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/************************************************************************************[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 CVC4_MiniSat_SimpSolver_h
#define CVC4_MiniSat_SimpSolver_h
#include <cstdio>
#include "Queue.h"
#include "Solver.h"
namespace CVC4 {
namespace MiniSat {
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); }
}/* CVC4::MiniSat namespace */
}/* CVC4 namespace */
//=================================================================================================
#endif /* CVC4_MiniSat_SimpSolver_h */
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