Do not set values for non-linear mult terms in collectModelInfo (#3983)

Fixes #3803.

When non-linear arithmetic determines there is a model, then it should not send model values for multiplication terms that the linear solver assigned when abstracting (non-linear) multiplication. This avoids conflicts if the non-linear solver changed a value for a variable occurring in a non-linear monomial. This avoids check-model failures.

1 files changed, 17 insertions, 1 deletions

diff --git a/src/theory/arith/nl_model.cpp b/src/theory/arith/nl_model.cpp
index 904300004..abb2a7921 100644
--- a/src/theory/arith/nl_model.cpp
+++ b/src/theory/arith/nl_model.cpp
@@ -1277,11 +1277,12 @@ void NlModel::getModelValueRepair(
     std::map<Node, Node>& arithModel,
     std::map<Node, std::pair<Node, Node>>& approximations)
 {
+  Trace("nl-model") << "NlModel::getModelValueRepair:" << std::endl;
+
   // Record the approximations we used. This code calls the
   // recordApproximation method of the model, which overrides the model
   // values for variables that we solved for, using techniques specific to
   // this class.
-  Trace("nl-model") << "NlModel::getModelValueRepair:" << std::endl;
   NodeManager* nm = NodeManager::currentNM();
   for (const std::pair<const Node, std::pair<Node, Node> >& cb :
        d_check_model_bounds)
@@ -1324,6 +1325,21 @@ void NlModel::getModelValueRepair(
     arithModel[v] = s;
     Trace("nl-model") << v << " solved is " << s << std::endl;
   }
+
+  // multiplication terms should not be given values; their values are
+  // implied by the monomials that they consist of
+  std::vector<Node> amErase;
+  for (const std::pair<const Node, Node>& am : arithModel)
+  {
+    if (am.first.getKind() == NONLINEAR_MULT)
+    {
+      amErase.push_back(am.first);
+    }
+  }
+  for (const Node& ae : amErase)
+  {
+    arithModel.erase(ae);
+  }
 }
 
 }  // namespace arith