support failure in constraints propagation and demon executions

examples/tests/test_cp_api.py

@@ -64,7 +64,7 @@ def test_search_monitor():
   solver.Solve(db, monitor)
 
 
-class DemonTest(pywrapcp.Demon):
+class DemonTest(pywrapcp.PyDemon):
   def __init__(self, x):
     pywrapcp.Demon.__init__(self)
     self._x = x
@@ -74,7 +74,7 @@ class DemonTest(pywrapcp.Demon):
     print 'in Run(), saw ' + str(self._x)
 
 
-class ConstraintTest(pywrapcp.Constraint):
+class ConstraintTest(pywrapcp.PyConstraint):
   def __init__(self, solver, x):
     pywrapcp.Constraint.__init__(self, solver)
     self._x = x
@@ -92,6 +92,14 @@ class ConstraintTest(pywrapcp.Constraint):
     print self._x
     print 'out of InitialPropagate()'
 
+class InitialPropagateDemon(pywrapcp.PyDemon):
+  def __init__(self, ct):
+    pywrapcp.Demon.__init__(self)
+    self._ct = ct
+
+  def Run(self, solver):
+    self._ct.InitialPropagate()
+
 
 def test_demon():
   solver = pywrapcp.Solver('test export')
@@ -109,6 +117,32 @@ def test_constraint():
   solver.Solve(db)
 
 
+class DumbGreaterOrEqualToFive(pywrapcp.PyConstraint):
+  def __init__(self, solver, x):
+    pywrapcp.Constraint.__init__(self, solver)
+    self._x = x
+
+  def Post(self):
+    self._demon = InitialPropagateDemon(self)
+    self._x.WhenBound(self._demon)
+
+  def InitialPropagate(self):
+    if self._x.Bound():
+      if self._x.Value() < 5:
+        print 'Reject %d' % self._x.Value()
+        self.solver().Fail()
+      else:
+        print 'Accept %d' % self._x.Value()
+
+
+def test_failing_constraint():
+  solver = pywrapcp.Solver('test export')
+  x = solver.IntVar(1, 10, 'x')
+  myct = DumbGreaterOrEqualToFive(solver, x)
+  solver.Add(myct)
+  db = solver.Phase([x], solver.CHOOSE_FIRST_UNBOUND, solver.ASSIGN_MIN_VALUE)
+  solver.Solve(db)
+
 
 def main():
   test_member()
@@ -119,6 +153,7 @@ def main():
   test_search_monitor()
   test_demon()
   test_constraint()
+  test_failing_constraint()
 
 
 if __name__ == '__main__':

src/constraint_solver/constraint_solver.cc

@@ -242,12 +242,14 @@ class Queue {
         solver_->TopPeriodicCheck();
       }
       demon->Run(solver_);
+      solver_->CheckFail();
     } else {
       solver_->GetPropagationMonitor()->BeginDemonRun(demon);
       if (++solver_->demon_runs_[demon->priority()] % kTestPeriod == 0) {
         solver_->TopPeriodicCheck();
       }
       demon->Run(solver_);
+      solver_->CheckFail();
       solver_->GetPropagationMonitor()->EndDemonRun(demon);
     }
   }
@@ -257,6 +259,7 @@ class Queue {
       solver_->TopPeriodicCheck();
     }
     demon->Run(solver_);
+    solver_->CheckFail();
   }
 
   void ProcessInstrumentedNormalDemon(Demon* const demon) {
@@ -265,6 +268,7 @@ class Queue {
       solver_->TopPeriodicCheck();
     }
     demon->Run(solver_);
+    solver_->CheckFail();
     solver_->GetPropagationMonitor()->EndDemonRun(demon);
   }
 
@@ -307,6 +311,7 @@ class Queue {
             solver_->TopPeriodicCheck();
           }
           demon->Run(solver_);
+          solver_->CheckFail();
         }
       }
     } else {
@@ -1420,7 +1425,8 @@ Solver::Solver(const std::string& name, const SolverParameters& parameters)
       additional_constraint_index_(0),
       propagation_monitor_(BuildTrace(this)),
       print_trace_(nullptr),
-      anonymous_variable_index_(0) {
+      anonymous_variable_index_(0) ,
+      should_fail_(false) {
   Init();
 }
 
@@ -1453,7 +1459,8 @@ Solver::Solver(const std::string& name)
       additional_constraint_index_(0),
       propagation_monitor_(BuildTrace(this)),
       print_trace_(nullptr),
-      anonymous_variable_index_(0) {
+      anonymous_variable_index_(0),
+      should_fail_(false) {
   Init();
 }
 
@@ -2460,6 +2467,17 @@ void Solver::Fail() {
   searches_.back()->JumpBack();
 }
 
+void Solver::ShouldFail() {
+  should_fail_ = true;
+}
+
+void Solver::CheckFail() {
+  if (should_fail_) {
+    should_fail_ = false;
+    Fail();
+  }
+}
+
 // ----- Cast Expression -----
 
 IntExpr* Solver::CastExpression(const IntVar* const var) const {
@@ -3214,6 +3232,7 @@ void Constraint::PostAndPropagate() {
   FreezeQueue();
   Post();
   InitialPropagate();
+  solver()->CheckFail();
   UnfreezeQueue();
 }
 

src/constraint_solver/constraint_solver.h

@@ -2883,6 +2883,10 @@ class Solver {
   // method returns expr, nullptr otherwise.
   IntExpr* CastExpression(const IntVar* const var) const;
 
+  // Support for swig.
+  void ShouldFail();
+  void CheckFail();
+
  private:
   void Init();  // Initialization. To be called by the constructors only.
   void PushState(MarkerType t, const StateInfo& info);
@@ -3021,6 +3025,7 @@ class Solver {
   std::unique_ptr<PropagationMonitor> propagation_monitor_;
   PropagationMonitor* print_trace_;
   int anonymous_variable_index_;
+  bool should_fail_;
 
   DISALLOW_COPY_AND_ASSIGN(Solver);
 };

src/constraint_solver/constraint_solver.swig

@@ -260,22 +260,14 @@ gflags.DEFINE_boolean('cp_no_solve', False,
 gflags.DEFINE_string('cp_profile_file', '',
                      'exports profiling overview to file.')
 }
-%pythoncode {
-
-class PyDecisionBuilder(object):
-  def NextWrapper(self, solver):
-    result = None
-    try:
-      result = self.Next(solver)
-    except Exception:
-      return solver.FailDecision()
-    return result
-
-  def DebugString(self):
-    return "PyDecisionBuilder"
-}
 }  // namespace operations_research
 
+// Rename rules for directors
+%rename (InitialPropagateWrapper)
+    operations_research::Constraint::InitialPropagate;
+%rename (RunWrapper) operations_research::Demon::Run;
+
+
 // Rename rules on SolutionCollector.
 %rename (Branches) operations_research::SolutionCollector::branches;
 %rename (Failures) operations_research::SolutionCollector::failures;
@@ -1260,7 +1252,7 @@ struct FailureProtect {
 // Generic rename rule.
 %rename("%(camelcase)s", %$isfunction) "";
 
-// Rename rule on DecisionBuilder;
+// Rename rule on directors;
 %rename (NextWrap) operations_research::DecisionBuilder::Next;
 
 // Rename rule on SearchLimit
@@ -2098,3 +2090,49 @@ namespace operations_research {
 typedef Assignment::AssignmentContainer AssignmentContainer;
 %template(AssignmentIntContainer) AssignmentContainer<IntVar, IntVarElement>;
 }
+
+#if defined(SWIGPYTHON)
+%pythoncode {
+class PyDecisionBuilder(object):
+  def NextWrapper(self, solver):
+    result = None
+    try:
+      result = self.Next(solver)
+    except Exception:
+      return solver.FailDecision()
+    return result
+
+  def DebugString(self):
+    return "PyDecisionBuilder"
+
+
+class PyConstraint(Constraint):
+  def __init__(self, solver):
+    pywrapcp.Constraint.__init__(self, solver)
+
+  def InitialPropagateWrapper(self):
+    try:
+      self.InitialPropagate()
+    except:
+      self.solver().ShouldFail()
+
+  def DebugString(self):
+    return "PyConstraint"
+
+
+class PyDemon(Demon):
+  def __init__(self):
+    pywrapcp.Demon.__init__(self)
+
+  def RunWrapper(self, solver):
+    try:
+      self.Run(solver)
+    except:
+      solver.ShouldFail()
+
+  def DebugString(self):
+    return "PyDemon"
+
+}
+#endif  // SWIGPYTHON
+