Interruption, time-out, and deterministic time-out ("resource-out") features.

Details here: http://goedel.cims.nyu.edu/wiki/Meeting_Minutes_-_October_14,_2011#Resource.2Ftime_limiting_API
This will need more work, but it's a start.

Also implemented TheoryEngine::properPropagation().

Other minor things.

5 files changed, 214 insertions, 20 deletions

diff --git a/src/prop/Makefile.am b/src/prop/Makefile.am
index 30be07d7c..c9442a401 100644
--- a/src/prop/Makefile.am
+++ b/src/prop/Makefile.am
@@ -12,6 +12,7 @@ libprop_la_SOURCES = \
 	prop_engine.h \
 	sat.h \
 	sat.cpp \
+	sat_timer.h \
 	cnf_stream.h \
 	cnf_stream.cpp
 
diff --git a/src/prop/prop_engine.cpp b/src/prop/prop_engine.cpp
index e123db0ed..3d5a27d00 100644
--- a/src/prop/prop_engine.cpp
+++ b/src/prop/prop_engine.cpp
@@ -62,7 +62,12 @@ public:
 PropEngine::PropEngine(TheoryEngine* te, Context* context) :
   d_inCheckSat(false),
   d_theoryEngine(te),
-  d_context(context) {
+  d_context(context),
+  d_satSolver(NULL),
+  d_cnfStream(NULL),
+  d_satTimer(*this),
+  d_interrupted(false) {
+
   Debug("prop") << "Constructing the PropEngine" << endl;
 
   d_satSolver = new SatSolver(this, d_theoryEngine, d_context);
@@ -121,7 +126,7 @@ void PropEngine::printSatisfyingAssignment(){
   }
 }
 
-Result PropEngine::checkSat() {
+Result PropEngine::checkSat(unsigned long& millis, unsigned long& resource) {
   Assert(!d_inCheckSat, "Sat solver in solve()!");
   Debug("prop") << "PropEngine::checkSat()" << endl;
 
@@ -133,22 +138,37 @@ Result PropEngine::checkSat() {
   d_theoryEngine->presolve();
 
   if(Options::current()->preprocessOnly) {
+    millis = resource = 0;
     return Result(Result::SAT_UNKNOWN, Result::REQUIRES_FULL_CHECK);
   }
 
+  // Set the timer
+  d_satTimer.set(millis);
+
+  // Reset the interrupted flag
+  d_interrupted = false;
+
   // Check the problem
-  bool result = d_satSolver->solve();
+  SatLiteralValue result = d_satSolver->solve(resource);
+
+  millis = d_satTimer.elapsed();
 
-  if( result && Debug.isOn("prop") ) {
+  if( result == l_Undef ) {
+    Result::UnknownExplanation why =
+      d_satTimer.expired() ? Result::TIMEOUT :
+        (d_interrupted ? Result::INTERRUPTED : Result::RESOURCEOUT);
+    return Result(Result::SAT_UNKNOWN, why);
+  }
+
+  if( result == l_True && Debug.isOn("prop") ) {
     printSatisfyingAssignment();
   }
 
-  Debug("prop") << "PropEngine::checkSat() => "
-                << (result ? "true" : "false") << endl;
-  if(result && d_theoryEngine->isIncomplete()) {
+  Debug("prop") << "PropEngine::checkSat() => " << result << endl;
+  if(result == l_True && d_theoryEngine->isIncomplete()) {
     return Result(Result::SAT_UNKNOWN, Result::INCOMPLETE);
   }
-  return Result(result ? Result::SAT : Result::UNSAT);
+  return Result(result == l_True ? Result::SAT : Result::UNSAT);
 }
 
 Node PropEngine::getValue(TNode node) {
@@ -170,6 +190,10 @@ bool PropEngine::isSatLiteral(TNode node) {
   return d_cnfStream->hasLiteral(node);
 }
 
+bool PropEngine::isTranslatedSatLiteral(TNode node) {
+  return d_cnfStream->isTranslated(node);
+}
+
 bool PropEngine::hasValue(TNode node, bool& value) {
   Assert(node.getType().isBoolean());
   SatLiteral lit = d_cnfStream->getLiteral(node);
@@ -203,5 +227,20 @@ void PropEngine::pop() {
   Debug("prop") << "pop()" << endl;
 }
 
+void PropEngine::interrupt() throw(ModalException) {
+  if(! d_inCheckSat) {
+    throw ModalException("SAT solver is not currently solving anything; "
+                         "cannot interrupt it");
+  }
+
+  d_interrupted = true;
+  d_satSolver->interrupt();
+  Debug("prop") << "interrupt()" << endl;
+}
+
+void PropEngine::spendResource() throw() {
+  // TODO implement me
+}
+
 }/* CVC4::prop namespace */
 }/* CVC4 namespace */
diff --git a/src/prop/prop_engine.h b/src/prop/prop_engine.h
index 16cb34e04..25697b856 100644
--- a/src/prop/prop_engine.h
+++ b/src/prop/prop_engine.h
@@ -26,6 +26,9 @@
 #include "expr/node.h"
 #include "util/options.h"
 #include "util/result.h"
+#include "smt/modal_exception.h"
+
+#include <sys/time.h>
 
 namespace CVC4 {
 
@@ -36,6 +39,80 @@ namespace prop {
 class CnfStream;
 class SatSolver;
 
+class PropEngine;
+
+/**
+ * A helper class to keep track of a time budget and signal
+ * the PropEngine when the budget expires.
+ */
+class SatTimer {
+
+  PropEngine& d_propEngine;
+  unsigned long d_ms;
+  timeval d_limit;
+
+public:
+
+  /** Construct a SatTimer attached to the given PropEngine. */
+  SatTimer(PropEngine& propEngine) :
+    d_propEngine(propEngine),
+    d_ms(0) {
+  }
+
+  /** Is the timer currently active? */
+  bool on() const {
+    return d_ms != 0;
+  }
+
+  /** Set a millisecond timer (0==off). */
+  void set(unsigned long millis) {
+    d_ms = millis;
+    // keep track of when it was set, even if it's disabled (i.e. == 0)
+    Trace("limit") << "SatTimer::set(" << d_ms << ")" << std::endl;
+    gettimeofday(&d_limit, NULL);
+    Trace("limit") << "SatTimer::set(): it's " << d_limit.tv_sec << "," << d_limit.tv_usec << std::endl;
+    d_limit.tv_sec += millis / 1000;
+    d_limit.tv_usec += (millis % 1000) * 1000;
+    if(d_limit.tv_usec > 1000000) {
+      ++d_limit.tv_sec;
+      d_limit.tv_usec -= 1000000;
+    }
+    Trace("limit") << "SatTimer::set(): limit is at " << d_limit.tv_sec << "," << d_limit.tv_usec << std::endl;
+  }
+
+  /** Return the milliseconds elapsed since last set(). */
+  unsigned long elapsed() {
+    timeval tv;
+    gettimeofday(&tv, NULL);
+    Trace("limit") << "SatTimer::elapsed(): it's now " << tv.tv_sec << "," << tv.tv_usec << std::endl;
+    tv.tv_sec -= d_limit.tv_sec - d_ms / 1000;
+    tv.tv_usec -= d_limit.tv_usec - (d_ms % 1000) * 1000;
+    Trace("limit") << "SatTimer::elapsed(): elapsed time is " << tv.tv_sec << "," << tv.tv_usec << std::endl;
+    return tv.tv_sec * 1000 + tv.tv_usec / 1000;
+  }
+
+  bool expired() {
+    if(on()) {
+      timeval tv;
+      gettimeofday(&tv, NULL);
+      Trace("limit") << "SatTimer::expired(): current time is " << tv.tv_sec << "," << tv.tv_usec << std::endl;
+      Trace("limit") << "SatTimer::expired(): limit time is " << d_limit.tv_sec << "," << d_limit.tv_usec << std::endl;
+      if(d_limit.tv_sec < tv.tv_sec ||
+         (d_limit.tv_sec == tv.tv_sec && d_limit.tv_usec <= tv.tv_usec)) {
+        Trace("limit") << "SatTimer::expired(): OVER LIMIT!" << std::endl;
+        return true;
+      } else {
+        Trace("limit") << "SatTimer::expired(): within limit" << std::endl;
+      }
+    }
+    return false;
+  }
+
+  /** Check the current time and signal the PropEngine if over-time. */
+  void check();
+
+};/* class SatTimer */
+
 /**
  * PropEngine is the abstraction of a Sat Solver, providing methods for
  * solving the SAT problem and conversion to CNF (via the CnfStream).
@@ -43,7 +120,7 @@ class SatSolver;
 class PropEngine {
 
   /**
-   * Indicates that the sat solver is currently solving something and we should
+   * Indicates that the SAT solver is currently solving something and we should
    * not mess with it's internal state.
    */
   bool d_inCheckSat;
@@ -51,6 +128,7 @@ class PropEngine {
   /** The theory engine we will be using */
   TheoryEngine *d_theoryEngine;
 
+  /** The context */
   context::Context* d_context;
 
   /** The SAT solver proxy */
@@ -62,6 +140,13 @@ class PropEngine {
   /** The CNF converter in use */
   CnfStream* d_cnfStream;
 
+  /** A timer for SAT calls */
+  SatTimer d_satTimer;
+
+  /** Whether we were just interrupted (or not) */
+  bool d_interrupted;
+
+  /** Dump out the satisfying assignment (after SAT result) */
   void printSatisfyingAssignment();
 
 public:
@@ -86,27 +171,34 @@ public:
   void shutdown() { }
 
   /**
-   * Converts the given formula to CNF and assert the CNF to the sat solver.
+   * Converts the given formula to CNF and assert the CNF to the SAT solver.
    * The formula is asserted permanently for the current context.
    * @param node the formula to assert
    */
   void assertFormula(TNode node);
 
   /**
-   * Converts the given formula to CNF and assert the CNF to the sat solver.
-   * The formula can be removed by the sat solver after backtracking lower
+   * Converts the given formula to CNF and assert the CNF to the SAT solver.
+   * The formula can be removed by the SAT solver after backtracking lower
    * than the (SAT and SMT) level at which it was asserted.
    *
    * @param node the formula to assert
-   * @param negated whether the node should be considered to be negated at the top level (or not)
-   * @param removable whether this lemma can be quietly removed based on an activity heuristic (or not)
+   * @param negated whether the node should be considered to be negated
+   * at the top level (or not)
+   * @param removable whether this lemma can be quietly removed based
+   * on an activity heuristic (or not)
    */
   void assertLemma(TNode node, bool negated, bool removable);
 
   /**
    * Checks the current context for satisfiability.
+   *
+   * @param millis the time limit for this call in milliseconds
+   * (0==off); on output, it is set to the milliseconds used
+   * @param on input, resource the number of resource units permitted
+   * for this call (0==off); on output, it is set to the resource used
    */
-  Result checkSat();
+  Result checkSat(unsigned long& millis, unsigned long& resource);
 
   /**
    * Get the value of a boolean variable.
@@ -116,12 +208,19 @@ public:
    */
   Node getValue(TNode node);
 
-  /*
-   * Return true if node has an associated SAT literal
+  /**
+   * Return true if node has an associated SAT literal.
    */
   bool isSatLiteral(TNode node);
 
   /**
+   * Return true if node has an associated SAT literal that is
+   * currently translated (i.e., it's relevant to the current
+   * user push/pop level).
+   */
+  bool isTranslatedSatLiteral(TNode node);
+
+  /**
    * Check if the node has a value and return it if yes.
    */
   bool hasValue(TNode node, bool& value);
@@ -143,8 +242,37 @@ public:
    */
   void pop();
 
+  /**
+   * Check the current time budget.
+   */
+  void checkTime();
+
+  /**
+   * Interrupt a running solver (cause a timeout).
+   */
+  void interrupt() throw(ModalException);
+
+  /**
+   * "Spend" a "resource."  If the sum of these externally-counted
+   * resources and SAT-internal resources exceed the current limit,
+   * SAT should terminate.
+   */
+  void spendResource() throw();
+
 };/* class PropEngine */
 
+
+inline void SatTimer::check() {
+  if(expired()) {
+    Trace("limit") << "SatTimer::check(): interrupt!" << std::endl;
+    d_propEngine.interrupt();
+  }
+}
+
+inline void PropEngine::checkTime() {
+  d_satTimer.check();
+}
+
 }/* CVC4::prop namespace */
 }/* CVC4 namespace */
 
diff --git a/src/prop/sat.cpp b/src/prop/sat.cpp
index 386fb5aad..5d53bf100 100644
--- a/src/prop/sat.cpp
+++ b/src/prop/sat.cpp
@@ -83,6 +83,7 @@ TNode SatSolver::getNode(SatLiteral lit) {
 }
 
 void SatSolver::notifyRestart() {
+  d_propEngine->checkTime();
   d_theoryEngine->notifyRestart();
 }
 
@@ -108,6 +109,9 @@ void SatSolver::logDecision(SatLiteral lit) {
 #endif /* CVC4_REPLAY */
 }
 
+void SatSolver::checkTime() {
+  d_propEngine->checkTime();
+}
 
 }/* CVC4::prop namespace */
 }/* CVC4 namespace */
diff --git a/src/prop/sat.h b/src/prop/sat.h
index ee3978555..026193eae 100644
--- a/src/prop/sat.h
+++ b/src/prop/sat.h
@@ -114,6 +114,8 @@ public:
   virtual void unregisterVar(SatLiteral lit) = 0;
   /** Register the variable (of the literal) for solving */
   virtual void renewVar(SatLiteral lit, int level = -1) = 0;
+  /** Interrupt the solver */
+  virtual void interrupt() = 0;
 };
 
 /**
@@ -214,7 +216,7 @@ public:
 
   virtual ~SatSolver();
 
-  bool solve();
+  SatLiteralValue solve(unsigned long& resource);
 
   void addClause(SatClause& clause, bool removable);
 
@@ -253,6 +255,8 @@ public:
 
   void renewVar(SatLiteral lit, int level = -1);
 
+  void interrupt();
+
   TNode getNode(SatLiteral lit);
 
   void notifyRestart();
@@ -261,6 +265,8 @@ public:
 
   void logDecision(SatLiteral lit);
 
+  void checkTime();
+
 };/* class SatSolver */
 
 /* Functions that delegate to the concrete SAT solver. */
@@ -293,8 +299,20 @@ inline SatSolver::~SatSolver() {
   delete d_minisat;
 }
 
-inline bool SatSolver::solve() {
-  return d_minisat->solve();
+inline SatLiteralValue SatSolver::solve(unsigned long& resource) {
+  Trace("limit") << "SatSolver::solve(): have limit of " << resource << " conflicts" << std::endl;
+  if(resource == 0) {
+    d_minisat->budgetOff();
+  } else {
+    d_minisat->setConfBudget(resource);
+  }
+  Minisat::vec<SatLiteral> empty;
+  unsigned long conflictsBefore = d_minisat->conflicts;
+  SatLiteralValue result = d_minisat->solveLimited(empty);
+  d_minisat->clearInterrupt();
+  resource = d_minisat->conflicts - conflictsBefore;
+  Trace("limit") << "SatSolver::solve(): it took " << resource << " conflicts" << std::endl;
+  return result;
 }
 
 inline void SatSolver::addClause(SatClause& clause, bool removable) {
@@ -333,6 +351,10 @@ inline void SatSolver::renewVar(SatLiteral lit, int level) {
   d_minisat->renewVar(lit, level);
 }
 
+inline void SatSolver::interrupt() {
+  d_minisat->interrupt();
+}
+
 #endif /* __CVC4_USE_MINISAT */
 
 inline size_t