
+{}
+
+
+Solver::~Solver()
+{
+    for (int i = 0; i < learnts.size(); i++) free(learnts[i]);
+    for (int i = 0; i < clauses.size(); i++) free(clauses[i]);
+}
+
+
+//=================================================================================================
+// Minor methods:
+
+
+// Creates a new SAT variable in the solver. If 'decision_var' is cleared, variable will not be
+// used as a decision variable (NOTE! This has effects on the meaning of a SATISFIABLE result).
+//
+Var Solver::newVar(bool sign, bool dvar)
+{
+    int v = nVars();
+    watches   .push();          // (list for positive literal)
+    watches   .push();          // (list for negative literal)
+    reason    .push(NULL);
+    assigns   .push(toInt(l_Undef));
+    level     .push(-1);
+    activity  .push(0);
+    seen      .push(0);
+
+    polarity    .push((char)sign);
+    decision_var.push((char)dvar);
+
+    insertVarOrder(v);
+    return v;
+}
+
+
+bool Solver::addClause(vec<Lit>& ps)
+{
+    assert(decisionLevel() == 0);
+
+    if (!ok)
+        return false;
+    else{
+        // Check if clause is satisfied and remove false/duplicate literals:
+        sort(ps);
+        Lit p; int i, j;
+        for (i = j = 0, p = lit_Undef; i < ps.size(); i++)
+            if (value(ps[i]) == l_True || ps[i] == ~p)
+                return true;
+            else if (value(ps[i]) != l_False && ps[i] != p)
+                ps[j++] = p = ps[i];
+        ps.shrink(i - j);
+    }
+
+    if (ps.size() == 0)
+        return ok = false;
+    else if (ps.size() == 1){
+        assert(value(ps[0]) == l_Undef);
+        uncheckedEnqueue(ps[0]);
+        return ok = (propagate() == NULL);
+    }else{
+        Clause* c = Clause_new(ps, false);
+        clauses.push(c);
+        attachClause(*c);
+    }
+
+    return true;
+}
+
+
+void Solver::attachClause(Clause& c) {
+    assert(c.size() > 1);
+    watches[toInt(~c[0])].push(&c);
+    watches[toInt(~c[1])].push(&c);
+    if (c.learnt()) learnts_literals += c.size();
+    else            clauses_literals += c.size(); }
+
+
+void Solver::detachClause(Clause& c) {
+    assert(c.size() > 1);
+    assert(find(watches[toInt(~c[0])], &c));
+    assert(find(watches[toInt(~c[1])], &c));
+    remove(watches[toInt(~c[0])], &c);
+    remove(watches[toInt(~c[1])], &c);
+    if (c.learnt()) learnts_literals -= c.size();
+    else            clauses_literals -= c.size(); }
+
+
+void Solver::removeClause(Clause& c) {
+    detachClause(c);
+    free(&c); }
+
+
+bool Solver::satisfied(const Clause& c) const {
+    for (int i = 0; i < c.size(); i++)
+        if (value(c[i]) == l_True)
+            return true;
+    return false; }
+
+
+// Revert to the state at given level (keeping all assignment at 'level' but not beyond).
+//
+void Solver::cancelUntil(int level) {
+    if (decisionLevel() > level){
+        for (int c = trail.size()-1; c >= trail_lim[level]; c--){
+            Var     x  = var(trail[c]);
+            assigns[x] = toInt(l_Undef);
+            insertVarOrder(x); }
+        qhead = trail_lim[level];
+        trail.shrink(trail.size() - trail_lim[level]);
+        trail_lim.shrink(trail_lim.size() - level);
+    } }
+
+
+//=================================================================================================
+// Major methods:
+
+
+Lit Solver::pickBranchLit(int polarity_mode, double random_var_freq)
+{
+    Var next = var_Undef;
+
+    // Random decision:
+    if (drand(random_seed) < random_var_freq && !order_heap.empty()){
+        next = order_heap[irand(random_seed,order_heap.size())];
+        if (toLbool(assigns[next]) == l_Undef && decision_var[next])
+            rnd_decisions++; }
+
+    // Activity based decision:
+    while (next == var_Undef || toLbool(assigns[next]) != l_Undef || !decision_var[next])
+        if (order_heap.empty()){
+            next = var_Undef;
+            break;
+        }else
+            next = order_heap.removeMin();
+
+    bool sign = false;
+    switch (polarity_mode){
+    case polarity_true:  sign = false; break;
+    case polarity_false: sign = true;  break;
+    case polarity_user:  sign = polarity[next]; break;
+    case polarity_rnd:   sign = irand(random_seed, 2); break;
+    default: assert(false); }
+
+    return next == var_Undef ? lit_Undef : Lit(next, sign);
+}
+
+
+/*_________________________________________________________________________________________________
+|
+|  analyze : (confl : Clause*) (out_learnt : vec<Lit>&) (out_btlevel : int&)  ->  [void]
+|  
+|  Description:
+|    Analyze conflict and produce a reason clause.
+|  
+|    Pre-conditions:
+|      * 'out_learnt' is assumed to be cleared.
+|      * Current decision level must be greater than root level.
+|  
+|    Post-conditions:
+|      * 'out_learnt[0]' is the asserting literal at level 'out_btlevel'.
+|  
+|  Effect:
+|    Will undo part of the trail, upto but not beyond the assumption of the current decision level.
+|________________________________________________________________________________________________@*/
+void Solver::analyze(Clause* confl, vec<Lit>& out_learnt, int& out_btlevel)
+{
+    int pathC = 0;
+    Lit p     = lit_Undef;
+
+    // Generate conflict clause:
+    //
+    out_learnt.push();      // (leave room for the asserting literal)
+    int index   = trail.size() - 1;
+    out_btlevel = 0;
+
+    do{
+        assert(confl != NULL);          // (otherwise should be UIP)
+        Clause& c = *confl;
+
+        if (c.learnt())
+            claBumpActivity(c);
+
+        for (int j = (p == lit_Undef) ? 0 : 1; j < c.size(); j++){
+            Lit q = c[j];
+
+            if (!seen[var(q)] && level[var(q)] > 0){
+                varBumpActivity(var(q));
+                seen[var(q)] = 1;
+                if (level[var(q)] >= decisionLevel())
+                    pathC++;
+                else{
+                    out_learnt.push(q);
+                    if (level[var(q)] > out_btlevel)
+                        out_btlevel = level[var(q)];
+                }
+            }
+        }
+
+        // Select next clause to look at:
+        while (!seen[var(trail[index--])]);
+        p     = trail[index+1];
+        confl = reason[var(p)];
+        seen[var(p)] = 0;
+        pathC--;
+
+    }while (pathC > 0);
+    out_learnt[0] = ~p;
+
+    // Simplify conflict clause:
+    //
+    int i, j;
+    if (expensive_ccmin){
+        uint32_t abstract_level = 0;
+        for (i = 1; i < out_learnt.size(); i++)
+            abstract_level |= abstractLevel(var(out_learnt[i])); // (maintain an abstraction of levels involved in conflict)
+
+        out_learnt.copyTo(analyze_toclear);
+        for (i = j = 1; i < out_learnt.size(); i++)
+            if (reason[var(out_learnt[i])] == NULL || !litRedundant(out_learnt[i], abstract_level))
+                out_learnt[j++] = out_learnt[i];
+    }else{
+        out_learnt.copyTo(analyze_toclear);
+        for (i = j = 1; i < out_learnt.size(); i++){
+            Clause& c = *reason[var(out_learnt[i])];
+            for (int k = 1; k < c.size(); k++)
+                if (!seen[var(c[k])] && level[var(c[k])] > 0){
+                    out_learnt[j++] = out_learnt[i];
+                    break; }
+        }
+    }
+    max_literals += out_learnt.size();
+    out_learnt.shrink(i - j);
+    tot_literals += out_learnt.size();
+
+    // Find correct backtrack level:
+    //
+    if (out_learnt.size() == 1)
+        out_btlevel = 0;
+    else{
+        int max_i = 1;
+        for (int i = 2; i < out_learnt.size(); i++)
+            if (level[var(out_learnt[i])] > level[var(out_learnt[max_i])])
+                max_i = i;
+        Lit p             = out_learnt[max_i];
+        out_learnt[max_i] = out_learnt[1];
+        out_learnt[1]     = p;
+        out_btlevel       = level[var(p)];
+    }
+
+
+    for (int j = 0; j < analyze_toclear.size(); j++) seen[var(analyze_toclear[j])] = 0;    // ('seen[]' is now cleared)
+}
+
+
+// Check if 'p' can be removed. 'abstract_levels' is used to abort early if the algorithm is
+// visiting literals at levels that cannot be removed later.
+bool Solver::litRedundant(Lit p, uint32_t abstract_levels)
+{
+    analyze_stack.clear(); analyze_stack.push(p);
+    int top = analyze_toclear.size();
+    while (analyze_stack.size() > 0){
+        assert(reason[var(analyze_stack.last())] != NULL);
+        Clause& c = *reason[var(analyze_stack.last())]; analyze_stack.pop();
+
+        for (int i = 1; i < c.size(); i++){
+            Lit p  = c[i];
+            if (!seen[var(p)] && level[var(p)] > 0){
+                if (reason[var(p)] != NULL && (abstractLevel(var(p)) & abstract_levels) != 0){
+                    seen[var(p)] = 1;
+                    analyze_stack.push(p);
+                    analyze_toclear.push(p);
+                }else{
+                    for (int j = top; j < analyze_toclear.size(); j++)
+                        seen[var(analyze_toclear[j])] = 0;
+                    analyze_toclear.shrink(analyze_toclear.size() - top);
+                    return false;
+                }
+            }
+        }
+    }
+
+    return true;
+}
+
+
+/*_________________________________________________________________________________________________
+|
+|  analyzeFinal : (p : Lit)  ->  [void]
+|  
+|  Description:
+|    Specialized analysis procedure to express the final conflict in terms of assumptions.
+|    Calculates the (possibly empty) set of assumptions that led to the assignment of 'p', and
+|    stores the result in 'out_conflict'.
+|________________________________________________________________________________________________@*/
+void Solver::analyzeFinal(Lit p, vec<Lit>& out_conflict)
+{
+    out_conflict.clear();
+    out_conflict.push(p);
+
+    if (decisionLevel() == 0)
+        return;
+
+    seen[var(p)] = 1;
+
+    for (int i = trail.size()-1; i >= trail_lim[0]; i--){
+        Var x = var(trail[i]);
+        if (seen[x]){
+            if (reason[x] == NULL){
+                assert(level[x] > 0);
+                out_conflict.push(~trail[i]);
+            }else{
+                Clause& c = *reason[x];
+                for (int j = 1; j < c.size(); j++)
+                    if (level[var(c[j])] > 0)
+                        seen[var(c[j])] = 1;
+            }
+            seen[x] = 0;
+        }
+    }
+
+    seen[var(p)] = 0;
+}
+
+
+void Solver::uncheckedEnqueue(Lit p, Clause* from)
+{
+    assert(value(p) == l_Undef);
+    assigns [var(p)] = toInt(lbool(!sign(p)));  // <<== abstract but not uttermost effecient
+    level   [var(p)] = decisionLevel();
+    reason  [var(p)] = from;
+    trail.push(p);
+}
+
+
+/*_________________________________________________________________________________________________
+|
+|  propagate : [void]  ->  [Clause*]
+|  
+|  Description:
+|    Propagates all enqueued facts. If a conflict arises, the conflicting clause is returned,
+|    otherwise NULL.
+|  
+|    Post-conditions:
+|      * the propagation queue is empty, even if there was a conflict.
+|________________________________________________________________________________________________@*/
+Clause* Solver::propagate()
+{
+    Clause* confl     = NULL;
+    int     num_props = 0;
+
+    while (qhead < trail.size()){
+        Lit            p   = trail[qhead++];     // 'p' is enqueued fact to propagate.
+        vec<Clause*>&  ws  = watches[toInt(p)];
+        Clause         **i, **j, **end;
+        num_props++;
+
+        for (i = j = (Clause**)ws, end = i + ws.size();  i != end;){
+            Clause& c = **i++;
+
+            // Make sure the false literal is data[1]:
+            Lit false_lit = ~p;
+            if (c[0] == false_lit)
+                c[0] = c[1], c[1] = false_lit;
+
+            assert(c[1] == false_lit);
+
+            // If 0th watch is true, then clause is already satisfied.
+            Lit first = c[0];
+            if (value(first) == l_True){
+                *j++ = &c;
+            }else{
+                // Look for new watch:
+                for (int k = 2; k < c.size(); k++)
+                    if (value(c[k]) != l_False){
+                        c[1] = c[k]; c[k] = false_lit;
+                        watches[toInt(~c[1])].push(&c);
+                        goto FoundWatch; }
+
+                // Did not find watch -- clause is unit under assignment:
+                *j++ = &c;
+                if (value(first) == l_False){
+                    confl = &c;
+                    qhead = trail.size();
+                    // Copy the remaining watches:
+                    while (i < end)
+                        *j++ = *i++;
+                }else
+                    uncheckedEnqueue(first, &c);
+            }
+        FoundWatch:;
+        }
+        ws.shrink(i - j);
+    }
+    propagations += num_props;
+    simpDB_props -= num_props;
+
+    return confl;
+}
+
+/*_________________________________________________________________________________________________
+|
+|  reduceDB : ()  ->  [void]
+|  
+|  Description:
+|    Remove half of the learnt clauses, minus the clauses locked by the current assignment. Locked
+|    clauses are clauses that are reason to some assignment. Binary clauses are never removed.
+|________________________________________________________________________________________________@*/
+struct reduceDB_lt { bool operator () (Clause* x, Clause* y) { return x->size() > 2 && (y->size() == 2 || x->activity() < y->activity()); } };
+void Solver::reduceDB()
+{
+    int     i, j;
+    double  extra_lim = cla_inc / learnts.size();    // Remove any clause below this activity
+
+    sort(learnts, reduceDB_lt());
+    for (i = j = 0; i < learnts.size() / 2; i++){
+        if (learnts[i]->size() > 2 && !locked(*learnts[i]))
+            removeClause(*learnts[i]);
+        else
+            learnts[j++] = learnts[i];
+    }
+    for (; i < learnts.size(); i++){
+        if (learnts[i]->size() > 2 && !locked(*learnts[i]) && learnts[i]->activity() < extra_lim)
+            removeClause(*learnts[i]);
+        else
+            learnts[j++] = learnts[i];
+    }
+    learnts.shrink(i - j);
+}
+
+
+void Solver::removeSatisfied(vec<Clause*>& cs)
+{
+    int i,j;
+    for (i = j = 0; i < cs.size(); i++){
+        if (satisfied(*cs[i]))
+            removeClause(*cs[i]);
+        else
+            cs[j++] = cs[i];
+    }
+    cs.shrink(i - j);
+}
+
+
+/*_________________________________________________________________________________________________
+|
+|  simplify : [void]  ->  [bool]
+|  
+|  Description:
+|    Simplify the clause database according to the current top-level assigment. Currently, the only
+|    thing done here is the removal of satisfied clauses, but more things can be put here.
+|________________________________________________________________________________________________@*/
+bool Solver::simplify()
+{
+    assert(decisionLevel() == 0);
+
+    if (!ok || propagate() != NULL)
+        return ok = false;
+
+    if (nAssigns() == simpDB_assigns || (simpDB_props > 0))
+        return true;
+
+    // Remove satisfied clauses:
+    removeSatisfied(learnts);
+    if (remove_satisfied)        // Can be turned off.
+        removeSatisfied(clauses);
+
+    // Remove fixed variables from the variable heap:
+    order_heap.filter(VarFilter(*this));
+
+    simpDB_assigns = nAssigns();
+    simpDB_props   = clauses_literals + learnts_literals;   // (shouldn't depend on stats really, but it will do for now)
+
+    return true;
+}
+
+
+/*_________________________________________________________________________________________________
+|
+|  search : (nof_conflicts : int) (nof_learnts : int) (params : const SearchParams&)  ->  [lbool]
+|  
+|  Description:
+|    Search for a model the specified number of conflicts, keeping the number of learnt clauses
+|    below the provided limit. NOTE! Use negative value for 'nof_conflicts' or 'nof_learnts' to
+|    indicate infinity.
+|  
+|  Output:
+|    'l_True' if a partial assigment that is consistent with respect to the clauseset is found. If
+|    all variables are decision variables, this means that the clause set is satisfiable. 'l_False'
+|    if the clause set is unsatisfiable. 'l_Undef' if the bound on number of conflicts is reached.
+|________________________________________________________________________________________________@*/
+lbool Solver::search(int nof_conflicts, int nof_learnts)
+{
+    assert(ok);
+    int         backtrack_level;
+    int         conflictC = 0;
+    vec<Lit>    learnt_clause;
+
+    starts++;
+
+    bool first = true;
+
+    for (;;){
+        Clause* confl = propagate();
+        if (confl != NULL){
+            // CONFLICT
+            conflicts++; conflictC++;
+            if (decisionLevel() == 0) return l_False;
+
+            first = false;
+
+            learnt_clause.clear();
+            analyze(confl, learnt_clause, backtrack_level);
+            cancelUntil(backtrack_level);
+            assert(value(learnt_clause[0]) == l_Undef);
+
+            if (learnt_clause.size() == 1){
+                uncheckedEnqueue(learnt_clause[0]);
+            }else{
+                Clause* c = Clause_new(learnt_clause, true);
+                learnts.push(c);
+                attachClause(*c);
+                claBumpActivity(*c);
+                uncheckedEnqueue(learnt_clause[0], c);
+            }
+
+            varDecayActivity();
+            claDecayActivity();
+
+        }else{
+            // NO CONFLICT
+
+            if (nof_conflicts >= 0 && conflictC >= nof_conflicts){
+                // Reached bound on number of conflicts:
+                progress_estimate = progressEstimate();
+                cancelUntil(0);
+                return l_Undef; }
+
+            // Simplify the set of problem clauses:
+            if (decisionLevel() == 0 && !simplify())
+                return l_False;
+
+            if (nof_learnts >= 0 && learnts.size()-nAssigns() >= nof_learnts)
+                // Reduce the set of learnt clauses:
+                reduceDB();
+
+            Lit next = lit_Undef;
+            while (decisionLevel() < assumptions.size()){
+                // Perform user provided assumption:
+                Lit p = assumptions[decisionLevel()];
+                if (value(p) == l_True){
+                    // Dummy decision level:
+                    newDecisionLevel();
+                }else if (value(p) == l_False){
+                    analyzeFinal(~p, conflict);
+                    return l_False;
+                }else{
+                    next = p;
+                    break;
+                }
+            }
+
+            if (next == lit_Undef){
+                // New variable decision:
+                decisions++;
+                next = pickBranchLit(polarity_mode, random_var_freq);
+
+                if (next == lit_Undef)
+                    // Model found:
+                    return l_True;
+            }
+
+            // Increase decision level and enqueue 'next'
+            assert(value(next) == l_Undef);
+            newDecisionLevel();
+            uncheckedEnqueue(next);
+        }
+    }
+}
+
+
+double Solver::progressEstimate() const
+{
+    double  progress = 0;
+    double  F = 1.0 / nVars();
+
+    for (int i = 0; i <= decisionLevel(); i++){
+        int beg = i == 0 ? 0 : trail_lim[i - 1];
+        int end = i == decisionLevel() ? trail.size() : trail_lim[i];
+        progress += pow(F, i) * (end - beg);
+    }
+
+    return progress / nVars();
+}
+
+
+bool Solver::solve(const vec<Lit>& assumps)
+{
+    model.clear();
+    conflict.clear();
+
+    if (!ok) return false;
+
+    assumps.copyTo(assumptions);
+
+    double  nof_conflicts = restart_first;
+    double  nof_learnts   = nClauses() * learntsize_factor;
+    lbool   status        = l_Undef;
+
+    if (verbosity >= 1){
+        reportf("============================[ Search Statistics ]==============================\n");
+        reportf("| Conflicts |          ORIGINAL         |          LEARNT          | Progress |\n");
+        reportf("|           |    Vars  Clauses Literals |    Limit  Clauses Lit/Cl |          |\n");
+        reportf("===============================================================================\n");
+    }
+
+    // Search:
+    while (status == l_Undef){
+        if (verbosity >= 1)
+            reportf("| %9d | %7d %8d %8d | %8d %8d %6.0f | %6.3f %% |\n", (int)conflicts, order_heap.size(), nClauses(), (int)clauses_literals, (int)nof_learnts, nLearnts(), (double)learnts_literals/nLearnts(), progress_estimate*100), fflush(stdout);
+        status = search((int)nof_conflicts, (int)nof_learnts);
+        nof_conflicts *= restart_inc;
+        nof_learnts   *= learntsize_inc;
+    }
+
+    if (verbosity >= 1)
+        reportf("===============================================================================\n");
+
+
+    if (status == l_True){
+        // Extend & copy model:
+        model.growTo(nVars());
+        for (int i = 0; i < nVars(); i++) model[i] = value(i);
+#ifndef NDEBUG
+        verifyModel();
+#endif
+    }else{
+        assert(status == l_False);
+        if (conflict.size() == 0)
+            ok = false;
+    }
+
+    cancelUntil(0);
+    return status == l_True;
+}
+
+//=================================================================================================
+// Debug methods:
+
+
+void Solver::verifyModel()
+{
+    bool failed = false;
+    for (int i = 0; i < clauses.size(); i++){
+        assert(clauses[i]->mark() == 0);
+        Clause& c = *clauses[i];
+        for (int j = 0; j < c.size(); j++)
+            if (modelValue(c[j]) == l_True)
+                goto next;
+
+        reportf("unsatisfied clause: ");
+        printClause(*clauses[i]);
+        reportf("\n");
+        failed = true;
+    next:;
+    }
+
+    assert(!failed);
+
+    reportf("Verified %d original clauses.\n", clauses.size());
+}
+
+
+void Solver::checkLiteralCount()
+{
+    // Check that sizes are calculated correctly:
+    int cnt = 0;
+    for (int i = 0; i < clauses.size(); i++)
+        if (clauses[i]->mark() == 0)
+            cnt += clauses[i]->size();
+
+    if ((int)clauses_literals != cnt){
+        fprintf(stderr, "literal count: %d, real value = %d\n", (int)clauses_literals, cnt);
+        assert((int)clauses_literals == cnt);
+    }
+}
diff --git a/src/prop/minisat/core/Solver.h b/src/prop/minisat/core/Solver.h
new file mode 100644
index 000000000..0137b6ff3
--- /dev/null
+++ b/src/prop/minisat/core/Solver.h
@@ -0,0 +1,302 @@
+/****************************************************************************************[Solver.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef Solver_h
+#define Solver_h
+
+#include <cstdio>
+
+#include "Vec.h"
+#include "Heap.h"
+#include "Alg.h"
+
+#include "SolverTypes.h"
+
+
+//=================================================================================================
+// Solver -- the main class:
+
+
+class Solver {
+public:
+
+    // Constructor/Destructor:
+    //
+    Solver();
+    ~Solver();
+
+    // Problem specification:
+    //
+    Var     newVar    (bool polarity = true, bool dvar = true); // Add a new variable with parameters specifying variable mode.
+    bool    addClause (vec<Lit>& ps);                           // Add a clause to the solver. NOTE! 'ps' may be shrunk by this method!
+
+    // Solving:
+    //
+    bool    simplify     ();                        // Removes already satisfied clauses.
+    bool    solve        (const vec<Lit>& assumps); // Search for a model that respects a given set of assumptions.
+    bool    solve        ();                        // Search without assumptions.
+    bool    okay         () const;                  // FALSE means solver is in a conflicting state
+
+    // Variable mode:
+    // 
+    void    setPolarity    (Var v, bool b); // Declare which polarity the decision heuristic should use for a variable. Requires mode 'polarity_user'.
+    void    setDecisionVar (Var v, bool b); // Declare if a variable should be eligible for selection in the decision heuristic.
+
+    // Read state:
+    //
+    lbool   value      (Var x) const;       // The current value of a variable.
+    lbool   value      (Lit p) const;       // The current value of a literal.
+    lbool   modelValue (Lit p) const;       // The value of a literal in the last model. The last call to solve must have been satisfiable.
+    int     nAssigns   ()      const;       // The current number of assigned literals.
+    int     nClauses   ()      const;       // The current number of original clauses.
+    int     nLearnts   ()      const;       // The current number of learnt clauses.
+    int     nVars      ()      const;       // The current number of variables.
+
+    // Extra results: (read-only member variable)
+    //
+    vec<lbool> model;             // If problem is satisfiable, this vector contains the model (if any).
+    vec<Lit>   conflict;          // If problem is unsatisfiable (possibly under assumptions),
+                                  // this vector represent the final conflict clause expressed in the assumptions.
+
+    // Mode of operation:
+    //
+    double    var_decay;          // Inverse of the variable activity decay factor.                                            (default 1 / 0.95)
+    double    clause_decay;       // Inverse of the clause activity decay factor.                                              (1 / 0.999)
+    double    random_var_freq;    // The frequency with which the decision heuristic tries to choose a random variable.        (default 0.02)
+    int       restart_first;      // The initial restart limit.                                                                (default 100)
+    double    restart_inc;        // The factor with which the restart limit is multiplied in each restart.                    (default 1.5)
+    double    learntsize_factor;  // The intitial limit for learnt clauses is a factor of the original clauses.                (default 1 / 3)
+    double    learntsize_inc;     // The limit for learnt clauses is multiplied with this factor each restart.                 (default 1.1)
+    bool      expensive_ccmin;    // Controls conflict clause minimization.                                                    (default TRUE)
+    int       polarity_mode;      // Controls which polarity the decision heuristic chooses. See enum below for allowed modes. (default polarity_false)
+    int       verbosity;          // Verbosity level. 0=silent, 1=some progress report                                         (default 0)
+
+    enum { polarity_true = 0, polarity_false = 1, polarity_user = 2, polarity_rnd = 3 };
+
+    // Statistics: (read-only member variable)
+    //
+    uint64_t starts, decisions, rnd_decisions, propagations, conflicts;
+    uint64_t clauses_literals, learnts_literals, max_literals, tot_literals;
+
+protected:
+
+    // Helper structures:
+    //
+    struct VarOrderLt {
+        const vec<double>&  activity;
+        bool operator () (Var x, Var y) const { return activity[x] > activity[y]; }
+        VarOrderLt(const vec<double>&  act) : activity(act) { }
+    };
+
+    friend class VarFilter;
+    struct VarFilter {
+        const Solver& s;
+        VarFilter(const Solver& _s) : s(_s) {}
+        bool operator()(Var v) const { return toLbool(s.assigns[v]) == l_Undef && s.decision_var[v]; }
+    };
+
+    // Solver state:
+    //
+    bool                ok;               // If FALSE, the constraints are already unsatisfiable. No part of the solver state may be used!
+    vec<Clause*>        clauses;          // List of problem clauses.
+    vec<Clause*>        learnts;          // List of learnt clauses.
+    double              cla_inc;          // Amount to bump next clause with.
+    vec<double>         activity;         // A heuristic measurement of the activity of a variable.
+    double              var_inc;          // Amount to bump next variable with.
+    vec<vec<Clause*> >  watches;          // 'watches[lit]' is a list of constraints watching 'lit' (will go there if literal becomes true).
+    vec<char>           assigns;          // The current assignments (lbool:s stored as char:s).
+    vec<char>           polarity;         // The preferred polarity of each variable.
+    vec<char>           decision_var;     // Declares if a variable is eligible for selection in the decision heuristic.
+    vec<Lit>            trail;            // Assignment stack; stores all assigments made in the order they were made.
+    vec<int>            trail_lim;        // Separator indices for different decision levels in 'trail'.
+    vec<Clause*>        reason;           // 'reason[var]' is the clause that implied the variables current value, or 'NULL' if none.
+    vec<int>            level;            // 'level[var]' contains the level at which the assignment was made.
+    int                 qhead;            // Head of queue (as index into the trail -- no more explicit propagation queue in MiniSat).
+    int                 simpDB_assigns;   // Number of top-level assignments since last execution of 'simplify()'.
+    int64_t             simpDB_props;     // Remaining number of propagations that must be made before next execution of 'simplify()'.
+    vec<Lit>            assumptions;      // Current set of assumptions provided to solve by the user.
+    Heap<VarOrderLt>    order_heap;       // A priority queue of variables ordered with respect to the variable activity.
+    double              random_seed;      // Used by the random variable selection.
+    double              progress_estimate;// Set by 'search()'.
+    bool                remove_satisfied; // Indicates whether possibly inefficient linear scan for satisfied clauses should be performed in 'simplify'.
+
+    // Temporaries (to reduce allocation overhead). Each variable is prefixed by the method in which it is
+    // used, exept 'seen' wich is used in several places.
+    //
+    vec<char>           seen;
+    vec<Lit>            analyze_stack;
+    vec<Lit>            analyze_toclear;
+    vec<Lit>            add_tmp;
+
+    // Main internal methods:
+    //
+    void     insertVarOrder   (Var x);                                                 // Insert a variable in the decision order priority queue.
+    Lit      pickBranchLit    (int polarity_mode, double random_var_freq);             // Return the next decision variable.
+    void     newDecisionLevel ();                                                      // Begins a new decision level.
+    void     uncheckedEnqueue (Lit p, Clause* from = NULL);                            // Enqueue a literal. Assumes value of literal is undefined.
+    bool     enqueue          (Lit p, Clause* from = NULL);                            // Test if fact 'p' contradicts current state, enqueue otherwise.
+    Clause*  propagate        ();                                                      // Perform unit propagation. Returns possibly conflicting clause.
+    void     cancelUntil      (int level);                                             // Backtrack until a certain level.
+    void     analyze          (Clause* confl, vec<Lit>& out_learnt, int& out_btlevel); // (bt = backtrack)
+    void     analyzeFinal     (Lit p, vec<Lit>& out_conflict);                         // COULD THIS BE IMPLEMENTED BY THE ORDINARIY "analyze" BY SOME REASONABLE GENERALIZATION?
+    bool     litRedundant     (Lit p, uint32_t abstract_levels);                       // (helper method for 'analyze()')
+    lbool    search           (int nof_conflicts, int nof_learnts);                    // Search for a given number of conflicts.
+    void     reduceDB         ();                                                      // Reduce the set of learnt clauses.
+    void     removeSatisfied  (vec<Clause*>& cs);                                      // Shrink 'cs' to contain only non-satisfied clauses.
+
+    // Maintaining Variable/Clause activity:
+    //
+    void     varDecayActivity ();                      // Decay all variables with the specified factor. Implemented by increasing the 'bump' value instead.
+    void     varBumpActivity  (Var v);                 // Increase a variable with the current 'bump' value.
+    void     claDecayActivity ();                      // Decay all clauses with the specified factor. Implemented by increasing the 'bump' value instead.
+    void     claBumpActivity  (Clause& c);             // Increase a clause with the current 'bump' value.
+
+    // Operations on clauses:
+    //
+    void     attachClause     (Clause& c);             // Attach a clause to watcher lists.
+    void     detachClause     (Clause& c);             // Detach a clause to watcher lists.
+    void     removeClause     (Clause& c);             // Detach and free a clause.
+    bool     locked           (const Clause& c) const; // Returns TRUE if a clause is a reason for some implication in the current state.
+    bool     satisfied        (const Clause& c) const; // Returns TRUE if a clause is satisfied in the current state.
+
+    // Misc:
+    //
+    int      decisionLevel    ()      const; // Gives the current decisionlevel.
+    uint32_t abstractLevel    (Var x) const; // Used to represent an abstraction of sets of decision levels.
+    double   progressEstimate ()      const; // DELETE THIS ?? IT'S NOT VERY USEFUL ...
+
+    // Debug:
+    void     printLit         (Lit l);
+    template<class C>
+    void     printClause      (const C& c);
+    void     verifyModel      ();
+    void     checkLiteralCount();
+
+    // Static helpers:
+    //
+
+    // Returns a random float 0 <= x < 1. Seed must never be 0.
+    static inline double drand(double& seed) {
+        seed *= 1389796;
+        int q = (int)(seed / 2147483647);
+        seed -= (double)q * 2147483647;
+        return seed / 2147483647; }
+
+    // Returns a random integer 0 <= x < size. Seed must never be 0.
+    static inline int irand(double& seed, int size) {
+        return (int)(drand(seed) * size); }
+};
+
+
+//=================================================================================================
+// Implementation of inline methods:
+
+
+inline void Solver::insertVarOrder(Var x) {
+    if (!order_heap.inHeap(x) && decision_var[x]) order_heap.insert(x); }
+
+inline void Solver::varDecayActivity() { var_inc *= var_decay; }
+inline void Solver::varBumpActivity(Var v) {
+    if ( (activity[v] += var_inc) > 1e100 ) {
+        // Rescale:
+        for (int i = 0; i < nVars(); i++)
+            activity[i] *= 1e-100;
+        var_inc *= 1e-100; }
+
+    // Update order_heap with respect to new activity:
+    if (order_heap.inHeap(v))
+        order_heap.decrease(v); }
+
+inline void Solver::claDecayActivity() { cla_inc *= clause_decay; }
+inline void Solver::claBumpActivity (Clause& c) {
+        if ( (c.activity() += cla_inc) > 1e20 ) {
+            // Rescale:
+            for (int i = 0; i < learnts.size(); i++)
+                learnts[i]->activity() *= 1e-20;
+            cla_inc *= 1e-20; } }
+
+inline bool     Solver::enqueue         (Lit p, Clause* from)   { return value(p) != l_Undef ? value(p) != l_False : (uncheckedEnqueue(p, from), true); }
+inline bool     Solver::locked          (const Clause& c) const { return reason[var(c[0])] == &c && value(c[0]) == l_True; }
+inline void     Solver::newDecisionLevel()                      { trail_lim.push(trail.size()); }
+
+inline int      Solver::decisionLevel ()      const   { return trail_lim.size(); }
+inline uint32_t Solver::abstractLevel (Var x) const   { return 1 << (level[x] & 31); }
+inline lbool    Solver::value         (Var x) const   { return toLbool(assigns[x]); }
+inline lbool    Solver::value         (Lit p) const   { return toLbool(assigns[var(p)]) ^ sign(p); }
+inline lbool    Solver::modelValue    (Lit p) const   { return model[var(p)] ^ sign(p); }
+inline int      Solver::nAssigns      ()      const   { return trail.size(); }
+inline int      Solver::nClauses      ()      const   { return clauses.size(); }
+inline int      Solver::nLearnts      ()      const   { return learnts.size(); }
+inline int      Solver::nVars         ()      const   { return assigns.size(); }
+inline void     Solver::setPolarity   (Var v, bool b) { polarity    [v] = (char)b; }
+inline void     Solver::setDecisionVar(Var v, bool b) { decision_var[v] = (char)b; if (b) { insertVarOrder(v); } }
+inline bool     Solver::solve         ()              { vec<Lit> tmp; return solve(tmp); }
+inline bool     Solver::okay          ()      const   { return ok; }
+
+
+
+//=================================================================================================
+// Debug + etc:
+
+
+#define reportf(format, args...) ( fflush(stdout), fprintf(stderr, format, ## args), fflush(stderr) )
+
+static inline void logLit(FILE* f, Lit l)
+{
+    fprintf(f, "%sx%d", sign(l) ? "~" : "", var(l)+1);
+}
+
+static inline void logLits(FILE* f, const vec<Lit>& ls)
+{
+    fprintf(f, "[ ");
+    if (ls.size() > 0){
+        logLit(f, ls[0]);
+        for (int i = 1; i < ls.size(); i++){
+            fprintf(f, ", ");
+            logLit(f, ls[i]);
+        }
+    }
+    fprintf(f, "] ");
+}
+
+static inline const char* showBool(bool b) { return b ? "true" : "false"; }
+
+
+// Just like 'assert()' but expression will be evaluated in the release version as well.
+static inline void check(bool expr) { assert(expr); }
+
+
+inline void Solver::printLit(Lit l)
+{
+    reportf("%s%d:%c", sign(l) ? "-" : "", var(l)+1, value(l) == l_True ? '1' : (value(l) == l_False ? '0' : 'X'));
+}
+
+
+template<class C>
+inline void Solver::printClause(const C& c)
+{
+    for (int i = 0; i < c.size(); i++){
+        printLit(c[i]);
+        fprintf(stderr, " ");
+    }
+}
+
+
+//=================================================================================================
+#endif
diff --git a/src/prop/minisat/core/SolverTypes.h b/src/prop/minisat/core/SolverTypes.h
new file mode 100644
index 000000000..47e302390
--- /dev/null
+++ b/src/prop/minisat/core/SolverTypes.h
@@ -0,0 +1,197 @@
+/***********************************************************************************[SolverTypes.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+
+#ifndef SolverTypes_h
+#define SolverTypes_h
+
+#include <cassert>
+#include <stdint.h>
+
+//=================================================================================================
+// Variables, literals, lifted booleans, clauses:
+
+
+// NOTE! Variables are just integers. No abstraction here. They should be chosen from 0..N,
+// so that they can be used as array indices.
+
+typedef int Var;
+#define var_Undef (-1)
+
+
+class Lit {
+    int     x;
+ public:
+    Lit() : x(2*var_Undef)                                              { }   // (lit_Undef)
+    explicit Lit(Var var, bool sign = false) : x((var+var) + (int)sign) { }
+
+    // Don't use these for constructing/deconstructing literals. Use the normal constructors instead.
+    friend int  toInt       (Lit p);  // Guarantees small, positive integers suitable for array indexing.
+    friend Lit  toLit       (int i);  // Inverse of 'toInt()'
+    friend Lit  operator   ~(Lit p);
+    friend bool sign        (Lit p);
+    friend int  var         (Lit p);
+    friend Lit  unsign      (Lit p);
+    friend Lit  id          (Lit p, bool sgn);
+
+    bool operator == (Lit p) const { return x == p.x; }
+    bool operator != (Lit p) const { return x != p.x; }
+    bool operator <  (Lit p) const { return x < p.x;  } // '<' guarantees that p, ~p are adjacent in the ordering.
+};
+
+inline  int  toInt       (Lit p)           { return p.x; }
+inline  Lit  toLit       (int i)           { Lit p; p.x = i; return p; }
+inline  Lit  operator   ~(Lit p)           { Lit q; q.x = p.x ^ 1; return q; }
+inline  bool sign        (Lit p)           { return p.x & 1; }
+inline  int  var         (Lit p)           { return p.x >> 1; }
+inline  Lit  unsign      (Lit p)           { Lit q; q.x = p.x & ~1; return q; }
+inline  Lit  id          (Lit p, bool sgn) { Lit q; q.x = p.x ^ (int)sgn; return q; }
+
+const Lit lit_Undef(var_Undef, false);  // }- Useful special constants.
+const Lit lit_Error(var_Undef, true );  // }
+
+
+//=================================================================================================
+// Lifted booleans:
+
+
+class lbool {
+    char     value;
+    explicit lbool(int v) : value(v) { }
+
+public:
+    lbool()       : value(0) { }
+    lbool(bool x) : value((int)x*2-1) { }
+    int toInt(void) const { return value; }
+
+    bool  operator == (lbool b) const { return value == b.value; }
+    bool  operator != (lbool b) const { return value != b.value; }
+    lbool operator ^ (bool b) const { return b ? lbool(-value) : lbool(value); }
+
+    friend int   toInt  (lbool l);
+    friend lbool toLbool(int   v);
+};
+inline int   toInt  (lbool l) { return l.toInt(); }
+inline lbool toLbool(int   v) { return lbool(v);  }
+
+const lbool l_True  = toLbool( 1);
+const lbool l_False = toLbool(-1);
+const lbool l_Undef = toLbool( 0);
+
+//=================================================================================================
+// Clause -- a simple class for representing a clause:
+
+
+class Clause {
+    uint32_t size_etc;
+    union { float act; uint32_t abst; } extra;
+    Lit     data[0];
+
+public:
+    void calcAbstraction() {
+        uint32_t abstraction = 0;
+        for (int i = 0; i < size(); i++)
+            abstraction |= 1 << (var(data[i]) & 31);
+        extra.abst = abstraction;  }
+
+    // NOTE: This constructor cannot be used directly (doesn't allocate enough memory).
+    template<class V>
+    Clause(const V& ps, bool learnt) {
+        size_etc = (ps.size() << 3) | (uint32_t)learnt;
+        for (int i = 0; i < ps.size(); i++) data[i] = ps[i];
+        if (learnt) extra.act = 0; else calcAbstraction(); }
+
+    // -- use this function instead:
+    template<class V>
+    friend Clause* Clause_new(const V& ps, bool learnt = false) {
+        assert(sizeof(Lit)      == sizeof(uint32_t));
+        assert(sizeof(float)    == sizeof(uint32_t));
+        void* mem = malloc(sizeof(Clause) + sizeof(uint32_t)*(ps.size()));
+        return new (mem) Clause(ps, learnt); }
+
+    int          size        ()      const   { return size_etc >> 3; }
+    void         shrink      (int i)         { assert(i <= size()); size_etc = (((size_etc >> 3) - i) << 3) | (size_etc & 7); }
+    void         pop         ()              { shrink(1); }
+    bool         learnt      ()      const   { return size_etc & 1; }
+    uint32_t     mark        ()      const   { return (size_etc >> 1) & 3; }
+    void         mark        (uint32_t m)    { size_etc = (size_etc & ~6) | ((m & 3) << 1); }
+    const Lit&   last        ()      const   { return data[size()-1]; }
+
+    // NOTE: somewhat unsafe to change the clause in-place! Must manually call 'calcAbstraction' afterwards for
+    //       subsumption operations to behave correctly.
+    Lit&         operator [] (int i)         { return data[i]; }
+    Lit          operator [] (int i) const   { return data[i]; }
+    operator const Lit* (void) const         { return data; }
+
+    float&       activity    ()              { return extra.act; }
+    uint32_t     abstraction () const { return extra.abst; }
+
+    Lit          subsumes    (const Clause& other) const;
+    void         strengthen  (Lit p);
+};
+
+
+/*_________________________________________________________________________________________________
+|
+|  subsumes : (other : const Clause&)  ->  Lit
+|  
+|  Description:
+|       Checks if clause subsumes 'other', and at the same time, if it can be used to simplify 'other'
+|       by subsumption resolution.
+|  
+|    Result:
+|       lit_Error  - No subsumption or simplification
+|       lit_Undef  - Clause subsumes 'other'
+|       p          - The literal p can be deleted from 'other'
+|________________________________________________________________________________________________@*/
+inline Lit Clause::subsumes(const Clause& other) const
+{
+    if (other.size() < size() || (extra.abst & ~other.extra.abst) != 0)
+        return lit_Error;
+
+    Lit        ret = lit_Undef;
+    const Lit* c  = (const Lit*)(*this);
+    const Lit* d  = (const Lit*)other;
+
+    for (int i = 0; i < size(); i++) {
+        // search for c[i] or ~c[i]
+        for (int j = 0; j < other.size(); j++)
+            if (c[i] == d[j])
+                goto ok;
+            else if (ret == lit_Undef && c[i] == ~d[j]){
+                ret = c[i];
+                goto ok;
+            }
+
+        // did not find it
+        return lit_Error;
+    ok:;
+    }
+
+    return ret;
+}
+
+
+inline void Clause::strengthen(Lit p)
+{
+    remove(*this, p);
+    calcAbstraction();
+}
+
+#endif
diff --git a/src/prop/minisat/mtl/Alg.h b/src/prop/minisat/mtl/Alg.h
new file mode 100644
index 000000000..240962dfc
--- /dev/null
+++ b/src/prop/minisat/mtl/Alg.h
@@ -0,0 +1,57 @@
+/*******************************************************************************************[Alg.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef Alg_h
+#define Alg_h
+
+//=================================================================================================
+// Useful functions on vectors
+
+
+#if 1
+template<class V, class T>
+static inline void remove(V& ts, const T& t)
+{
+    int j = 0;
+    for (; j < ts.size() && ts[j] != t; j++);
+    assert(j < ts.size());
+    for (; j < ts.size()-1; j++) ts[j] = ts[j+1];
+    ts.pop();
+}
+#else
+template<class V, class T>
+static inline void remove(V& ts, const T& t)
+{
+    int j = 0;
+    for (; j < ts.size() && ts[j] != t; j++);
+    assert(j < ts.size());
+    ts[j] = ts.last();
+    ts.pop();
+}
+#endif
+
+template<class V, class T>
+static inline bool find(V& ts, const T& t)
+{
+    int j = 0;
+    for (; j < ts.size() && ts[j] != t; j++);
+    return j < ts.size();
+}
+
+#endif
diff --git a/src/prop/minisat/mtl/BasicHeap.h b/src/prop/minisat/mtl/BasicHeap.h
new file mode 100644
index 000000000..556d98f84
--- /dev/null
+++ b/src/prop/minisat/mtl/BasicHeap.h
@@ -0,0 +1,98 @@
+/******************************************************************************************[Heap.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef BasicHeap_h
+#define BasicHeap_h
+
+#include "Vec.h"
+
+//=================================================================================================
+// A heap implementation with support for decrease/increase key.
+
+
+template<class Comp>
+class BasicHeap {
+    Comp     lt;
+    vec<int> heap;     // heap of ints
+
+    // Index "traversal" functions
+    static inline int left  (int i) { return i*2+1; }
+    static inline int right (int i) { return (i+1)*2; }
+    static inline int parent(int i) { return (i-1) >> 1; }
+
+    inline void percolateUp(int i)
+    {
+        int x = heap[i];
+        while (i != 0 && lt(x, heap[parent(i)])){
+            heap[i]          = heap[parent(i)];
+            i                = parent(i);
+        }
+        heap   [i] = x;
+    }
+
+
+    inline void percolateDown(int i)
+    {
+        int x = heap[i];
+        while (left(i) < heap.size()){
+            int child = right(i) < heap.size() && lt(heap[right(i)], heap[left(i)]) ? right(i) : left(i);
+            if (!lt(heap[child], x)) break;
+            heap[i]          = heap[child];
+            i                = child;
+        }
+        heap[i] = x;
+    }
+
+
+    bool heapProperty(int i) {
+        return i >= heap.size()
+            || ((i == 0 || !lt(heap[i], heap[parent(i)])) && heapProperty(left(i)) && heapProperty(right(i))); }
+
+
+  public:
+    BasicHeap(const C& c) : comp(c) { }
+
+    int  size      ()                     const { return heap.size(); }
+    bool empty     ()                     const { return heap.size() == 0; }
+    int  operator[](int index)            const { return heap[index+1]; }
+    void clear     (bool dealloc = false)       { heap.clear(dealloc); }
+    void insert    (int n)                      { heap.push(n); percolateUp(heap.size()-1); }
+
+
+    int  removeMin() {
+        int r   = heap[0];
+        heap[0] = heap.last();
+        heap.pop();
+        if (heap.size() > 1) percolateDown(0);
+        return r; 
+    }
+
+
+    // DEBUG: consistency checking
+    bool heapProperty() {
+        return heapProperty(1); }
+
+
+    // COMPAT: should be removed
+    int  getmin    ()      { return removeMin(); }
+};
+
+
+//=================================================================================================
+#endif
diff --git a/src/prop/minisat/mtl/BoxedVec.h b/src/prop/minisat/mtl/BoxedVec.h
new file mode 100644
index 000000000..bddf41008
--- /dev/null
+++ b/src/prop/minisat/mtl/BoxedVec.h
@@ -0,0 +1,147 @@
+/*******************************************************************************************[Vec.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef BoxedVec_h
+#define BoxedVec_h
+
+#include <cstdlib>
+#include <cassert>
+#include <new>
+
+//=================================================================================================
+// Automatically resizable arrays
+//
+// NOTE! Don't use this vector on datatypes that cannot be re-located in memory (with realloc)
+
+template<class T>
+class bvec {
+
+    static inline int imin(int x, int y) {
+        int mask = (x-y) >> (sizeof(int)*8-1);
+        return (x&mask) + (y&(~mask)); }
+
+    static inline int imax(int x, int y) {
+        int mask = (y-x) >> (sizeof(int)*8-1);
+        return (x&mask) + (y&(~mask)); }
+
+    struct Vec_t {
+        int sz;
+        int cap;
+        T   data[0];
+
+        static Vec_t* alloc(Vec_t* x, int size){
+            x = (Vec_t*)realloc((void*)x, sizeof(Vec_t) + sizeof(T)*size);
+            x->cap = size;
+            return x;
+        }
+        
+    };
+
+    Vec_t* ref;
+
+    static const int init_size = 2;
+    static int   nextSize (int current) { return (current * 3 + 1) >> 1; }
+    static int   fitSize  (int needed)  { int x; for (x = init_size; needed > x; x = nextSize(x)); return x; }
+
+    void fill (int size) {
+        assert(ref != NULL);
+        for (T* i = ref->data; i < ref->data + size; i++)
+            new (i) T();
+    }
+
+    void fill (int size, const T& pad) {
+        assert(ref != NULL);
+        for (T* i = ref->data; i < ref->data + size; i++)
+            new (i) T(pad);
+    }
+
+    // Don't allow copying (error prone):
+    altvec<T>&  operator = (altvec<T>& other) { assert(0); }
+    altvec (altvec<T>& other)                  { assert(0); }
+
+public:
+    void     clear  (bool dealloc = false) { 
+        if (ref != NULL){
+            for (int i = 0; i < ref->sz; i++) 
+                (*ref).data[i].~T();
+
+            if (dealloc) { 
+                free(ref); ref = NULL; 
+            }else 
+                ref->sz = 0;
+        } 
+    }
+
+    // Constructors:
+    altvec(void)                   : ref (NULL) { }
+    altvec(int size)               : ref (Vec_t::alloc(NULL, fitSize(size))) { fill(size);      ref->sz = size; }
+    altvec(int size, const T& pad) : ref (Vec_t::alloc(NULL, fitSize(size))) { fill(size, pad); ref->sz = size; }
+   ~altvec(void) { clear(true); }
+
+    // Ownership of underlying array:
+    operator T*       (void)           { return ref->data; }     // (unsafe but convenient)
+    operator const T* (void) const     { return ref->data; }
+
+    // Size operations:
+    int      size   (void) const       { return ref != NULL ? ref->sz : 0; }
+
+    void     pop    (void)             { assert(ref != NULL && ref->sz > 0); int last = --ref->sz; ref->data[last].~T(); }
+    void     push   (const T& elem) {
+        int size = ref != NULL ? ref->sz  : 0;
+        int cap  = ref != NULL ? ref->cap : 0;
+        if (size == cap){
+            cap = cap != 0 ? nextSize(cap) : init_size;
+            ref = Vec_t::alloc(ref, cap); 
+        }
+        //new (&ref->data[size]) T(elem); 
+        ref->data[size] = elem; 
+        ref->sz = size+1; 
+    }
+
+    void     push   () {
+        int size = ref != NULL ? ref->sz  : 0;
+        int cap  = ref != NULL ? ref->cap : 0;
+        if (size == cap){
+            cap = cap != 0 ? nextSize(cap) : init_size;
+            ref = Vec_t::alloc(ref, cap); 
+        }
+        new (&ref->data[size]) T(); 
+        ref->sz = size+1; 
+    }
+
+    void     shrink (int nelems)             { for (int i = 0; i < nelems; i++) pop(); }
+    void     shrink_(int nelems)             { for (int i = 0; i < nelems; i++) pop(); }
+    void     growTo (int size)               { while (this->size() < size) push(); }
+    void     growTo (int size, const T& pad) { while (this->size() < size) push(pad); }
+    void     capacity (int size)             { growTo(size); }
+
+    const T& last  (void) const              { return ref->data[ref->sz-1]; }
+    T&       last  (void)                    { return ref->data[ref->sz-1]; }
+
+    // Vector interface:
+    const T& operator [] (int index) const  { return ref->data[index]; }
+    T&       operator [] (int index)        { return ref->data[index]; }
+
+    void copyTo(altvec<T>& copy) const { copy.clear(); for (int i = 0; i < size(); i++) copy.push(ref->data[i]); }
+    void moveTo(altvec<T>& dest) { dest.clear(true); dest.ref = ref; ref = NULL; }
+
+};
+
+
+#endif
diff --git a/src/prop/minisat/mtl/Heap.h b/src/prop/minisat/mtl/Heap.h
new file mode 100644
index 000000000..b07ccd152
--- /dev/null
+++ b/src/prop/minisat/mtl/Heap.h
@@ -0,0 +1,169 @@
+/******************************************************************************************[Heap.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef Heap_h
+#define Heap_h
+
+#include "Vec.h"
+
+//=================================================================================================
+// A heap implementation with support for decrease/increase key.
+
+
+template<class Comp>
+class Heap {
+    Comp     lt;
+    vec<int> heap;     // heap of ints
+    vec<int> indices;  // int -> index in heap
+
+    // Index "traversal" functions
+    static inline int left  (int i) { return i*2+1; }
+    static inline int right (int i) { return (i+1)*2; }
+    static inline int parent(int i) { return (i-1) >> 1; }
+
+
+    inline void percolateUp(int i)
+    {
+        int x = heap[i];
+        while (i != 0 && lt(x, heap[parent(i)])){
+            heap[i]          = heap[parent(i)];
+            indices[heap[i]] = i;
+            i                = parent(i);
+        }
+        heap   [i] = x;
+        indices[x] = i;
+    }
+
+
+    inline void percolateDown(int i)
+    {
+        int x = heap[i];
+        while (left(i) < heap.size()){
+            int child = right(i) < heap.size() && lt(heap[right(i)], heap[left(i)]) ? right(i) : left(i);
+            if (!lt(heap[child], x)) break;
+            heap[i]          = heap[child];
+            indices[heap[i]] = i;
+            i                = child;
+        }
+        heap   [i] = x;
+        indices[x] = i;
+    }
+
+
+    bool heapProperty (int i) const {
+        return i >= heap.size()
+            || ((i == 0 || !lt(heap[i], heap[parent(i)])) && heapProperty(left(i)) && heapProperty(right(i))); }
+
+
+  public:
+    Heap(const Comp& c) : lt(c) { }
+
+    int  size      ()          const { return heap.size(); }
+    bool empty     ()          const { return heap.size() == 0; }
+    bool inHeap    (int n)     const { return n < indices.size() && indices[n] >= 0; }
+    int  operator[](int index) const { assert(index < heap.size()); return heap[index]; }
+
+    void decrease  (int n) { assert(inHeap(n)); percolateUp(indices[n]); }
+
+    // RENAME WHEN THE DEPRECATED INCREASE IS REMOVED.
+    void increase_ (int n) { assert(inHeap(n)); percolateDown(indices[n]); }
+
+
+    void insert(int n)
+    {
+        indices.growTo(n+1, -1);
+        assert(!inHeap(n));
+
+        indices[n] = heap.size();
+        heap.push(n);
+        percolateUp(indices[n]); 
+    }
+
+
+    int  removeMin()
+    {
+        int x            = heap[0];
+        heap[0]          = heap.last();
+        indices[heap[0]] = 0;
+        indices[x]       = -1;
+        heap.pop();
+        if (heap.size() > 1) percolateDown(0);
+        return x; 
+    }
+
+
+    void clear(bool dealloc = false) 
+    { 
+        for (int i = 0; i < heap.size(); i++)
+            indices[heap[i]] = -1;
+#ifdef NDEBUG
+        for (int i = 0; i < indices.size(); i++)
+            assert(indices[i] == -1);
+#endif
+        heap.clear(dealloc); 
+    }
+
+
+    // Fool proof variant of insert/decrease/increase
+    void update (int n)
+    {
+        if (!inHeap(n))
+            insert(n);
+        else {
+            percolateUp(indices[n]);
+            percolateDown(indices[n]);
+        }
+    }
+
+
+    // Delete elements from the heap using a given filter function (-object).
+    // *** this could probaly be replaced with a more general "buildHeap(vec<int>&)" method ***
+    template <class F>
+    void filter(const F& filt) {
+        int i,j;
+        for (i = j = 0; i < heap.size(); i++)
+            if (filt(heap[i])){
+                heap[j]          = heap[i];
+                indices[heap[i]] = j++;
+            }else
+                indices[heap[i]] = -1;
+
+        heap.shrink(i - j);
+        for (int i = heap.size() / 2 - 1; i >= 0; i--)
+            percolateDown(i);
+
+        assert(heapProperty());
+    }
+
+
+    // DEBUG: consistency checking
+    bool heapProperty() const {
+        return heapProperty(1); }
+
+
+    // COMPAT: should be removed
+    void setBounds (int n) { }
+    void increase  (int n) { decrease(n); }
+    int  getmin    ()      { return removeMin(); }
+
+};
+
+
+//=================================================================================================
+#endif
diff --git a/src/prop/minisat/mtl/Map.h b/src/prop/minisat/mtl/Map.h
new file mode 100644
index 000000000..b6d76a31c
--- /dev/null
+++ b/src/prop/minisat/mtl/Map.h
@@ -0,0 +1,118 @@
+/*******************************************************************************************[Map.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef Map_h
+#define Map_h
+
+#include <stdint.h>
+
+#include "Vec.h"
+
+//=================================================================================================
+// Default hash/equals functions
+//
+
+template<class K> struct Hash  { uint32_t operator()(const K& k)               const { return hash(k);  } };
+template<class K> struct Equal { bool     operator()(const K& k1, const K& k2) const { return k1 == k2; } };
+
+template<class K> struct DeepHash  { uint32_t operator()(const K* k)               const { return hash(*k);  } };
+template<class K> struct DeepEqual { bool     operator()(const K* k1, const K* k2) const { return *k1 == *k2; } };
+
+//=================================================================================================
+// Some primes
+//
+
+static const int nprimes          = 25;
+static const int primes [nprimes] = { 31, 73, 151, 313, 643, 1291, 2593, 5233, 10501, 21013, 42073, 84181, 168451, 337219, 674701, 1349473, 2699299, 5398891, 10798093, 21596719, 43193641, 86387383, 172775299, 345550609, 691101253 };
+
+//=================================================================================================
+// Hash table implementation of Maps
+//
+
+template<class K, class D, class H = Hash<K>, class E = Equal<K> >
+class Map {
+    struct Pair { K key; D data; };
+
+    H          hash;
+    E          equals;
+
+    vec<Pair>* table;
+    int        cap;
+    int        size;
+
+    // Don't allow copying (error prone):
+    Map<K,D,H,E>&  operator = (Map<K,D,H,E>& other) { assert(0); }
+                   Map        (Map<K,D,H,E>& other) { assert(0); }
+
+    int32_t index  (const K& k) const { return hash(k) % cap; }
+    void   _insert (const K& k, const D& d) { table[index(k)].push(); table[index(k)].last().key = k; table[index(k)].last().data = d; }
+    void    rehash () {
+        const vec<Pair>* old = table;
+
+        int newsize = primes[0];
+        for (int i = 1; newsize <= cap && i < nprimes; i++)
+           newsize = primes[i];
+
+        table = new vec<Pair>[newsize];
+
+        for (int i = 0; i < cap; i++){
+            for (int j = 0; j < old[i].size(); j++){
+                _insert(old[i][j].key, old[i][j].data); }}
+
+        delete [] old;
+
+        cap = newsize;
+    }
+
+    
+    public:
+
+     Map () : table(NULL), cap(0), size(0) {}
+     Map (const H& h, const E& e) : Map(), hash(h), equals(e) {}
+    ~Map () { delete [] table; }
+
+    void insert (const K& k, const D& d) { if (size+1 > cap / 2) rehash(); _insert(k, d); size++; }
+    bool peek   (const K& k, D& d) {
+        if (size == 0) return false;
+        const vec<Pair>& ps = table[index(k)];
+        for (int i = 0; i < ps.size(); i++)
+            if (equals(ps[i].key, k)){
+                d = ps[i].data;
+                return true; } 
+        return false;
+    }
+
+    void remove (const K& k) {
+        assert(table != NULL);
+        vec<Pair>& ps = table[index(k)];
+        int j = 0;
+        for (; j < ps.size() && !equals(ps[j].key, k); j++);
+        assert(j < ps.size());
+        ps[j] = ps.last();
+        ps.pop();
+    }
+
+    void clear  () {
+        cap = size = 0;
+        delete [] table;
+        table = NULL;
+    }
+};
+
+#endif
diff --git a/src/prop/minisat/mtl/Queue.h b/src/prop/minisat/mtl/Queue.h
new file mode 100644
index 000000000..2cc110ce9
--- /dev/null
+++ b/src/prop/minisat/mtl/Queue.h
@@ -0,0 +1,82 @@
+/*****************************************************************************************[Queue.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef Queue_h
+#define Queue_h
+
+#include "Vec.h"
+
+//=================================================================================================
+
+
+template <class T>
+class Queue {
+    vec<T>  elems;
+    int     first;
+
+public:
+    Queue(void) : first(0) { }
+
+    void insert(T x)   { elems.push(x); }
+    T    peek  () const { return elems[first]; }
+    void pop   () { first++; }
+
+    void clear(bool dealloc = false)   { elems.clear(dealloc); first = 0; }
+    int  size(void)    { return elems.size() - first; }
+
+    //bool has(T x) { for (int i = first; i < elems.size(); i++) if (elems[i] == x) return true; return false; }
+
+    const T& operator [] (int index) const  { return elems[first + index]; }
+
+};
+
+//template<class T>
+//class Queue {
+//    vec<T>  buf;
+//    int     first;
+//    int     end;
+//
+//public:
+//    typedef T Key;
+//
+//    Queue() : buf(1), first(0), end(0) {}
+//
+//    void clear () { buf.shrinkTo(1); first = end = 0; }
+//    int  size  () { return (end >= first) ? end - first : end - first + buf.size(); }
+//
+//    T    peek  () { assert(first != end); return buf[first]; }
+//    void pop   () { assert(first != end); first++; if (first == buf.size()) first = 0; }
+//    void insert(T elem) {   // INVARIANT: buf[end] is always unused
+//        buf[end++] = elem;
+//        if (end == buf.size()) end = 0;
+//        if (first == end){  // Resize:
+//            vec<T>  tmp((buf.size()*3 + 1) >> 1);
+//            //**/printf("queue alloc: %d elems (%.1f MB)\n", tmp.size(), tmp.size() * sizeof(T) / 1000000.0);
+//            int     i = 0;
+//            for (int j = first; j < buf.size(); j++) tmp[i++] = buf[j];
+//            for (int j = 0    ; j < end       ; j++) tmp[i++] = buf[j];
+//            first = 0;
+//            end   = buf.size();
+//            tmp.moveTo(buf);
+//        }
+//    }
+//};
+
+//=================================================================================================
+#endif
diff --git a/src/prop/minisat/mtl/Sort.h b/src/prop/minisat/mtl/Sort.h
new file mode 100644
index 000000000..1f301f5c2
--- /dev/null
+++ b/src/prop/minisat/mtl/Sort.h
@@ -0,0 +1,93 @@
+/******************************************************************************************[Sort.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef Sort_h
+#define Sort_h
+
+#include "Vec.h"
+
+//=================================================================================================
+// Some sorting algorithms for vec's
+
+
+template<class T>
+struct LessThan_default {
+    bool operator () (T x, T y) { return x < y; }
+};
+
+
+template <class T, class LessThan>
+void selectionSort(T* array, int size, LessThan lt)
+{
+    int     i, j, best_i;
+    T       tmp;
+
+    for (i = 0; i < size-1; i++){
+        best_i = i;
+        for (j = i+1; j < size; j++){
+            if (lt(array[j], array[best_i]))
+                best_i = j;
+        }
+        tmp = array[i]; array[i] = array[best_i]; array[best_i] = tmp;
+    }
+}
+template <class T> static inline void selectionSort(T* array, int size) {
+    selectionSort(array, size, LessThan_default<T>()); }
+
+template <class T, class LessThan>
+void sort(T* array, int size, LessThan lt)
+{
+    if (size <= 15)
+        selectionSort(array, size, lt);
+
+    else{
+        T           pivot = array[size / 2];
+        T           tmp;
+        int         i = -1;
+        int         j = size;
+
+        for(;;){
+            do i++; while(lt(array[i], pivot));
+            do j--; while(lt(pivot, array[j]));
+
+            if (i >= j) break;
+
+            tmp = array[i]; array[i] = array[j]; array[j] = tmp;
+        }
+
+        sort(array    , i     , lt);
+        sort(&array[i], size-i, lt);
+    }
+}
+template <class T> static inline void sort(T* array, int size) {
+    sort(array, size, LessThan_default<T>()); }
+
+
+//=================================================================================================
+// For 'vec's:
+
+
+template <class T, class LessThan> void sort(vec<T>& v, LessThan lt) {
+    sort((T*)v, v.size(), lt); }
+template <class T> void sort(vec<T>& v) {
+    sort(v, LessThan_default<T>()); }
+
+
+//=================================================================================================
+#endif
diff --git a/src/prop/minisat/mtl/Vec.h b/src/prop/minisat/mtl/Vec.h
new file mode 100644
index 000000000..e780aa167
--- /dev/null
+++ b/src/prop/minisat/mtl/Vec.h
@@ -0,0 +1,133 @@
+/*******************************************************************************************[Vec.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef Vec_h
+#define Vec_h
+
+#include <cstdlib>
+#include <cassert>
+#include <new>
+
+//=================================================================================================
+// Automatically resizable arrays
+//
+// NOTE! Don't use this vector on datatypes that cannot be re-located in memory (with realloc)
+
+template<class T>
+class vec {
+    T*  data;
+    int sz;
+    int cap;
+
+    void     init(int size, const T& pad);
+    void     grow(int min_cap);
+
+    // Don't allow copying (error prone):
+    vec<T>&  operator = (vec<T>& other) { assert(0); return *this; }
+             vec        (vec<T>& other) { assert(0); }
+
+    static inline int imin(int x, int y) {
+        int mask = (x-y) >> (sizeof(int)*8-1);
+        return (x&mask) + (y&(~mask)); }
+
+    static inline int imax(int x, int y) {
+        int mask = (y-x) >> (sizeof(int)*8-1);
+        return (x&mask) + (y&(~mask)); }
+
+public:
+    // Types:
+    typedef int Key;
+    typedef T   Datum;
+
+    // Constructors:
+    vec(void)                   : data(NULL) , sz(0)   , cap(0)    { }
+    vec(int size)               : data(NULL) , sz(0)   , cap(0)    { growTo(size); }
+    vec(int size, const T& pad) : data(NULL) , sz(0)   , cap(0)    { growTo(size, pad); }
+    vec(T* array, int size)     : data(array), sz(size), cap(size) { }      // (takes ownership of array -- will be deallocated with 'free()')
+   ~vec(void)                                                      { clear(true); }
+
+    // Ownership of underlying array:
+    T*       release  (void)           { T* ret = data; data = NULL; sz = 0; cap = 0; return ret; }
+    operator T*       (void)           { return data; }     // (unsafe but convenient)
+    operator const T* (void) const     { return data; }
+
+    // Size operations:
+    int      size   (void) const       { return sz; }
+    void     shrink (int nelems)       { assert(nelems <= sz); for (int i = 0; i < nelems; i++) sz--, data[sz].~T(); }
+    void     shrink_(int nelems)       { assert(nelems <= sz); sz -= nelems; }
+    void     pop    (void)             { sz--, data[sz].~T(); }
+    void     growTo (int size);
+    void     growTo (int size, const T& pad);
+    void     clear  (bool dealloc = false);
+    void     capacity (int size) { grow(size); }
+
+    // Stack interface:
+#if 1
+    void     push  (void)              { if (sz == cap) { cap = imax(2, (cap*3+1)>>1); data = (T*)realloc(data, cap * sizeof(T)); } new (&data[sz]) T(); sz++; }
+    //void     push  (const T& elem)     { if (sz == cap) { cap = imax(2, (cap*3+1)>>1); data = (T*)realloc(data, cap * sizeof(T)); } new (&data[sz]) T(elem); sz++; }
+    void     push  (const T& elem)     { if (sz == cap) { cap = imax(2, (cap*3+1)>>1); data = (T*)realloc(data, cap * sizeof(T)); } data[sz++] = elem; }
+    void     push_ (const T& elem)     { assert(sz < cap); data[sz++] = elem; }
+#else
+    void     push  (void)              { if (sz == cap) grow(sz+1); new (&data[sz]) T()    ; sz++; }
+    void     push  (const T& elem)     { if (sz == cap) grow(sz+1); new (&data[sz]) T(elem); sz++; }
+#endif
+
+    const T& last  (void) const        { return data[sz-1]; }
+    T&       last  (void)              { return data[sz-1]; }
+
+    // Vector interface:
+    const T& operator [] (int index) const  { return data[index]; }
+    T&       operator [] (int index)        { return data[index]; }
+
+
+    // Duplicatation (preferred instead):
+    void copyTo(vec<T>& copy) const { copy.clear(); copy.growTo(sz); for (int i = 0; i < sz; i++) new (&copy[i]) T(data[i]); }
+    void moveTo(vec<T>& dest) { dest.clear(true); dest.data = data; dest.sz = sz; dest.cap = cap; data = NULL; sz = 0; cap = 0; }
+};
+
+template<class T>
+void vec<T>::grow(int min_cap) {
+    if (min_cap <= cap) return;
+    if (cap == 0) cap = (min_cap >= 2) ? min_cap : 2;
+    else          do cap = (cap*3+1) >> 1; while (cap < min_cap);
+    data = (T*)realloc(data, cap * sizeof(T)); }
+
+template<class T>
+void vec<T>::growTo(int size, const T& pad) {
+    if (sz >= size) return;
+    grow(size);
+    for (int i = sz; i < size; i++) new (&data[i]) T(pad);
+    sz = size; }
+
+template<class T>
+void vec<T>::growTo(int size) {
+    if (sz >= size) return;
+    grow(size);
+    for (int i = sz; i < size; i++) new (&data[i]) T();
+    sz = size; }
+
+template<class T>
+void vec<T>::clear(bool dealloc) {
+    if (data != NULL){
+        for (int i = 0; i < sz; i++) data[i].~T();
+        sz = 0;
+        if (dealloc) free(data), data = NULL, cap = 0; } }
+
+
+#endif
diff --git a/src/prop/minisat/mtl/template.mk b/src/prop/minisat/mtl/template.mk
new file mode 100644
index 000000000..15f023fb3
--- /dev/null
+++ b/src/prop/minisat/mtl/template.mk
@@ -0,0 +1,90 @@
+##
+##  Template makefile for Standard, Profile, Debug, Release, and Release-static versions
+##
+##    eg: "make rs" for a statically linked release version.
+##        "make d"  for a debug version (no optimizations).
+##        "make"    for the standard version (optimized, but with debug information and assertions active)
+
+CSRCS     ?= $(wildcard *.C)
+CHDRS     ?= $(wildcard *.h)
+COBJS     ?= $(addsuffix .o, $(basename $(CSRCS)))
+
+PCOBJS     = $(addsuffix p,  $(COBJS))
+DCOBJS     = $(addsuffix d,  $(COBJS))
+RCOBJS     = $(addsuffix r,  $(COBJS))
+
+EXEC      ?= $(notdir $(shell pwd))
+LIB       ?= $(EXEC)
+
+CXX       ?= g++
+CFLAGS    ?= -Wall
+LFLAGS    ?= -Wall
+
+COPTIMIZE ?= -O3
+
+.PHONY : s p d r rs lib libd clean 
+
+s:	$(EXEC)
+p:	$(EXEC)_profile
+d:	$(EXEC)_debug
+r:	$(EXEC)_release
+rs:	$(EXEC)_static
+lib:	lib$(LIB).a
+libd:	lib$(LIB)d.a
+
+## Compile options
+%.o:			CFLAGS +=$(COPTIMIZE) -ggdb -D DEBUG
+%.op:			CFLAGS +=$(COPTIMIZE) -pg -ggdb -D NDEBUG
+%.od:			CFLAGS +=-O0 -ggdb -D DEBUG # -D INVARIANTS
+%.or:			CFLAGS +=$(COPTIMIZE) -D NDEBUG
+
+## Link options
+$(EXEC):		LFLAGS := -ggdb $(LFLAGS)
+$(EXEC)_profile:	LFLAGS := -ggdb -pg $(LFLAGS)
+$(EXEC)_debug:		LFLAGS := -ggdb $(LFLAGS)
+$(EXEC)_release:	LFLAGS := $(LFLAGS)
+$(EXEC)_static:		LFLAGS := --static $(LFLAGS)
+
+## Dependencies
+$(EXEC):		$(COBJS)
+$(EXEC)_profile:	$(PCOBJS)
+$(EXEC)_debug:		$(DCOBJS)
+$(EXEC)_release:	$(RCOBJS)
+$(EXEC)_static:		$(RCOBJS)
+
+lib$(LIB).a:	$(filter-out Main.or, $(RCOBJS))
+lib$(LIB)d.a:	$(filter-out Main.od, $(DCOBJS))
+
+
+## Build rule
+%.o %.op %.od %.or:	%.C
+	@echo Compiling: "$@ ( $< )"
+	@$(CXX) $(CFLAGS) -c -o $@ $<
+
+## Linking rules (standard/profile/debug/release)
+$(EXEC) $(EXEC)_profile $(EXEC)_debug $(EXEC)_release $(EXEC)_static:
+	@echo Linking: "$@ ( $^ )"
+	@$(CXX) $^ $(LFLAGS) -o $@
+
+## Library rule
+lib$(LIB).a lib$(LIB)d.a:
+	@echo Library: "$@ ( $^ )"
+	@rm -f $@
+	@ar cq $@ $^
+
+## Clean rule
+clean:
+	@rm -f $(EXEC) $(EXEC)_profile $(EXEC)_debug $(EXEC)_release $(EXEC)_static \
+	  $(COBJS) $(PCOBJS) $(DCOBJS) $(RCOBJS) *.core depend.mak lib$(LIB).a lib$(LIB)d.a
+
+## Make dependencies
+depend.mk: $(CSRCS) $(CHDRS)
+	@echo Making dependencies ...
+	@$(CXX) $(CFLAGS) -MM $(CSRCS) > depend.mk
+	@cp depend.mk /tmp/depend.mk.tmp
+	@sed "s/o:/op:/" /tmp/depend.mk.tmp >> depend.mk
+	@sed "s/o:/od:/" /tmp/depend.mk.tmp >> depend.mk
+	@sed "s/o:/or:/" /tmp/depend.mk.tmp >> depend.mk
+	@rm /tmp/depend.mk.tmp
+
+-include depend.mk
diff --git a/src/prop/minisat/simp/Main.C b/src/prop/minisat/simp/Main.C
new file mode 100644
index 000000000..b6d194631
--- /dev/null
+++ b/src/prop/minisat/simp/Main.C
@@ -0,0 +1,415 @@
+/******************************************************************************************[Main.C]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#include <ctime>
+#include <cstring>
+#include <stdint.h>
+#include <errno.h>
+
+#include <signal.h>
+#include <zlib.h>
+
+#include "SimpSolver.h"
+
+/*************************************************************************************/
+#ifdef _MSC_VER
+#include <ctime>
+
+static inline double cpuTime(void) {
+    return (double)clock() / CLOCKS_PER_SEC; }
+#else
+
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <unistd.h>
+
+static inline double cpuTime(void) {
+    struct rusage ru;
+    getrusage(RUSAGE_SELF, &ru);
+    return (double)ru.ru_utime.tv_sec + (double)ru.ru_utime.tv_usec / 1000000; }
+#endif
+
+
+#if defined(__linux__)
+static inline int memReadStat(int field)
+{
+    char    name[256];
+    pid_t pid = getpid();
+    sprintf(name, "/proc/%d/statm", pid);
+    FILE*   in = fopen(name, "rb");
+    if (in == NULL) return 0;
+    int     value;
+    for (; field >= 0; field--)
+        fscanf(in, "%d", &value);
+    fclose(in);
+    return value;
+}
+static inline uint64_t memUsed() { return (uint64_t)memReadStat(0) * (uint64_t)getpagesize(); }
+
+
+#elif defined(__FreeBSD__)
+static inline uint64_t memUsed(void) {
+    struct rusage ru;
+    getrusage(RUSAGE_SELF, &ru);
+    return ru.ru_maxrss*1024; }
+
+
+#else
+static inline uint64_t memUsed() { return 0; }
+#endif
+
+#if defined(__linux__)
+#include <fpu_control.h>
+#endif
+
+
+//=================================================================================================
+// DIMACS Parser:
+
+#define CHUNK_LIMIT 1048576
+
+class StreamBuffer {
+    gzFile  in;
+    char    buf[CHUNK_LIMIT];
+    int     pos;
+    int     size;
+
+    void assureLookahead() {
+        if (pos >= size) {
+            pos  = 0;
+            size = gzread(in, buf, sizeof(buf)); } }
+
+public:
+    StreamBuffer(gzFile i) : in(i), pos(0), size(0) {
+        assureLookahead(); }
+
+    int  operator *  () { return (pos >= size) ? EOF : buf[pos]; }
+    void operator ++ () { pos++; assureLookahead(); }
+};
+
+//- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+template<class B>
+static void skipWhitespace(B& in) {
+    while ((*in >= 9 && *in <= 13) || *in == 32)
+        ++in; }
+
+template<class B>
+static void skipLine(B& in) {
+    for (;;){
+        if (*in == EOF || *in == '\0') return;
+        if (*in == '\n') { ++in; return; }
+        ++in; } }
+
+template<class B>
+static int parseInt(B& in) {
+    int     val = 0;
+    bool    neg = false;
+    skipWhitespace(in);
+    if      (*in == '-') neg = true, ++in;
+    else if (*in == '+') ++in;
+    if (*in < '0' || *in > '9') reportf("PARSE ERROR! Unexpected char: %c\n", *in), exit(3);
+    while (*in >= '0' && *in <= '9')
+        val = val*10 + (*in - '0'),
+        ++in;
+    return neg ? -val : val; }
+
+template<class B>
+static void readClause(B& in, SimpSolver& S, vec<Lit>& lits) {
+    int     parsed_lit, var;
+    lits.clear();
+    for (;;){
+        parsed_lit = parseInt(in);
+        if (parsed_lit == 0) break;
+        var = abs(parsed_lit)-1;
+        while (var >= S.nVars()) S.newVar();
+        lits.push( (parsed_lit > 0) ? Lit(var) : ~Lit(var) );
+    }
+}
+
+template<class B>
+static bool match(B& in, char* str) {
+    for (; *str != 0; ++str, ++in)
+        if (*str != *in)
+            return false;
+    return true;
+}
+
+
+template<class B>
+static void parse_DIMACS_main(B& in, SimpSolver& S) {
+    vec<Lit> lits;
+    for (;;){
+        skipWhitespace(in);
+        if (*in == EOF) break;
+        else if (*in == 'p'){
+            if (match(in, "p cnf")){
+                int vars    = parseInt(in);
+                int clauses = parseInt(in);
+                reportf("|  Number of variables:  %-12d                                         |\n", vars);
+                reportf("|  Number of clauses:    %-12d                                         |\n", clauses);
+
+                // SATRACE'06 hack
+                if (clauses > 4000000)
+                    S.eliminate(true);
+            }else{
+                reportf("PARSE ERROR! Unexpected char: %c\n", *in), exit(3);
+            }
+        } else if (*in == 'c' || *in == 'p')
+            skipLine(in);
+        else{
+            readClause(in, S, lits);
+            S.addClause(lits); }
+    }
+}
+
+// Inserts problem into solver.
+//
+static void parse_DIMACS(gzFile input_stream, SimpSolver& S) {
+    StreamBuffer in(input_stream);
+    parse_DIMACS_main(in, S); }
+
+
+//=================================================================================================
+
+
+void printStats(Solver& S)
+{
+    double   cpu_time = cpuTime();
+    uint64_t mem_used = memUsed();
+    reportf("restarts              : %lld\n", S.starts);
+    reportf("conflicts             : %-12lld   (%.0f /sec)\n", S.conflicts   , S.conflicts   /cpu_time);
+    reportf("decisions             : %-12lld   (%4.2f %% random) (%.0f /sec)\n", S.decisions, (float)S.rnd_decisions*100 / (float)S.decisions, S.decisions   /cpu_time);
+    reportf("propagations          : %-12lld   (%.0f /sec)\n", S.propagations, S.propagations/cpu_time);
+    reportf("conflict literals     : %-12lld   (%4.2f %% deleted)\n", S.tot_literals, (S.max_literals - S.tot_literals)*100 / (double)S.max_literals);
+    if (mem_used != 0) reportf("Memory used           : %.2f MB\n", mem_used / 1048576.0);
+    reportf("CPU time              : %g s\n", cpu_time);
+}
+
+SimpSolver* solver;
+static void SIGINT_handler(int signum) {
+    reportf("\n"); reportf("*** INTERRUPTED ***\n");
+    printStats(*solver);
+    reportf("\n"); reportf("*** INTERRUPTED ***\n");
+    exit(1); }
+
+
+//=================================================================================================
+// Main:
+
+void printUsage(char** argv)
+{
+    reportf("USAGE: %s [options] <input-file> <result-output-file>\n\n  where input may be either in plain or gzipped DIMACS.\n\n", argv[0]);
+    reportf("OPTIONS:\n\n");
+    reportf("  -pre           = {none,once}\n");
+    reportf("  -asymm\n");
+    reportf("  -rcheck\n");
+    reportf("  -grow          = <num> [ >0 ]\n");
+    reportf("  -polarity-mode = {true,false,rnd}\n");
+    reportf("  -decay         = <num> [ 0 - 1 ]\n");
+    reportf("  -rnd-freq      = <num> [ 0 - 1 ]\n");
+    reportf("  -dimacs        = <output-file>\n");
+    reportf("  -verbosity     = {0,1,2}\n");
+    reportf("\n");
+}
+
+typedef enum { pre_none, pre_once, pre_repeat } preprocessMode;
+
+const char* hasPrefix(const char* str, const char* prefix)
+{
+    int len = strlen(prefix);
+    if (strncmp(str, prefix, len) == 0)
+        return str + len;
+    else
+        return NULL;
+}
+
+
+int main(int argc, char** argv)
+{
+    reportf("This is MiniSat 2.0 beta\n");
+#if defined(__linux__)
+    fpu_control_t oldcw, newcw;
+    _FPU_GETCW(oldcw); newcw = (oldcw & ~_FPU_EXTENDED) | _FPU_DOUBLE; _FPU_SETCW(newcw);
+    reportf("WARNING: for repeatability, setting FPU to use double precision\n");
+#endif
+    preprocessMode pre    = pre_once;
+    const char*    dimacs = NULL;
+    const char*    freeze = NULL;
+    SimpSolver     S;
+    S.verbosity = 1;
+
+    // This just grew and grew, and I didn't have time to do sensible argument parsing yet :)
+    //
+    int         i, j;
+    const char* value;
+    for (i = j = 0; i < argc; i++){
+        if ((value = hasPrefix(argv[i], "-polarity-mode="))){
+            if (strcmp(value, "true") == 0)
+                S.polarity_mode = Solver::polarity_true;
+            else if (strcmp(value, "false") == 0)
+                S.polarity_mode = Solver::polarity_false;
+            else if (strcmp(value, "rnd") == 0)
+                S.polarity_mode = Solver::polarity_rnd;
+            else{
+                reportf("ERROR! unknown polarity-mode %s\n", value);
+                exit(0); }
+
+        }else if ((value = hasPrefix(argv[i], "-rnd-freq="))){
+            double rnd;
+            if (sscanf(value, "%lf", &rnd) <= 0 || rnd < 0 || rnd > 1){
+                reportf("ERROR! illegal rnd-freq constant %s\n", value);
+                exit(0); }
+            S.random_var_freq = rnd;
+
+        }else if ((value = hasPrefix(argv[i], "-decay="))){
+            double decay;
+            if (sscanf(value, "%lf", &decay) <= 0 || decay <= 0 || decay > 1){
+                reportf("ERROR! illegal decay constant %s\n", value);
+                exit(0); }
+            S.var_decay = 1 / decay;
+
+        }else if ((value = hasPrefix(argv[i], "-verbosity="))){
+            int verbosity = (int)strtol(value, NULL, 10);
+            if (verbosity == 0 && errno == EINVAL){
+                reportf("ERROR! illegal verbosity level %s\n", value);
+                exit(0); }
+            S.verbosity = verbosity;
+
+        }else if ((value = hasPrefix(argv[i], "-pre="))){
+            if (strcmp(value, "none") == 0)
+                pre = pre_none;
+            else if (strcmp(value, "once") == 0)
+                pre = pre_once;
+            else if (strcmp(value, "repeat") == 0){
+                pre = pre_repeat;
+                reportf("ERROR! preprocessing mode \"repeat\" is not supported at the moment.\n");
+                exit(0);
+            }else{
+                reportf("ERROR! unknown preprocessing mode %s\n", value);
+                exit(0); }
+        }else if (strcmp(argv[i], "-asymm") == 0){
+            S.asymm_mode = true;
+        }else if (strcmp(argv[i], "-rcheck") == 0){
+            S.redundancy_check = true;
+        }else if ((value = hasPrefix(argv[i], "-grow="))){
+            int grow = (int)strtol(value, NULL, 10);
+            if (grow == 0 && errno == EINVAL){
+                reportf("ERROR! illegal grow constant %s\n", &argv[i][6]);
+                exit(0); }
+            S.grow = grow;
+        }else if ((value = hasPrefix(argv[i], "-dimacs="))){
+            dimacs = value;
+        }else if ((value = hasPrefix(argv[i], "-freeze="))){
+            freeze = value;
+        }else if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "-help") == 0){
+            printUsage(argv);
+            exit(0);
+        }else if (strncmp(argv[i], "-", 1) == 0){
+            reportf("ERROR! unknown flag %s\n", argv[i]);
+            exit(0);
+        }else
+            argv[j++] = argv[i];
+    }
+    argc = j;
+
+    double cpu_time = cpuTime();
+
+    if (pre == pre_none)
+        S.eliminate(true);
+
+    solver = &S;
+    signal(SIGINT,SIGINT_handler);
+    signal(SIGHUP,SIGINT_handler);
+
+    if (argc == 1)
+        reportf("Reading from standard input... Use '-h' or '--help' for help.\n");
+
+    gzFile in = (argc == 1) ? gzdopen(0, "rb") : gzopen(argv[1], "rb");
+    if (in == NULL)
+        reportf("ERROR! Could not open file: %s\n", argc == 1 ? "<stdin>" : argv[1]), exit(1);
+
+    reportf("============================[ Problem Statistics ]=============================\n");
+    reportf("|                                                                             |\n");
+
+    parse_DIMACS(in, S);
+    gzclose(in);
+    FILE* res = (argc >= 3) ? fopen(argv[2], "wb") : NULL;
+
+
+    double parse_time = cpuTime() - cpu_time;
+    reportf("|  Parsing time:         %-12.2f s                                       |\n", parse_time);
+
+    /*HACK: Freeze variables*/
+    if (freeze != NULL && pre != pre_none){
+        int   count = 0;
+        FILE* in = fopen(freeze, "rb");
+        for(;;){
+            Var x;
+            fscanf(in, "%d", &x);
+            if (x == 0) break;
+            x--;
+
+            /**/assert(S.n_occ[toInt(Lit(x))] + S.n_occ[toInt(~Lit(x))] != 0);
+            /**/assert(S.value(x) == l_Undef);
+            S.setFrozen(x, true);
+            count++;
+        }
+        fclose(in);
+        reportf("|  Frozen vars :         %-12.0f                                         |\n", (double)count);
+    }
+    /*END*/
+
+    if (!S.simplify()){
+        reportf("Solved by unit propagation\n");
+        if (res != NULL) fprintf(res, "UNSAT\n"), fclose(res);
+        printf("UNSATISFIABLE\n");
+        exit(20);
+    }
+
+    if (dimacs){
+        if (pre != pre_none)
+            S.eliminate(true);
+        reportf("==============================[ Writing DIMACS ]===============================\n");
+        S.toDimacs(dimacs);
+        printStats(S);
+        exit(0);
+    }else{
+        bool ret = S.solve(true, true);
+        printStats(S);
+        reportf("\n");
+
+        printf(ret ? "SATISFIABLE\n" : "UNSATISFIABLE\n");
+        if (res != NULL){
+            if (ret){
+                fprintf(res, "SAT\n");
+                for (int i = 0; i < S.nVars(); i++)
+                    if (S.model[i] != l_Undef)
+                        fprintf(res, "%s%s%d", (i==0)?"":" ", (S.model[i]==l_True)?"":"-", i+1);
+                fprintf(res, " 0\n");
+            }else
+                fprintf(res, "UNSAT\n");
+            fclose(res);
+        }
+#ifdef NDEBUG
+        exit(ret ? 10 : 20);     // (faster than "return", which will invoke the destructor for 'Solver')
+#endif
+    }
+
+}
diff --git a/src/prop/minisat/simp/Makefile b/src/prop/minisat/simp/Makefile
new file mode 100644
index 000000000..a1db4951b
--- /dev/null
+++ b/src/prop/minisat/simp/Makefile
@@ -0,0 +1,11 @@
+MTL       = ../mtl
+CORE      = ../core
+CHDRS     = $(wildcard *.h) $(wildcard $(MTL)/*.h)
+EXEC      = minisat
+CFLAGS    = -I$(MTL) -I$(CORE) -Wall -ffloat-store
+LFLAGS    = -lz
+
+CSRCS     = $(wildcard *.C)
+COBJS     = $(addsuffix .o, $(basename $(CSRCS))) $(CORE)/Solver.o
+
+include ../mtl/template.mk
diff --git a/src/prop/minisat/simp/SimpSolver.C b/src/prop/minisat/simp/SimpSolver.C
new file mode 100644
index 000000000..22121c31e
--- /dev/null
+++ b/src/prop/minisat/simp/SimpSolver.C
@@ -0,0 +1,700 @@
+/************************************************************************************[SimpSolver.C]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#include "Sort.h"
+#include "SimpSolver.h"
+
+
+//=================================================================================================
+// Constructor/Destructor:
+
+
+SimpSolver::SimpSolver() :
+    grow               (0)
+  , asymm_mode         (false)
+  , redundancy_check   (false)
+  , merges             (0)
+  , asymm_lits         (0)
+  , remembered_clauses (0)
+  , elimorder          (1)
+  , use_simplification (true)
+  , elim_heap          (ElimLt(n_occ))
+  , bwdsub_assigns     (0)
+{
+    vec<Lit> dummy(1,lit_Undef);
+    bwdsub_tmpunit   = Clause_new(dummy);
+    remove_satisfied = false;
+}
+
+
+SimpSolver::~SimpSolver()
+{
+    free(bwdsub_tmpunit);
+
+    // NOTE: elimtable.size() might be lower than nVars() at the moment
+    for (int i = 0; i < elimtable.size(); i++)
+        for (int j = 0; j < elimtable[i].eliminated.size(); j++)
+            free(elimtable[i].eliminated[j]);
+}
+
+
+Var SimpSolver::newVar(bool sign, bool dvar) {
+    Var v = Solver::newVar(sign, dvar);
+
+    if (use_simplification){
+        n_occ    .push(0);
+        n_occ    .push(0);
+        occurs   .push();
+        frozen   .push((char)false);
+        touched  .push(0);
+        elim_heap.insert(v);
+        elimtable.push();
+    }
+    return v; }
+
+
+
+bool SimpSolver::solve(const vec<Lit>& assumps, bool do_simp, bool turn_off_simp) {
+    vec<Var> extra_frozen;
+    bool     result = true;
+
+    do_simp &= use_simplification;
+
+    if (do_simp){
+        // Assumptions must be temporarily frozen to run variable elimination:
+        for (int i = 0; i < assumps.size(); i++){
+            Var v = var(assumps[i]);
+
+            // If an assumption has been eliminated, remember it.
+            if (isEliminated(v))
+                remember(v);
+
+            if (!frozen[v]){
+                // Freeze and store.
+                setFrozen(v, true);
+                extra_frozen.push(v);
+            } }
+
+        result = eliminate(turn_off_simp);
+    }
+
+    if (result)
+        result = Solver::solve(assumps);
+
+    if (result) {
+        extendModel();
+#ifndef NDEBUG
+        verifyModel();
+#endif
+    }
+
+    if (do_simp)
+        // Unfreeze the assumptions that were frozen:
+        for (int i = 0; i < extra_frozen.size(); i++)
+            setFrozen(extra_frozen[i], false);
+
+    return result;
+}
+
+
+
+bool SimpSolver::addClause(vec<Lit>& ps)
+{
+    for (int i = 0; i < ps.size(); i++)
+        if (isEliminated(var(ps[i])))
+            remember(var(ps[i]));
+
+    int nclauses = clauses.size();
+
+    if (redundancy_check && implied(ps))
+        return true;
+
+    if (!Solver::addClause(ps))
+        return false;
+
+    if (use_simplification && clauses.size() == nclauses + 1){
+        Clause& c = *clauses.last();
+
+        subsumption_queue.insert(&c);
+
+        for (int i = 0; i < c.size(); i++){
+            assert(occurs.size() > var(c[i]));
+            assert(!find(occurs[var(c[i])], &c));
+
+            occurs[var(c[i])].push(&c);
+            n_occ[toInt(c[i])]++;
+            touched[var(c[i])] = 1;
+            assert(elimtable[var(c[i])].order == 0);
+            if (elim_heap.inHeap(var(c[i])))
+                elim_heap.increase_(var(c[i]));
+        }
+    }
+
+    return true;
+}
+
+
+void SimpSolver::removeClause(Clause& c)
+{
+    assert(!c.learnt());
+
+    if (use_simplification)
+        for (int i = 0; i < c.size(); i++){
+            n_occ[toInt(c[i])]--;
+            updateElimHeap(var(c[i]));
+        }
+
+    detachClause(c);
+    c.mark(1);
+}
+
+
+bool SimpSolver::strengthenClause(Clause& c, Lit l)
+{
+    assert(decisionLevel() == 0);
+    assert(c.mark() == 0);
+    assert(!c.learnt());
+    assert(find(watches[toInt(~c[0])], &c));
+    assert(find(watches[toInt(~c[1])], &c));
+
+    // FIX: this is too inefficient but would be nice to have (properly implemented)
+    // if (!find(subsumption_queue, &c))
+    subsumption_queue.insert(&c);
+
+    // If l is watched, delete it from watcher list and watch a new literal
+    if (c[0] == l || c[1] == l){
+        Lit other = c[0] == l ? c[1] : c[0];
+        if (c.size() == 2){
+            removeClause(c);
+            c.strengthen(l);
+        }else{
+            c.strengthen(l);
+            remove(watches[toInt(~l)], &c);
+
+            // Add a watch for the correct literal
+            watches[toInt(~(c[1] == other ? c[0] : c[1]))].push(&c);
+
+            // !! this version assumes that remove does not change the order !!
+            //watches[toInt(~c[1])].push(&c);
+            clauses_literals -= 1;
+        }
+    }
+    else{
+        c.strengthen(l);
+        clauses_literals -= 1;
+    }
+
+    // if subsumption-indexing is active perform the necessary updates
+    if (use_simplification){
+        remove(occurs[var(l)], &c);
+        n_occ[toInt(l)]--;
+        updateElimHeap(var(l));
+    }
+
+    return c.size() == 1 ? enqueue(c[0]) && propagate() == NULL : true;
+}
+
+
+// Returns FALSE if clause is always satisfied ('out_clause' should not be used).
+bool SimpSolver::merge(const Clause& _ps, const Clause& _qs, Var v, vec<Lit>& out_clause)
+{
+    merges++;
+    out_clause.clear();
+
+    bool  ps_smallest = _ps.size() < _qs.size();
+    const Clause& ps =  ps_smallest ? _qs : _ps;
+    const Clause& qs =  ps_smallest ? _ps : _qs;
+
+    for (int i = 0; i < qs.size(); i++){
+        if (var(qs[i]) != v){
+            for (int j = 0; j < ps.size(); j++)
+                if (var(ps[j]) == var(qs[i]))
+                    if (ps[j] == ~qs[i])
+                        return false;
+                    else
+                        goto next;
+            out_clause.push(qs[i]);
+        }
+        next:;
+    }
+
+    for (int i = 0; i < ps.size(); i++)
+        if (var(ps[i]) != v)
+            out_clause.push(ps[i]);
+
+    return true;
+}
+
+
+// Returns FALSE if clause is always satisfied.
+bool SimpSolver::merge(const Clause& _ps, const Clause& _qs, Var v)
+{
+    merges++;
+
+    bool  ps_smallest = _ps.size() < _qs.size();
+    const Clause& ps =  ps_smallest ? _qs : _ps;
+    const Clause& qs =  ps_smallest ? _ps : _qs;
+    const Lit* __ps = (const Lit*)ps;
+    const Lit* __qs = (const Lit*)qs;
+
+    for (int i = 0; i < qs.size(); i++){
+        if (var(__qs[i]) != v){
+            for (int j = 0; j < ps.size(); j++)
+                if (var(__ps[j]) == var(__qs[i]))
+                    if (__ps[j] == ~__qs[i])
+                        return false;
+                    else
+                        goto next;
+        }
+        next:;
+    }
+
+    return true;
+}
+
+
+void SimpSolver::gatherTouchedClauses()
+{
+    //fprintf(stderr, "Gathering clauses for backwards subsumption\n");
+    int ntouched = 0;
+    for (int i = 0; i < touched.size(); i++)
+        if (touched[i]){
+            const vec<Clause*>& cs = getOccurs(i);
+            ntouched++;
+            for (int j = 0; j < cs.size(); j++)
+                if (cs[j]->mark() == 0){
+                    subsumption_queue.insert(cs[j]);
+                    cs[j]->mark(2);
+                }
+            touched[i] = 0;
+        }
+
+    //fprintf(stderr, "Touched variables %d of %d yields %d clauses to check\n", ntouched, touched.size(), clauses.size());
+    for (int i = 0; i < subsumption_queue.size(); i++)
+        subsumption_queue[i]->mark(0);
+}
+
+
+bool SimpSolver::implied(const vec<Lit>& c)
+{
+    assert(decisionLevel() == 0);
+
+    trail_lim.push(trail.size());
+    for (int i = 0; i < c.size(); i++)
+        if (value(c[i]) == l_True){
+            cancelUntil(0);
+            return false;
+        }else if (value(c[i]) != l_False){
+            assert(value(c[i]) == l_Undef);
+            uncheckedEnqueue(~c[i]);
+        }
+
+    bool result = propagate() != NULL;
+    cancelUntil(0);
+    return result;
+}
+
+
+// Backward subsumption + backward subsumption resolution
+bool SimpSolver::backwardSubsumptionCheck(bool verbose)
+{
+    int cnt = 0;
+    int subsumed = 0;
+    int deleted_literals = 0;
+    assert(decisionLevel() == 0);
+
+    while (subsumption_queue.size() > 0 || bwdsub_assigns < trail.size()){
+
+        // Check top-level assignments by creating a dummy clause and placing it in the queue:
+        if (subsumption_queue.size() == 0 && bwdsub_assigns < trail.size()){
+            Lit l = trail[bwdsub_assigns++];
+            (*bwdsub_tmpunit)[0] = l;
+            bwdsub_tmpunit->calcAbstraction();
+            assert(bwdsub_tmpunit->mark() == 0);
+            subsumption_queue.insert(bwdsub_tmpunit); }
+
+        Clause&  c = *subsumption_queue.peek(); subsumption_queue.pop();
+
+        if (c.mark()) continue;
+
+        if (verbose && verbosity >= 2 && cnt++ % 1000 == 0)
+            reportf("subsumption left: %10d (%10d subsumed, %10d deleted literals)\r", subsumption_queue.size(), subsumed, deleted_literals);
+
+        assert(c.size() > 1 || value(c[0]) == l_True);    // Unit-clauses should have been propagated before this point.
+
+        // Find best variable to scan:
+        Var best = var(c[0]);
+        for (int i = 1; i < c.size(); i++)
+            if (occurs[var(c[i])].size() < occurs[best].size())
+                best = var(c[i]);
+
+        // Search all candidates:
+        vec<Clause*>& _cs = getOccurs(best);
+        Clause**       cs = (Clause**)_cs;
+
+        for (int j = 0; j < _cs.size(); j++)
+            if (c.mark())
+                break;
+            else if (!cs[j]->mark() && cs[j] != &c){
+                Lit l = c.subsumes(*cs[j]);
+
+                if (l == lit_Undef)
+                    subsumed++, removeClause(*cs[j]);
+                else if (l != lit_Error){
+                    deleted_literals++;
+
+                    if (!strengthenClause(*cs[j], ~l))
+                        return false;
+
+                    // Did current candidate get deleted from cs? Then check candidate at index j again:
+                    if (var(l) == best)
+                        j--;
+                }
+            }
+    }
+
+    return true;
+}
+
+
+bool SimpSolver::asymm(Var v, Clause& c)
+{
+    assert(decisionLevel() == 0);
+
+    if (c.mark() || satisfied(c)) return true;
+
+    trail_lim.push(trail.size());
+    Lit l = lit_Undef;
+    for (int i = 0; i < c.size(); i++)
+        if (var(c[i]) != v && value(c[i]) != l_False)
+            uncheckedEnqueue(~c[i]);
+        else
+            l = c[i];
+
+    if (propagate() != NULL){
+        cancelUntil(0);
+        asymm_lits++;
+        if (!strengthenClause(c, l))
+            return false;
+    }else
+        cancelUntil(0);
+
+    return true;
+}
+
+
+bool SimpSolver::asymmVar(Var v)
+{
+    assert(!frozen[v]);
+    assert(use_simplification);
+
+    vec<Clause*>  pos, neg;
+    const vec<Clause*>& cls = getOccurs(v);
+
+    if (value(v) != l_Undef || cls.size() == 0)
+        return true;
+
+    for (int i = 0; i < cls.size(); i++)
+        if (!asymm(v, *cls[i]))
+            return false;
+
+    return backwardSubsumptionCheck();
+}
+
+
+void SimpSolver::verifyModel()
+{
+    bool failed = false;
+    int  cnt    = 0;
+    // NOTE: elimtable.size() might be lower than nVars() at the moment
+    for (int i = 0; i < elimtable.size(); i++)
+        if (elimtable[i].order > 0)
+            for (int j = 0; j < elimtable[i].eliminated.size(); j++){
+                cnt++;
+                Clause& c = *elimtable[i].eliminated[j];
+                for (int k = 0; k < c.size(); k++)
+                    if (modelValue(c[k]) == l_True)
+                        goto next;
+
+                reportf("unsatisfied clause: ");
+                printClause(*elimtable[i].eliminated[j]);
+                reportf("\n");
+                failed = true;
+            next:;
+            }
+
+    assert(!failed);
+    reportf("Verified %d eliminated clauses.\n", cnt);
+}
+
+
+bool SimpSolver::eliminateVar(Var v, bool fail)
+{
+    if (!fail && asymm_mode && !asymmVar(v))    return false;
+
+    const vec<Clause*>& cls = getOccurs(v);
+
+//  if (value(v) != l_Undef || cls.size() == 0) return true;
+    if (value(v) != l_Undef) return true;
+
+    // Split the occurrences into positive and negative:
+    vec<Clause*>  pos, neg;
+    for (int i = 0; i < cls.size(); i++)
+        (find(*cls[i], Lit(v)) ? pos : neg).push(cls[i]);
+
+    // Check if number of clauses decreases:
+    int cnt = 0;
+    for (int i = 0; i < pos.size(); i++)
+        for (int j = 0; j < neg.size(); j++)
+            if (merge(*pos[i], *neg[j], v) && ++cnt > cls.size() + grow)
+                return true;
+
+    // Delete and store old clauses:
+    setDecisionVar(v, false);
+    elimtable[v].order = elimorder++;
+    assert(elimtable[v].eliminated.size() == 0);
+    for (int i = 0; i < cls.size(); i++){
+        elimtable[v].eliminated.push(Clause_new(*cls[i]));
+        removeClause(*cls[i]); }
+
+    // Produce clauses in cross product:
+    int top = clauses.size();
+    vec<Lit> resolvent;
+    for (int i = 0; i < pos.size(); i++)
+        for (int j = 0; j < neg.size(); j++)
+            if (merge(*pos[i], *neg[j], v, resolvent) && !addClause(resolvent))
+                return false;
+
+    // DEBUG: For checking that a clause set is saturated with respect to variable elimination.
+    //        If the clause set is expected to be saturated at this point, this constitutes an
+    //        error.
+    if (fail){
+        reportf("eliminated var %d, %d <= %d\n", v+1, cnt, cls.size());
+        reportf("previous clauses:\n");
+        for (int i = 0; i < cls.size(); i++){
+            printClause(*cls[i]); reportf("\n"); }
+        reportf("new clauses:\n");
+        for (int i = top; i < clauses.size(); i++){
+            printClause(*clauses[i]); reportf("\n"); }
+        assert(0); }
+
+    return backwardSubsumptionCheck();
+}
+
+
+void SimpSolver::remember(Var v)
+{
+    assert(decisionLevel() == 0);
+    assert(isEliminated(v));
+
+    vec<Lit> clause;
+
+    // Re-activate variable:
+    elimtable[v].order = 0;
+    setDecisionVar(v, true); // Not good if the variable wasn't a decision variable before. Not sure how to fix this right now.
+
+    if (use_simplification)
+        updateElimHeap(v);
+
+    // Reintroduce all old clauses which may implicitly remember other clauses:
+    for (int i = 0; i < elimtable[v].eliminated.size(); i++){
+        Clause& c = *elimtable[v].eliminated[i];
+        clause.clear();
+        for (int j = 0; j < c.size(); j++)
+            clause.push(c[j]);
+
+        remembered_clauses++;
+        check(addClause(clause));
+        free(&c);
+    }
+
+    elimtable[v].eliminated.clear();
+}
+
+
+void SimpSolver::extendModel()
+{
+    vec<Var> vs;
+
+    // NOTE: elimtable.size() might be lower than nVars() at the moment
+    for (int v = 0; v < elimtable.size(); v++)
+        if (elimtable[v].order > 0)
+            vs.push(v);
+
+    sort(vs, ElimOrderLt(elimtable));
+
+    for (int i = 0; i < vs.size(); i++){
+        Var v = vs[i];
+        Lit l = lit_Undef;
+
+        for (int j = 0; j < elimtable[v].eliminated.size(); j++){
+            Clause& c = *elimtable[v].eliminated[j];
+
+            for (int k = 0; k < c.size(); k++)
+                if (var(c[k]) == v)
+                    l = c[k];
+                else if (modelValue(c[k]) != l_False)
+                    goto next;
+
+            assert(l != lit_Undef);
+            model[v] = lbool(!sign(l));
+            break;
+
+        next:;
+        }
+
+        if (model[v] == l_Undef)
+            model[v] = l_True;
+    }
+}
+
+
+bool SimpSolver::eliminate(bool turn_off_elim)
+{
+    if (!ok || !use_simplification)
+        return ok;
+
+    // Main simplification loop:
+    //assert(subsumption_queue.size() == 0);
+    //gatherTouchedClauses();
+    while (subsumption_queue.size() > 0 || elim_heap.size() > 0){
+
+        //fprintf(stderr, "subsumption phase: (%d)\n", subsumption_queue.size());
+        if (!backwardSubsumptionCheck(true))
+            return false;
+
+        //fprintf(stderr, "elimination phase:\n (%d)", elim_heap.size());
+        for (int cnt = 0; !elim_heap.empty(); cnt++){
+            Var elim = elim_heap.removeMin();
+
+            if (verbosity >= 2 && cnt % 100 == 0)
+                reportf("elimination left: %10d\r", elim_heap.size());
+
+            if (!frozen[elim] && !eliminateVar(elim))
+                return false;
+        }
+
+        assert(subsumption_queue.size() == 0);
+        gatherTouchedClauses();
+    }
+
+    // Cleanup:
+    cleanUpClauses();
+    order_heap.filter(VarFilter(*this));
+
+#ifdef INVARIANTS
+    // Check that no more subsumption is possible:
+    reportf("Checking that no more subsumption is possible\n");
+    for (int i = 0; i < clauses.size(); i++){
+        if (i % 1000 == 0)
+            reportf("left %10d\r", clauses.size() - i);
+
+        assert(clauses[i]->mark() == 0);
+        for (int j = 0; j < i; j++)
+            assert(clauses[i]->subsumes(*clauses[j]) == lit_Error);
+    }
+    reportf("done.\n");
+
+    // Check that no more elimination is possible:
+    reportf("Checking that no more elimination is possible\n");
+    for (int i = 0; i < nVars(); i++)
+        if (!frozen[i]) eliminateVar(i, true);
+    reportf("done.\n");
+    checkLiteralCount();
+#endif
+
+    // If no more simplification is needed, free all simplification-related data structures:
+    if (turn_off_elim){
+        use_simplification = false;
+        touched.clear(true);
+        occurs.clear(true);
+        n_occ.clear(true);
+        subsumption_queue.clear(true);
+        elim_heap.clear(true);
+        remove_satisfied = true;
+    }
+
+
+    return true;
+}
+
+
+void SimpSolver::cleanUpClauses()
+{
+    int      i , j;
+    vec<Var> dirty;
+    for (i = 0; i < clauses.size(); i++)
+        if (clauses[i]->mark() == 1){
+            Clause& c = *clauses[i];
+            for (int k = 0; k < c.size(); k++)
+                if (!seen[var(c[k])]){
+                    seen[var(c[k])] = 1;
+                    dirty.push(var(c[k]));
+                } }
+
+    for (i = 0; i < dirty.size(); i++){
+        cleanOcc(dirty[i]);
+        seen[dirty[i]] = 0; }
+
+    for (i = j = 0; i < clauses.size(); i++)
+        if (clauses[i]->mark() == 1)
+            free(clauses[i]);
+        else
+            clauses[j++] = clauses[i];
+    clauses.shrink(i - j);
+}
+
+
+//=================================================================================================
+// Convert to DIMACS:
+
+
+void SimpSolver::toDimacs(FILE* f, Clause& c)
+{
+    if (satisfied(c)) return;
+
+    for (int i = 0; i < c.size(); i++)
+        if (value(c[i]) != l_False)
+            fprintf(f, "%s%d ", sign(c[i]) ? "-" : "", var(c[i])+1);
+    fprintf(f, "0\n");
+}
+
+
+void SimpSolver::toDimacs(const char* file)
+{
+    assert(decisionLevel() == 0);
+    FILE* f = fopen(file, "wr");
+    if (f != NULL){
+
+        // Cannot use removeClauses here because it is not safe
+        // to deallocate them at this point. Could be improved.
+        int cnt = 0;
+        for (int i = 0; i < clauses.size(); i++)
+            if (!satisfied(*clauses[i]))
+                cnt++;
+
+        fprintf(f, "p cnf %d %d\n", nVars(), cnt);
+
+        for (int i = 0; i < clauses.size(); i++)
+            toDimacs(f, *clauses[i]);
+
+        fprintf(stderr, "Wrote %d clauses...\n", clauses.size());
+    }else
+        fprintf(stderr, "could not open file %s\n", file);
+}
diff --git a/src/prop/minisat/simp/SimpSolver.h b/src/prop/minisat/simp/SimpSolver.h
new file mode 100644
index 000000000..f1bf88240
--- /dev/null
+++ b/src/prop/minisat/simp/SimpSolver.h
@@ -0,0 +1,161 @@
+/************************************************************************************[SimpSolver.h]
+MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction,
+including without limitation the rights to use, copy, modify, merge, publish, distribute,
+sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or
+substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
+OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+**************************************************************************************************/
+
+#ifndef SimpSolver_h
+#define SimpSolver_h
+
+#include <cstdio>
+
+#include "Queue.h"
+#include "Solver.h"
+
+
+class SimpSolver : public Solver {
+ public:
+    // Constructor/Destructor:
+    //
+    SimpSolver();
+    ~SimpSolver();
+
+    // Problem specification:
+    //
+    Var     newVar    (bool polarity = true, bool dvar = true);
+    bool    addClause (vec<Lit>& ps);
+
+    // Variable mode:
+    // 
+    void    setFrozen (Var v, bool b); // If a variable is frozen it will not be eliminated.
+
+    // Solving:
+    //
+    bool    solve     (const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
+    bool    solve     (bool do_simp = true, bool turn_off_simp = false);
+    bool    eliminate (bool turn_off_elim = false);  // Perform variable elimination based simplification. 
+
+    // Generate a (possibly simplified) DIMACS file:
+    //
+    void    toDimacs  (const char* file);
+
+    // Mode of operation:
+    //
+    int     grow;             // Allow a variable elimination step to grow by a number of clauses (default to zero).
+    bool    asymm_mode;       // Shrink clauses by asymmetric branching.
+    bool    redundancy_check; // Check if a clause is already implied. Prett costly, and subsumes subsumptions :)
+
+    // Statistics:
+    //
+    int     merges;
+    int     asymm_lits;
+    int     remembered_clauses;
+
+// protected:
+  public:
+
+    // Helper structures:
+    //
+    struct ElimData {
+        int          order;      // 0 means not eliminated, >0 gives an index in the elimination order
+        vec<Clause*> eliminated;
+        ElimData() : order(0) {} };
+
+    struct ElimOrderLt {
+        const vec<ElimData>& elimtable;
+        ElimOrderLt(const vec<ElimData>& et) : elimtable(et) {}
+        bool operator()(Var x, Var y) { return elimtable[x].order > elimtable[y].order; } };
+
+    struct ElimLt {
+        const vec<int>& n_occ;
+        ElimLt(const vec<int>& no) : n_occ(no) {}
+        int  cost      (Var x)        const { return n_occ[toInt(Lit(x))] * n_occ[toInt(~Lit(x))]; }
+        bool operator()(Var x, Var y) const { return cost(x) < cost(y); } };
+
+
+    // Solver state:
+    //
+    int                 elimorder;
+    bool                use_simplification;
+    vec<ElimData>       elimtable;
+    vec<char>           touched;
+    vec<vec<Clause*> >  occurs;
+    vec<int>            n_occ;
+    Heap<ElimLt>        elim_heap;
+    Queue<Clause*>      subsumption_queue;
+    vec<char>           frozen;
+    int                 bwdsub_assigns;
+
+    // Temporaries:
+    //
+    Clause*             bwdsub_tmpunit;
+
+    // Main internal methods:
+    //
+    bool          asymm                    (Var v, Clause& c);
+    bool          asymmVar                 (Var v);
+    void          updateElimHeap           (Var v);
+    void          cleanOcc                 (Var v);
+    vec<Clause*>& getOccurs                (Var x);
+    void          gatherTouchedClauses     ();
+    bool          merge                    (const Clause& _ps, const Clause& _qs, Var v, vec<Lit>& out_clause);
+    bool          merge                    (const Clause& _ps, const Clause& _qs, Var v);
+    bool          backwardSubsumptionCheck (bool verbose = false);
+    bool          eliminateVar             (Var v, bool fail = false);
+    void          remember                 (Var v);
+    void          extendModel              ();
+    void          verifyModel              ();
+
+    void          removeClause             (Clause& c);
+    bool          strengthenClause         (Clause& c, Lit l);
+    void          cleanUpClauses           ();
+    bool          implied                  (const vec<Lit>& c);
+    void          toDimacs                 (FILE* f, Clause& c);
+    bool          isEliminated             (Var v) const;
+
+};
+
+
+//=================================================================================================
+// Implementation of inline methods:
+
+inline void SimpSolver::updateElimHeap(Var v) {
+    if (elimtable[v].order == 0)
+        elim_heap.update(v); }
+
+inline void SimpSolver::cleanOcc(Var v) {
+    assert(use_simplification);
+    Clause **begin = (Clause**)occurs[v];
+    Clause **end = begin + occurs[v].size();
+    Clause **i, **j;
+    for (i = begin, j = end; i < j; i++)
+        if ((*i)->mark() == 1){
+            *i = *(--j);
+            i--;
+        }
+    //occurs[v].shrink_(end - j);  // This seems slower. Why?!
+    occurs[v].shrink(end - j);
+}
+
+inline vec<Clause*>& SimpSolver::getOccurs(Var x) {
+    cleanOcc(x); return occurs[x]; }
+
+inline bool  SimpSolver::isEliminated (Var v) const { return v < elimtable.size() && elimtable[v].order != 0; }
+inline void  SimpSolver::setFrozen    (Var v, bool b) { frozen[v] = (char)b; if (b) { updateElimHeap(v); } }
+inline bool  SimpSolver::solve        (bool do_simp, bool turn_off_simp) { vec<Lit> tmp; return solve(tmp, do_simp, turn_off_simp); }
+
+//=================================================================================================
+#endif