(Move-only) Refactor and document theory model part 2 (#1305)

* Move type set to its own file and document.

* Move theory engine model builder to its own class.

* Working on documentation.

* Document Theory Model.

* Minor

* Document theory model builder.

* Clang format

* Address review.

1 files changed, 1144 insertions, 0 deletions

diff --git a/src/theory/theory_model_builder.cpp b/src/theory/theory_model_builder.cpp
new file mode 100644
index 000000000..b08c8f1ca
--- /dev/null
+++ b/src/theory/theory_model_builder.cpp
@@ -0,0 +1,1144 @@
+/*********************                                                        */
+/*! \file theory_model_builder.cpp
+ ** \verbatim
+ ** Top contributors (to current version):
+ **   Clark Barrett, Andrew Reynolds, Morgan Deters
+ ** This file is part of the CVC4 project.
+ ** Copyright (c) 2009-2017 by the authors listed in the file AUTHORS
+ ** in the top-level source directory) and their institutional affiliations.
+ ** All rights reserved.  See the file COPYING in the top-level source
+ ** directory for licensing information.\endverbatim
+ **
+ ** \brief Implementation of theory model buidler class
+ **/
+#include "theory/theory_model_builder.h"
+
+#include "options/quantifiers_options.h"
+#include "options/smt_options.h"
+#include "options/uf_options.h"
+#include "theory/theory_engine.h"
+#include "theory/uf/theory_uf_model.h"
+
+using namespace std;
+using namespace CVC4::kind;
+using namespace CVC4::context;
+
+namespace CVC4 {
+namespace theory {
+
+TheoryEngineModelBuilder::TheoryEngineModelBuilder(TheoryEngine* te) : d_te(te)
+{
+}
+
+bool TheoryEngineModelBuilder::isAssignable(TNode n)
+{
+  if (n.getKind() == kind::SELECT || n.getKind() == kind::APPLY_SELECTOR_TOTAL)
+  {
+    // selectors are always assignable (where we guarantee that they are not
+    // evaluatable here)
+    if (!options::ufHo())
+    {
+      Assert(!n.getType().isFunction());
+      return true;
+    }
+    else
+    {
+      // might be a function field
+      return !n.getType().isFunction();
+    }
+  }
+  else
+  {
+    // non-function variables, and fully applied functions
+    if (!options::ufHo())
+    {
+      // no functions exist, all functions are fully applied
+      Assert(n.getKind() != kind::HO_APPLY);
+      Assert(!n.getType().isFunction());
+      return n.isVar() || n.getKind() == kind::APPLY_UF;
+    }
+    else
+    {
+      // Assert( n.getKind() != kind::APPLY_UF );
+      return (n.isVar() && !n.getType().isFunction())
+             || n.getKind() == kind::APPLY_UF
+             || (n.getKind() == kind::HO_APPLY
+                 && n[0].getType().getNumChildren() == 2);
+    }
+  }
+}
+
+void TheoryEngineModelBuilder::addAssignableSubterms(TNode n,
+                                                     TheoryModel* tm,
+                                                     NodeSet& cache)
+{
+  if (n.getKind() == FORALL || n.getKind() == EXISTS)
+  {
+    return;
+  }
+  if (cache.find(n) != cache.end())
+  {
+    return;
+  }
+  if (isAssignable(n))
+  {
+    tm->d_equalityEngine->addTerm(n);
+  }
+  for (TNode::iterator child_it = n.begin(); child_it != n.end(); ++child_it)
+  {
+    addAssignableSubterms(*child_it, tm, cache);
+  }
+  cache.insert(n);
+}
+
+void TheoryEngineModelBuilder::assignConstantRep(TheoryModel* tm,
+                                                 Node eqc,
+                                                 Node const_rep)
+{
+  d_constantReps[eqc] = const_rep;
+  Trace("model-builder") << "    Assign: Setting constant rep of " << eqc
+                         << " to " << const_rep << endl;
+  tm->d_rep_set.setTermForRepresentative(const_rep, eqc);
+}
+
+bool TheoryEngineModelBuilder::isExcludedCdtValue(
+    Node val,
+    std::set<Node>* repSet,
+    std::map<Node, Node>& assertedReps,
+    Node eqc)
+{
+  Trace("model-builder-debug")
+      << "Is " << val << " and excluded codatatype value for " << eqc << "? "
+      << std::endl;
+  for (set<Node>::iterator i = repSet->begin(); i != repSet->end(); ++i)
+  {
+    Assert(assertedReps.find(*i) != assertedReps.end());
+    Node rep = assertedReps[*i];
+    Trace("model-builder-debug") << "  Rep : " << rep << std::endl;
+    // check matching val to rep with eqc as a free variable
+    Node eqc_m;
+    if (isCdtValueMatch(val, rep, eqc, eqc_m))
+    {
+      Trace("model-builder-debug") << "  ...matches with " << eqc << " -> "
+                                   << eqc_m << std::endl;
+      if (eqc_m.getKind() == kind::UNINTERPRETED_CONSTANT)
+      {
+        Trace("model-builder-debug") << "*** " << val
+                                     << " is excluded datatype for " << eqc
+                                     << std::endl;
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+bool TheoryEngineModelBuilder::isCdtValueMatch(Node v,
+                                               Node r,
+                                               Node eqc,
+                                               Node& eqc_m)
+{
+  if (r == v)
+  {
+    return true;
+  }
+  else if (r == eqc)
+  {
+    if (eqc_m.isNull())
+    {
+      // only if an uninterpreted constant?
+      eqc_m = v;
+      return true;
+    }
+    else
+    {
+      return v == eqc_m;
+    }
+  }
+  else if (v.getKind() == kind::APPLY_CONSTRUCTOR
+           && r.getKind() == kind::APPLY_CONSTRUCTOR)
+  {
+    if (v.getOperator() == r.getOperator())
+    {
+      for (unsigned i = 0; i < v.getNumChildren(); i++)
+      {
+        if (!isCdtValueMatch(v[i], r[i], eqc, eqc_m))
+        {
+          return false;
+        }
+      }
+      return true;
+    }
+  }
+  return false;
+}
+
+bool TheoryEngineModelBuilder::involvesUSort(TypeNode tn)
+{
+  if (tn.isSort())
+  {
+    return true;
+  }
+  else if (tn.isArray())
+  {
+    return involvesUSort(tn.getArrayIndexType())
+           || involvesUSort(tn.getArrayConstituentType());
+  }
+  else if (tn.isSet())
+  {
+    return involvesUSort(tn.getSetElementType());
+  }
+  else if (tn.isDatatype())
+  {
+    const Datatype& dt = ((DatatypeType)(tn).toType()).getDatatype();
+    return dt.involvesUninterpretedType();
+  }
+  else
+  {
+    return false;
+  }
+}
+
+bool TheoryEngineModelBuilder::isExcludedUSortValue(
+    std::map<TypeNode, unsigned>& eqc_usort_count,
+    Node v,
+    std::map<Node, bool>& visited)
+{
+  Assert(v.isConst());
+  if (visited.find(v) == visited.end())
+  {
+    visited[v] = true;
+    TypeNode tn = v.getType();
+    if (tn.isSort())
+    {
+      Trace("model-builder-debug") << "Is excluded usort value : " << v << " "
+                                   << tn << std::endl;
+      unsigned card = eqc_usort_count[tn];
+      Trace("model-builder-debug") << "  Cardinality is " << card << std::endl;
+      unsigned index =
+          v.getConst<UninterpretedConstant>().getIndex().toUnsignedInt();
+      Trace("model-builder-debug") << "  Index is " << index << std::endl;
+      return index > 0 && index >= card;
+    }
+    for (unsigned i = 0; i < v.getNumChildren(); i++)
+    {
+      if (isExcludedUSortValue(eqc_usort_count, v[i], visited))
+      {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+void TheoryEngineModelBuilder::addToTypeList(
+    TypeNode tn,
+    std::vector<TypeNode>& type_list,
+    std::unordered_set<TypeNode, TypeNodeHashFunction>& visiting)
+{
+  if (std::find(type_list.begin(), type_list.end(), tn) == type_list.end())
+  {
+    if (visiting.find(tn) == visiting.end())
+    {
+      visiting.insert(tn);
+      /* This must make a recursive call on all types that are subterms of
+       * values of the current type.
+       * Note that recursive traversal here is over enumerated expressions
+       * (very low expression depth). */
+      if (tn.isArray())
+      {
+        addToTypeList(tn.getArrayIndexType(), type_list, visiting);
+        addToTypeList(tn.getArrayConstituentType(), type_list, visiting);
+      }
+      else if (tn.isSet())
+      {
+        addToTypeList(tn.getSetElementType(), type_list, visiting);
+      }
+      else if (tn.isDatatype())
+      {
+        const Datatype& dt = ((DatatypeType)(tn).toType()).getDatatype();
+        for (unsigned i = 0; i < dt.getNumConstructors(); i++)
+        {
+          for (unsigned j = 0; j < dt[i].getNumArgs(); j++)
+          {
+            TypeNode ctn = TypeNode::fromType(dt[i][j].getRangeType());
+            addToTypeList(ctn, type_list, visiting);
+          }
+        }
+      }
+      Assert(std::find(type_list.begin(), type_list.end(), tn)
+             == type_list.end());
+      type_list.push_back(tn);
+    }
+  }
+}
+
+bool TheoryEngineModelBuilder::buildModel(Model* m)
+{
+  Trace("model-builder") << "TheoryEngineModelBuilder: buildModel" << std::endl;
+  TheoryModel* tm = (TheoryModel*)m;
+
+  // buildModel should only be called once per check
+  Assert(!tm->isBuilt());
+
+  // Reset model
+  tm->reset();
+
+  // mark as built
+  tm->d_modelBuilt = true;
+
+  // Collect model info from the theories
+  Trace("model-builder") << "TheoryEngineModelBuilder: Collect model info..."
+                         << std::endl;
+  d_te->collectModelInfo(tm);
+
+  // model-builder specific initialization
+  if (!preProcessBuildModel(tm))
+  {
+    return false;
+  }
+
+  // Loop through all terms and make sure that assignable sub-terms are in the
+  // equality engine
+  // Also, record #eqc per type (for finite model finding)
+  std::map<TypeNode, unsigned> eqc_usort_count;
+  eq::EqClassesIterator eqcs_i = eq::EqClassesIterator(tm->d_equalityEngine);
+  {
+    NodeSet cache;
+    for (; !eqcs_i.isFinished(); ++eqcs_i)
+    {
+      eq::EqClassIterator eqc_i =
+          eq::EqClassIterator((*eqcs_i), tm->d_equalityEngine);
+      for (; !eqc_i.isFinished(); ++eqc_i)
+      {
+        addAssignableSubterms(*eqc_i, tm, cache);
+      }
+      TypeNode tn = (*eqcs_i).getType();
+      if (tn.isSort())
+      {
+        if (eqc_usort_count.find(tn) == eqc_usort_count.end())
+        {
+          eqc_usort_count[tn] = 1;
+        }
+        else
+        {
+          eqc_usort_count[tn]++;
+        }
+      }
+    }
+  }
+
+  Trace("model-builder") << "Collect representatives..." << std::endl;
+
+  // Process all terms in the equality engine, store representatives for each EC
+  d_constantReps.clear();
+  std::map<Node, Node> assertedReps;
+  TypeSet typeConstSet, typeRepSet, typeNoRepSet;
+  TypeEnumeratorProperties tep;
+  if (options::finiteModelFind())
+  {
+    tep.d_fixed_usort_card = true;
+    for (std::map<TypeNode, unsigned>::iterator it = eqc_usort_count.begin();
+         it != eqc_usort_count.end();
+         ++it)
+    {
+      Trace("model-builder") << "Fixed bound (#eqc) for " << it->first << " : "
+                             << it->second << std::endl;
+      tep.d_fixed_card[it->first] = Integer(it->second);
+    }
+    typeConstSet.setTypeEnumeratorProperties(&tep);
+  }
+  // AJR: build ordered list of types that ensures that base types are
+  // enumerated first.
+  //   (I think) this is only strictly necessary for finite model finding +
+  //   parametric types
+  //   instantiated with uninterpreted sorts, but is probably a good idea to do
+  //   in general
+  //   since it leads to models with smaller term sizes.
+  std::vector<TypeNode> type_list;
+  eqcs_i = eq::EqClassesIterator(tm->d_equalityEngine);
+  for (; !eqcs_i.isFinished(); ++eqcs_i)
+  {
+    // eqc is the equivalence class representative
+    Node eqc = (*eqcs_i);
+    Trace("model-builder") << "Processing EC: " << eqc << endl;
+    Assert(tm->d_equalityEngine->getRepresentative(eqc) == eqc);
+    TypeNode eqct = eqc.getType();
+    Assert(assertedReps.find(eqc) == assertedReps.end());
+    Assert(d_constantReps.find(eqc) == d_constantReps.end());
+
+    // Loop through terms in this EC
+    Node rep, const_rep;
+    eq::EqClassIterator eqc_i = eq::EqClassIterator(eqc, tm->d_equalityEngine);
+    for (; !eqc_i.isFinished(); ++eqc_i)
+    {
+      Node n = *eqc_i;
+      Trace("model-builder") << "  Processing Term: " << n << endl;
+      // Record as rep if this node was specified as a representative
+      if (tm->d_reps.find(n) != tm->d_reps.end())
+      {
+        // AJR: I believe this assertion is too strict,
+        // e.g. datatypes may assert representative for two constructor terms
+        // that are not in the care graph and are merged during
+        // collectModelInfo.
+        // Assert(rep.isNull());
+        rep = tm->d_reps[n];
+        Assert(!rep.isNull());
+        Trace("model-builder") << "  Rep( " << eqc << " ) = " << rep
+                               << std::endl;
+      }
+      // Record as const_rep if this node is constant
+      if (n.isConst())
+      {
+        Assert(const_rep.isNull());
+        const_rep = n;
+        Trace("model-builder") << "  ConstRep( " << eqc << " ) = " << const_rep
+                               << std::endl;
+      }
+      // model-specific processing of the term
+      tm->addTerm(n);
+    }
+
+    // Assign representative for this EC
+    if (!const_rep.isNull())
+    {
+      // Theories should not specify a rep if there is already a constant in the
+      // EC
+      // AJR: I believe this assertion is too strict, eqc with asserted reps may
+      // merge with constant eqc
+      // Assert(rep.isNull() || rep == const_rep);
+      assignConstantRep(tm, eqc, const_rep);
+      typeConstSet.add(eqct.getBaseType(), const_rep);
+    }
+    else if (!rep.isNull())
+    {
+      assertedReps[eqc] = rep;
+      typeRepSet.add(eqct.getBaseType(), eqc);
+      std::unordered_set<TypeNode, TypeNodeHashFunction> visiting;
+      addToTypeList(eqct.getBaseType(), type_list, visiting);
+    }
+    else
+    {
+      typeNoRepSet.add(eqct, eqc);
+      std::unordered_set<TypeNode, TypeNodeHashFunction> visiting;
+      addToTypeList(eqct, type_list, visiting);
+    }
+  }
+
+  // Need to ensure that each EC has a constant representative.
+
+  Trace("model-builder") << "Processing EC's..." << std::endl;
+
+  TypeSet::iterator it;
+  vector<TypeNode>::iterator type_it;
+  set<Node>::iterator i, i2;
+  bool changed, unassignedAssignable, assignOne = false;
+  set<TypeNode> evaluableSet;
+
+  // Double-fixed-point loop
+  // Outer loop handles a special corner case (see code at end of loop for
+  // details)
+  for (;;)
+  {
+    // Inner fixed-point loop: we are trying to learn constant values for every
+    // EC.  Each time through this loop, we process all of the
+    // types by type and may learn some new EC values.  EC's in one type may
+    // depend on EC's in another type, so we need a fixed-point loop
+    // to ensure that we learn as many EC values as possible
+    do
+    {
+      changed = false;
+      unassignedAssignable = false;
+      evaluableSet.clear();
+
+      // Iterate over all types we've seen
+      for (type_it = type_list.begin(); type_it != type_list.end(); ++type_it)
+      {
+        TypeNode t = *type_it;
+        TypeNode tb = t.getBaseType();
+        set<Node>* noRepSet = typeNoRepSet.getSet(t);
+
+        // 1. Try to evaluate the EC's in this type
+        if (noRepSet != NULL && !noRepSet->empty())
+        {
+          Trace("model-builder") << "  Eval phase, working on type: " << t
+                                 << endl;
+          bool assignable, evaluable, evaluated;
+          d_normalizedCache.clear();
+          for (i = noRepSet->begin(); i != noRepSet->end();)
+          {
+            i2 = i;
+            ++i;
+            assignable = false;
+            evaluable = false;
+            evaluated = false;
+            Trace("model-builder-debug") << "Look at eqc : " << (*i2)
+                                         << std::endl;
+            eq::EqClassIterator eqc_i =
+                eq::EqClassIterator(*i2, tm->d_equalityEngine);
+            for (; !eqc_i.isFinished(); ++eqc_i)
+            {
+              Node n = *eqc_i;
+              Trace("model-builder-debug") << "Look at term : " << n
+                                           << std::endl;
+              if (isAssignable(n))
+              {
+                assignable = true;
+                Trace("model-builder-debug") << "...assignable" << std::endl;
+              }
+              else
+              {
+                evaluable = true;
+                Trace("model-builder-debug") << "...try to normalize"
+                                             << std::endl;
+                Node normalized = normalize(tm, n, true);
+                if (normalized.isConst())
+                {
+                  typeConstSet.add(tb, normalized);
+                  assignConstantRep(tm, *i2, normalized);
+                  Trace("model-builder") << "    Eval: Setting constant rep of "
+                                         << (*i2) << " to " << normalized
+                                         << endl;
+                  changed = true;
+                  evaluated = true;
+                  noRepSet->erase(i2);
+                  break;
+                }
+              }
+            }
+            if (!evaluated)
+            {
+              if (evaluable)
+              {
+                evaluableSet.insert(tb);
+              }
+              if (assignable)
+              {
+                unassignedAssignable = true;
+              }
+            }
+          }
+        }
+
+        // 2. Normalize any non-const representative terms for this type
+        set<Node>* repSet = typeRepSet.getSet(t);
+        if (repSet != NULL && !repSet->empty())
+        {
+          Trace("model-builder")
+              << "  Normalization phase, working on type: " << t << endl;
+          d_normalizedCache.clear();
+          for (i = repSet->begin(); i != repSet->end();)
+          {
+            Assert(assertedReps.find(*i) != assertedReps.end());
+            Node rep = assertedReps[*i];
+            Node normalized = normalize(tm, rep, false);
+            Trace("model-builder") << "    Normalizing rep (" << rep
+                                   << "), normalized to (" << normalized << ")"
+                                   << endl;
+            if (normalized.isConst())
+            {
+              changed = true;
+              typeConstSet.add(tb, normalized);
+              assignConstantRep(tm, *i, normalized);
+              assertedReps.erase(*i);
+              i2 = i;
+              ++i;
+              repSet->erase(i2);
+            }
+            else
+            {
+              if (normalized != rep)
+              {
+                assertedReps[*i] = normalized;
+                changed = true;
+              }
+              ++i;
+            }
+          }
+        }
+      }
+    } while (changed);
+
+    if (!unassignedAssignable)
+    {
+      break;
+    }
+
+    // 3. Assign unassigned assignable EC's using type enumeration - assign a
+    // value *different* from all other EC's if the type is infinite
+    // Assign first value from type enumerator otherwise - for finite types, we
+    // rely on polite framework to ensure that EC's that have to be
+    // different are different.
+
+    // Only make assignments on a type if:
+    // 1. there are no terms that share the same base type with un-normalized
+    // representatives
+    // 2. there are no terms that share teh same base type that are unevaluated
+    // evaluable terms
+    // Alternatively, if 2 or 3 don't hold but we are in a special
+    // deadlock-breaking mode where assignOne is true, go ahead and make one
+    // assignment
+    changed = false;
+    // must iterate over the ordered type list to ensure that we do not
+    // enumerate values with subterms
+    //  having types that we are currently enumerating (when possible)
+    //  for example, this ensures we enumerate uninterpreted sort U before (List
+    //  of U) and (Array U U)
+    //  however, it does not break cyclic type dependencies for mutually
+    //  recursive datatypes, but this is handled
+    //  by recording all subterms of enumerated values in TypeSet::addSubTerms.
+    for (type_it = type_list.begin(); type_it != type_list.end(); ++type_it)
+    {
+      TypeNode t = *type_it;
+      // continue if there are no more equivalence classes of this type to
+      // assign
+      std::set<Node>* noRepSetPtr = typeNoRepSet.getSet(t);
+      if (noRepSetPtr == NULL)
+      {
+        continue;
+      }
+      set<Node>& noRepSet = *noRepSetPtr;
+      if (noRepSet.empty())
+      {
+        continue;
+      }
+
+      // get properties of this type
+      bool isCorecursive = false;
+      if (t.isDatatype())
+      {
+        const Datatype& dt = ((DatatypeType)(t).toType()).getDatatype();
+        isCorecursive =
+            dt.isCodatatype() && (!dt.isFinite(t.toType())
+                                  || dt.isRecursiveSingleton(t.toType()));
+      }
+#ifdef CVC4_ASSERTIONS
+      bool isUSortFiniteRestricted = false;
+      if (options::finiteModelFind())
+      {
+        isUSortFiniteRestricted = !t.isSort() && involvesUSort(t);
+      }
+#endif
+
+      set<Node>* repSet = typeRepSet.getSet(t);
+      TypeNode tb = t.getBaseType();
+      if (!assignOne)
+      {
+        set<Node>* repSet = typeRepSet.getSet(tb);
+        if (repSet != NULL && !repSet->empty())
+        {
+          continue;
+        }
+        if (evaluableSet.find(tb) != evaluableSet.end())
+        {
+          continue;
+        }
+      }
+      Trace("model-builder") << "  Assign phase, working on type: " << t
+                             << endl;
+      bool assignable, evaluable CVC4_UNUSED;
+      for (i = noRepSet.begin(); i != noRepSet.end();)
+      {
+        i2 = i;
+        ++i;
+        eq::EqClassIterator eqc_i =
+            eq::EqClassIterator(*i2, tm->d_equalityEngine);
+        assignable = false;
+        evaluable = false;
+        for (; !eqc_i.isFinished(); ++eqc_i)
+        {
+          Node n = *eqc_i;
+          if (isAssignable(n))
+          {
+            assignable = true;
+          }
+          else
+          {
+            evaluable = true;
+          }
+        }
+        Trace("model-builder-debug")
+            << "    eqc " << *i2 << " is assignable=" << assignable
+            << ", evaluable=" << evaluable << std::endl;
+        if (assignable)
+        {
+          Assert(!evaluable || assignOne);
+          Assert(!t.isBoolean() || (*i2).getKind() == kind::APPLY_UF);
+          Node n;
+          if (t.getCardinality().isInfinite())
+          {
+            // if (!t.isInterpretedFinite()) {
+            bool success;
+            do
+            {
+              Trace("model-builder-debug") << "Enumerate term of type " << t
+                                           << std::endl;
+              n = typeConstSet.nextTypeEnum(t, true);
+              //--- AJR: this code checks whether n is a legal value
+              Assert(!n.isNull());
+              success = true;
+              Trace("model-builder-debug") << "Check if excluded : " << n
+                                           << std::endl;
+#ifdef CVC4_ASSERTIONS
+              if (isUSortFiniteRestricted)
+              {
+                // must not involve uninterpreted constants beyond cardinality
+                // bound (which assumed to coincide with #eqc)
+                // this is just an assertion now, since TypeEnumeratorProperties
+                // should ensure that only legal values are enumerated wrt this
+                // constraint.
+                std::map<Node, bool> visited;
+                success = !isExcludedUSortValue(eqc_usort_count, n, visited);
+                if (!success)
+                {
+                  Trace("model-builder")
+                      << "Excluded value for " << t << " : " << n
+                      << " due to out of range uninterpreted constant."
+                      << std::endl;
+                }
+                Assert(success);
+              }
+#endif
+              if (success && isCorecursive)
+              {
+                if (repSet != NULL && !repSet->empty())
+                {
+                  // in the case of codatatypes, check if it is in the set of
+                  // values that we cannot assign
+                  success = !isExcludedCdtValue(n, repSet, assertedReps, *i2);
+                  if (!success)
+                  {
+                    Trace("model-builder")
+                        << "Excluded value : " << n
+                        << " due to alpha-equivalent codatatype expression."
+                        << std::endl;
+                  }
+                }
+              }
+              //---
+            } while (!success);
+          }
+          else
+          {
+            TypeEnumerator te(t);
+            n = *te;
+          }
+          Assert(!n.isNull());
+          assignConstantRep(tm, *i2, n);
+          changed = true;
+          noRepSet.erase(i2);
+          if (assignOne)
+          {
+            assignOne = false;
+            break;
+          }
+        }
+      }
+    }
+
+    // Corner case - I'm not sure this can even happen - but it's theoretically
+    // possible to have a cyclical dependency
+    // in EC assignment/evaluation, e.g. EC1 = {a, b + 1}; EC2 = {b, a - 1}.  In
+    // this case, neither one will get assigned because we are waiting
+    // to be able to evaluate.  But we will never be able to evaluate because
+    // the variables that need to be assigned are in
+    // these same EC's.  In this case, repeat the whole fixed-point computation
+    // with the difference that the first EC
+    // that has both assignable and evaluable expressions will get assigned.
+    if (!changed)
+    {
+      Assert(!assignOne);  // check for infinite loop!
+      assignOne = true;
+    }
+  }
+
+#ifdef CVC4_ASSERTIONS
+  // Assert that all representatives have been converted to constants
+  for (it = typeRepSet.begin(); it != typeRepSet.end(); ++it)
+  {
+    set<Node>& repSet = TypeSet::getSet(it);
+    if (!repSet.empty())
+    {
+      Trace("model-builder") << "***Non-empty repSet, size = " << repSet.size()
+                             << ", first = " << *(repSet.begin()) << endl;
+      Assert(false);
+    }
+  }
+#endif /* CVC4_ASSERTIONS */
+
+  Trace("model-builder") << "Copy representatives to model..." << std::endl;
+  tm->d_reps.clear();
+  std::map<Node, Node>::iterator itMap;
+  for (itMap = d_constantReps.begin(); itMap != d_constantReps.end(); ++itMap)
+  {
+    tm->d_reps[itMap->first] = itMap->second;
+    tm->d_rep_set.add(itMap->second.getType(), itMap->second);
+  }
+
+  Trace("model-builder") << "Make sure ECs have reps..." << std::endl;
+  // Make sure every EC has a rep
+  for (itMap = assertedReps.begin(); itMap != assertedReps.end(); ++itMap)
+  {
+    tm->d_reps[itMap->first] = itMap->second;
+    tm->d_rep_set.add(itMap->second.getType(), itMap->second);
+  }
+  for (it = typeNoRepSet.begin(); it != typeNoRepSet.end(); ++it)
+  {
+    set<Node>& noRepSet = TypeSet::getSet(it);
+    set<Node>::iterator i;
+    for (i = noRepSet.begin(); i != noRepSet.end(); ++i)
+    {
+      tm->d_reps[*i] = *i;
+      tm->d_rep_set.add((*i).getType(), *i);
+    }
+  }
+
+  // modelBuilder-specific initialization
+  if (!processBuildModel(tm))
+  {
+    return false;
+  }
+  else
+  {
+    return true;
+  }
+}
+
+void TheoryEngineModelBuilder::debugCheckModel(Model* m)
+{
+  TheoryModel* tm = (TheoryModel*)m;
+#ifdef CVC4_ASSERTIONS
+  Assert(tm->isBuilt());
+  eq::EqClassesIterator eqcs_i = eq::EqClassesIterator(tm->d_equalityEngine);
+  std::map<Node, Node>::iterator itMap;
+  // Check that every term evaluates to its representative in the model
+  for (eqcs_i = eq::EqClassesIterator(tm->d_equalityEngine);
+       !eqcs_i.isFinished();
+       ++eqcs_i)
+  {
+    // eqc is the equivalence class representative
+    Node eqc = (*eqcs_i);
+    // get the representative
+    Node rep = tm->getRepresentative(eqc);
+    if (!rep.isConst() && eqc.getType().isBoolean())
+    {
+      // if Boolean, it does not necessarily have a constant representative, use
+      // get value instead
+      rep = tm->getValue(eqc);
+      Assert(rep.isConst());
+    }
+    eq::EqClassIterator eqc_i = eq::EqClassIterator(eqc, tm->d_equalityEngine);
+    for (; !eqc_i.isFinished(); ++eqc_i)
+    {
+      Node n = *eqc_i;
+      static int repCheckInstance = 0;
+      ++repCheckInstance;
+
+      // non-linear mult is not necessarily accurate wrt getValue
+      if (n.getKind() != kind::NONLINEAR_MULT)
+      {
+        Debug("check-model::rep-checking") << "( " << repCheckInstance << ") "
+                                           << "n: " << n << endl
+                                           << "getValue(n): " << tm->getValue(n)
+                                           << endl
+                                           << "rep: " << rep << endl;
+        Assert(tm->getValue(*eqc_i) == rep,
+               "run with -d check-model::rep-checking for details");
+      }
+    }
+  }
+#endif /* CVC4_ASSERTIONS */
+
+  // builder-specific debugging
+  debugModel(tm);
+}
+
+Node TheoryEngineModelBuilder::normalize(TheoryModel* m, TNode r, bool evalOnly)
+{
+  std::map<Node, Node>::iterator itMap = d_constantReps.find(r);
+  if (itMap != d_constantReps.end())
+  {
+    return (*itMap).second;
+  }
+  NodeMap::iterator it = d_normalizedCache.find(r);
+  if (it != d_normalizedCache.end())
+  {
+    return (*it).second;
+  }
+  Trace("model-builder-debug") << "do normalize on " << r << std::endl;
+  Node retNode = r;
+  if (r.getNumChildren() > 0)
+  {
+    std::vector<Node> children;
+    if (r.getMetaKind() == kind::metakind::PARAMETERIZED)
+    {
+      children.push_back(r.getOperator());
+    }
+    bool childrenConst = true;
+    for (size_t i = 0; i < r.getNumChildren(); ++i)
+    {
+      Node ri = r[i];
+      bool recurse = true;
+      if (!ri.isConst())
+      {
+        if (m->d_equalityEngine->hasTerm(ri))
+        {
+          itMap =
+              d_constantReps.find(m->d_equalityEngine->getRepresentative(ri));
+          if (itMap != d_constantReps.end())
+          {
+            ri = (*itMap).second;
+            recurse = false;
+          }
+          else if (!evalOnly)
+          {
+            recurse = false;
+          }
+        }
+        if (recurse)
+        {
+          ri = normalize(m, ri, evalOnly);
+        }
+        if (!ri.isConst())
+        {
+          childrenConst = false;
+        }
+      }
+      children.push_back(ri);
+    }
+    retNode = NodeManager::currentNM()->mkNode(r.getKind(), children);
+    if (childrenConst)
+    {
+      retNode = Rewriter::rewrite(retNode);
+      Assert(retNode.getKind() == kind::APPLY_UF
+             || !retNode.getType().isFirstClass()
+             || retNode.isConst());
+    }
+  }
+  d_normalizedCache[r] = retNode;
+  return retNode;
+}
+
+bool TheoryEngineModelBuilder::preProcessBuildModel(TheoryModel* m)
+{
+  return true;
+}
+
+bool TheoryEngineModelBuilder::processBuildModel(TheoryModel* m)
+{
+  assignFunctions(m);
+  return true;
+}
+
+void TheoryEngineModelBuilder::assignFunction(TheoryModel* m, Node f)
+{
+  Assert(!options::ufHo());
+  uf::UfModelTree ufmt(f);
+  Node default_v;
+  for (size_t i = 0; i < m->d_uf_terms[f].size(); i++)
+  {
+    Node un = m->d_uf_terms[f][i];
+    vector<TNode> children;
+    children.push_back(f);
+    Trace("model-builder-debug") << "  process term : " << un << std::endl;
+    for (size_t j = 0; j < un.getNumChildren(); ++j)
+    {
+      Node rc = m->getRepresentative(un[j]);
+      Trace("model-builder-debug2") << "    get rep : " << un[j] << " returned "
+                                    << rc << std::endl;
+      Assert(rc.isConst());
+      children.push_back(rc);
+    }
+    Node simp = NodeManager::currentNM()->mkNode(un.getKind(), children);
+    Node v = m->getRepresentative(un);
+    Trace("model-builder") << "  Setting (" << simp << ") to (" << v << ")"
+                           << endl;
+    ufmt.setValue(m, simp, v);
+    default_v = v;
+  }
+  if (default_v.isNull())
+  {
+    // choose default value from model if none exists
+    TypeEnumerator te(f.getType().getRangeType());
+    default_v = (*te);
+  }
+  ufmt.setDefaultValue(m, default_v);
+  bool condenseFuncValues = options::condenseFunctionValues();
+  if (condenseFuncValues)
+  {
+    ufmt.simplify();
+  }
+  std::stringstream ss;
+  ss << "_arg_" << f << "_";
+  Node val = ufmt.getFunctionValue(ss.str().c_str(), condenseFuncValues);
+  m->assignFunctionDefinition(f, val);
+  // ufmt.debugPrint( std::cout, m );
+}
+
+void TheoryEngineModelBuilder::assignHoFunction(TheoryModel* m, Node f)
+{
+  Assert(options::ufHo());
+  TypeNode type = f.getType();
+  std::vector<TypeNode> argTypes = type.getArgTypes();
+  std::vector<Node> args;
+  std::vector<TNode> apply_args;
+  for (unsigned i = 0; i < argTypes.size(); i++)
+  {
+    Node v = NodeManager::currentNM()->mkBoundVar(argTypes[i]);
+    args.push_back(v);
+    if (i > 0)
+    {
+      apply_args.push_back(v);
+    }
+  }
+  // start with the base return value (currently we use the same default value
+  // for all functions)
+  TypeEnumerator te(type.getRangeType());
+  Node curr = (*te);
+  std::map<Node, std::vector<Node> >::iterator itht = m->d_ho_uf_terms.find(f);
+  if (itht != m->d_ho_uf_terms.end())
+  {
+    for (size_t i = 0; i < itht->second.size(); i++)
+    {
+      Node hn = itht->second[i];
+      Trace("model-builder-debug") << "    process : " << hn << std::endl;
+      Assert(hn.getKind() == kind::HO_APPLY);
+      Assert(m->areEqual(hn[0], f));
+      Node hni = m->getRepresentative(hn[1]);
+      Trace("model-builder-debug2") << "      get rep : " << hn[0]
+                                    << " returned " << hni << std::endl;
+      Assert(hni.isConst());
+      Assert(hni.getType().isSubtypeOf(args[0].getType()));
+      hni = Rewriter::rewrite(args[0].eqNode(hni));
+      Node hnv = m->getRepresentative(hn);
+      Trace("model-builder-debug2") << "      get rep val : " << hn
+                                    << " returned " << hnv << std::endl;
+      Assert(hnv.isConst());
+      if (!apply_args.empty())
+      {
+        Assert(hnv.getKind() == kind::LAMBDA
+               && hnv[0].getNumChildren() + 1 == args.size());
+        std::vector<TNode> largs;
+        for (unsigned j = 0; j < hnv[0].getNumChildren(); j++)
+        {
+          largs.push_back(hnv[0][j]);
+        }
+        Assert(largs.size() == apply_args.size());
+        hnv = hnv[1].substitute(
+            largs.begin(), largs.end(), apply_args.begin(), apply_args.end());
+        hnv = Rewriter::rewrite(hnv);
+      }
+      Assert(!TypeNode::leastCommonTypeNode(hnv.getType(), curr.getType())
+                  .isNull());
+      curr = NodeManager::currentNM()->mkNode(kind::ITE, hni, hnv, curr);
+    }
+  }
+  Node val = NodeManager::currentNM()->mkNode(
+      kind::LAMBDA,
+      NodeManager::currentNM()->mkNode(kind::BOUND_VAR_LIST, args),
+      curr);
+  m->assignFunctionDefinition(f, val);
+}
+
+// This struct is used to sort terms by the "size" of their type
+//   The size of the type is the number of nodes in the type, for example
+//  size of Int is 1
+//  size of Function( Int, Int ) is 3
+//  size of Function( Function( Bool, Int ), Int ) is 5
+struct sortTypeSize
+{
+  // stores the size of the type
+  std::map<TypeNode, unsigned> d_type_size;
+  // get the size of type tn
+  unsigned getTypeSize(TypeNode tn)
+  {
+    std::map<TypeNode, unsigned>::iterator it = d_type_size.find(tn);
+    if (it != d_type_size.end())
+    {
+      return it->second;
+    }
+    else
+    {
+      unsigned sum = 1;
+      for (unsigned i = 0; i < tn.getNumChildren(); i++)
+      {
+        sum += getTypeSize(tn[i]);
+      }
+      d_type_size[tn] = sum;
+      return sum;
+    }
+  }
+
+ public:
+  // compares the type size of i and j
+  // returns true iff the size of i is less than that of j
+  // tiebreaks are determined by node value
+  bool operator()(Node i, Node j)
+  {
+    int si = getTypeSize(i.getType());
+    int sj = getTypeSize(j.getType());
+    if (si < sj)
+    {
+      return true;
+    }
+    else if (si == sj)
+    {
+      return i < j;
+    }
+    else
+    {
+      return false;
+    }
+  }
+};
+
+void TheoryEngineModelBuilder::assignFunctions(TheoryModel* m)
+{
+  Trace("model-builder") << "Assigning function values..." << std::endl;
+  std::vector<Node> funcs_to_assign = m->getFunctionsToAssign();
+
+  if (options::ufHo())
+  {
+    // sort based on type size if higher-order
+    Trace("model-builder") << "Sort functions by type..." << std::endl;
+    sortTypeSize sts;
+    std::sort(funcs_to_assign.begin(), funcs_to_assign.end(), sts);
+  }
+
+  if (Trace.isOn("model-builder"))
+  {
+    Trace("model-builder") << "...have " << funcs_to_assign.size()
+                           << " functions to assign:" << std::endl;
+    for (unsigned k = 0; k < funcs_to_assign.size(); k++)
+    {
+      Node f = funcs_to_assign[k];
+      Trace("model-builder") << "  [" << k << "] : " << f << " : "
+                             << f.getType() << std::endl;
+    }
+  }
+
+  // construct function values
+  for (unsigned k = 0; k < funcs_to_assign.size(); k++)
+  {
+    Node f = funcs_to_assign[k];
+    Trace("model-builder") << "  Function #" << k << " is " << f << std::endl;
+    // std::map< Node, std::vector< Node > >::iterator itht =
+    // m->d_ho_uf_terms.find( f );
+    if (!options::ufHo())
+    {
+      Trace("model-builder") << "  Assign function value for " << f
+                             << " based on APPLY_UF" << std::endl;
+      assignFunction(m, f);
+    }
+    else
+    {
+      Trace("model-builder") << "  Assign function value for " << f
+                             << " based on curried HO_APPLY" << std::endl;
+      assignHoFunction(m, f);
+    }
+  }
+  Trace("model-builder") << "Finished assigning function values." << std::endl;
+}
+
+} /* namespace CVC4::theory */
+} /* namespace CVC4 */