Refactor non-clausal simplify preprocessing pass. (#2425)

1 files changed, 460 insertions, 0 deletions

diff --git a/src/preprocessing/passes/non_clausal_simp.cpp b/src/preprocessing/passes/non_clausal_simp.cpp
new file mode 100644
index 000000000..e2ce1c301
--- /dev/null
+++ b/src/preprocessing/passes/non_clausal_simp.cpp
@@ -0,0 +1,460 @@
+/*********************                                                        */
+/*! \file non_clausal_simp.cpp
+ ** \verbatim
+ ** Top contributors (to current version):
+ **   Aina Niemetz
+ ** This file is part of the CVC4 project.
+ ** Copyright (c) 2009-2018 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 Non-clausal simplification preprocessing pass.
+ **
+ ** Run the nonclausal solver and try to solve all assigned theory literals.
+ **/
+
+#include "preprocessing/passes/non_clausal_simp.h"
+
+#include "context/cdo.h"
+#include "options/proof_options.h"
+#include "smt/smt_statistics_registry.h"
+#include "theory/theory_model.h"
+
+#include <vector>
+
+using namespace CVC4;
+using namespace CVC4::theory;
+
+namespace CVC4 {
+namespace preprocessing {
+namespace passes {
+
+/* -------------------------------------------------------------------------- */
+
+NonClausalSimp::Statistics::Statistics()
+    : d_numConstantProps(
+          "preprocessing::passes::NonClausalSimp::NumConstantProps", 0)
+{
+  smtStatisticsRegistry()->registerStat(&d_numConstantProps);
+}
+
+NonClausalSimp::Statistics::~Statistics()
+{
+  smtStatisticsRegistry()->unregisterStat(&d_numConstantProps);
+}
+
+/* -------------------------------------------------------------------------- */
+
+NonClausalSimp::NonClausalSimp(PreprocessingPassContext* preprocContext)
+    : PreprocessingPass(preprocContext, "non-clausal-simp")
+{
+}
+
+PreprocessingPassResult NonClausalSimp::applyInternal(
+    AssertionPipeline* assertionsToPreprocess)
+{
+  Assert(!options::unsatCores() && !options::fewerPreprocessingHoles());
+
+  d_preprocContext->spendResource(options::preprocessStep());
+
+  theory::booleans::CircuitPropagator* propagator =
+      d_preprocContext->getCircuitPropagator();
+
+  for (size_t i = 0, size = assertionsToPreprocess->size(); i < size; ++i)
+  {
+    Trace("non-clausal-simplify") << "Assertion #" << i << " : "
+                                  << (*assertionsToPreprocess)[i] << std::endl;
+  }
+
+  if (propagator->getNeedsFinish())
+  {
+    propagator->finish();
+    propagator->setNeedsFinish(false);
+  }
+  propagator->initialize();
+
+  // Assert all the assertions to the propagator
+  Trace("non-clausal-simplify") << "asserting to propagator" << std::endl;
+  context::CDO<unsigned>& substs_index =
+      assertionsToPreprocess->getSubstitutionsIndex();
+  for (size_t i = 0, size = assertionsToPreprocess->size(); i < size; ++i)
+  {
+    Assert(Rewriter::rewrite((*assertionsToPreprocess)[i])
+           == (*assertionsToPreprocess)[i]);
+    // Don't reprocess substitutions
+    if (substs_index > 0 && i == substs_index)
+    {
+      continue;
+    }
+    Trace("non-clausal-simplify")
+        << "asserting " << (*assertionsToPreprocess)[i] << std::endl;
+    Debug("cores") << "propagator->assertTrue: " << (*assertionsToPreprocess)[i]
+                   << std::endl;
+    propagator->assertTrue((*assertionsToPreprocess)[i]);
+  }
+
+  Trace("non-clausal-simplify") << "propagating" << std::endl;
+  if (propagator->propagate())
+  {
+    // If in conflict, just return false
+    Trace("non-clausal-simplify")
+        << "conflict in non-clausal propagation" << std::endl;
+    Assert(!options::unsatCores() && !options::fewerPreprocessingHoles());
+    assertionsToPreprocess->clear();
+    Node n = NodeManager::currentNM()->mkConst<bool>(false);
+    assertionsToPreprocess->push_back(n);
+    PROOF(ProofManager::currentPM()->addDependence(n, Node::null()));
+    propagator->setNeedsFinish(true);
+    return PreprocessingPassResult::CONFLICT;
+  }
+
+  Trace("non-clausal-simplify")
+      << "Iterate through " << propagator->getLearnedLiterals().size()
+      << " learned literals." << std::endl;
+  // No conflict, go through the literals and solve them
+  SubstitutionMap& top_level_substs =
+      assertionsToPreprocess->getTopLevelSubstitutions();
+  SubstitutionMap constantPropagations(d_preprocContext->getUserContext());
+  SubstitutionMap newSubstitutions(d_preprocContext->getUserContext());
+  SubstitutionMap::iterator pos;
+  size_t j = 0;
+  std::vector<Node>& learned_literals = propagator->getLearnedLiterals();
+  for (size_t i = 0, size = learned_literals.size(); i < size; ++i)
+  {
+    // Simplify the literal we learned wrt previous substitutions
+    Node learnedLiteral = learned_literals[i];
+    Assert(Rewriter::rewrite(learnedLiteral) == learnedLiteral);
+    Assert(top_level_substs.apply(learnedLiteral) == learnedLiteral);
+    Trace("non-clausal-simplify")
+        << "Process learnedLiteral : " << learnedLiteral << std::endl;
+    Node learnedLiteralNew = newSubstitutions.apply(learnedLiteral);
+    if (learnedLiteral != learnedLiteralNew)
+    {
+      learnedLiteral = Rewriter::rewrite(learnedLiteralNew);
+    }
+    Trace("non-clausal-simplify")
+        << "Process learnedLiteral, after newSubs : " << learnedLiteral
+        << std::endl;
+    for (;;)
+    {
+      learnedLiteralNew = constantPropagations.apply(learnedLiteral);
+      if (learnedLiteralNew == learnedLiteral)
+      {
+        break;
+      }
+      d_statistics.d_numConstantProps += 1;
+      learnedLiteral = Rewriter::rewrite(learnedLiteralNew);
+    }
+    Trace("non-clausal-simplify")
+        << "Process learnedLiteral, after constProp : " << learnedLiteral
+        << std::endl;
+    // It might just simplify to a constant
+    if (learnedLiteral.isConst())
+    {
+      if (learnedLiteral.getConst<bool>())
+      {
+        // If the learned literal simplifies to true, it's redundant
+        continue;
+      }
+      else
+      {
+        // If the learned literal simplifies to false, we're in conflict
+        Trace("non-clausal-simplify")
+            << "conflict with " << learned_literals[i] << std::endl;
+        Assert(!options::unsatCores());
+        assertionsToPreprocess->clear();
+        Node n = NodeManager::currentNM()->mkConst<bool>(false);
+        assertionsToPreprocess->push_back(n);
+        PROOF(ProofManager::currentPM()->addDependence(n, Node::null()));
+        propagator->setNeedsFinish(true);
+        return PreprocessingPassResult::CONFLICT;
+      }
+    }
+
+    // Solve it with the corresponding theory, possibly adding new
+    // substitutions to newSubstitutions
+    Trace("non-clausal-simplify") << "solving " << learnedLiteral << std::endl;
+
+    Theory::PPAssertStatus solveStatus =
+        d_preprocContext->getTheoryEngine()->solve(learnedLiteral,
+                                                   newSubstitutions);
+
+    switch (solveStatus)
+    {
+      case Theory::PP_ASSERT_STATUS_SOLVED:
+      {
+        // The literal should rewrite to true
+        Trace("non-clausal-simplify")
+            << "solved " << learnedLiteral << std::endl;
+        Assert(Rewriter::rewrite(newSubstitutions.apply(learnedLiteral))
+                   .isConst());
+        //        vector<pair<Node, Node> > equations;
+        //        constantPropagations.simplifyLHS(top_level_substs, equations,
+        //        true); if (equations.empty()) {
+        //          break;
+        //        }
+        //        Assert(equations[0].first.isConst() &&
+        //        equations[0].second.isConst() && equations[0].first !=
+        //        equations[0].second);
+        // else fall through
+        break;
+      }
+      case Theory::PP_ASSERT_STATUS_CONFLICT:
+      {
+        // If in conflict, we return false
+        Trace("non-clausal-simplify")
+            << "conflict while solving " << learnedLiteral << std::endl;
+        Assert(!options::unsatCores());
+        assertionsToPreprocess->clear();
+        Node n = NodeManager::currentNM()->mkConst<bool>(false);
+        assertionsToPreprocess->push_back(n);
+        PROOF(ProofManager::currentPM()->addDependence(n, Node::null()));
+        propagator->setNeedsFinish(true);
+        return PreprocessingPassResult::CONFLICT;
+      }
+      default:
+        if (learnedLiteral.getKind() == kind::EQUAL
+            && (learnedLiteral[0].isConst() || learnedLiteral[1].isConst()))
+        {
+          // constant propagation
+          TNode t;
+          TNode c;
+          if (learnedLiteral[0].isConst())
+          {
+            t = learnedLiteral[1];
+            c = learnedLiteral[0];
+          }
+          else
+          {
+            t = learnedLiteral[0];
+            c = learnedLiteral[1];
+          }
+          Assert(!t.isConst());
+          Assert(constantPropagations.apply(t) == t);
+          Assert(top_level_substs.apply(t) == t);
+          Assert(newSubstitutions.apply(t) == t);
+          constantPropagations.addSubstitution(t, c);
+          // vector<pair<Node,Node> > equations;
+          // constantPropagations.simplifyLHS(t, c, equations, true);
+          // if (!equations.empty()) {
+          //   Assert(equations[0].first.isConst() &&
+          //   equations[0].second.isConst() && equations[0].first !=
+          //   equations[0].second); assertionsToPreprocess->clear();
+          //   Node n = NodeManager::currentNM()->mkConst<bool>(false);
+          //   assertionsToPreprocess->push_back(n);
+          //   PROOF(ProofManager::currentPM()->addDependence(n, Node::null()));
+          //   false); return;
+          // }
+          // top_level_substs.simplifyRHS(constantPropagations);
+        }
+        else
+        {
+          // Keep the literal
+          learned_literals[j++] = learned_literals[i];
+        }
+        break;
+    }
+  }
+
+#ifdef CVC4_ASSERTIONS
+  // NOTE: When debugging this code, consider moving this check inside of the
+  // loop over propagator->getLearnedLiterals(). This check has been moved
+  // outside because it is costly for certain inputs (see bug 508).
+  //
+  // Check data structure invariants:
+  // 1. for each lhs of top_level_substs, does not appear anywhere in rhs of
+  // top_level_substs or anywhere in constantPropagations
+  // 2. each lhs of constantPropagations rewrites to itself
+  // 3. if l -> r is a constant propagation and l is a subterm of l' with l' ->
+  // r' another constant propagation, then l'[l/r] -> r' should be a
+  //    constant propagation too
+  // 4. each lhs of constantPropagations is different from each rhs
+  for (pos = newSubstitutions.begin(); pos != newSubstitutions.end(); ++pos)
+  {
+    Assert((*pos).first.isVar());
+    Assert(top_level_substs.apply((*pos).first) == (*pos).first);
+    Assert(top_level_substs.apply((*pos).second) == (*pos).second);
+    Assert(newSubstitutions.apply(newSubstitutions.apply((*pos).second))
+           == newSubstitutions.apply((*pos).second));
+  }
+  for (pos = constantPropagations.begin(); pos != constantPropagations.end();
+       ++pos)
+  {
+    Assert((*pos).second.isConst());
+    Assert(Rewriter::rewrite((*pos).first) == (*pos).first);
+    // Node newLeft = top_level_substs.apply((*pos).first);
+    // if (newLeft != (*pos).first) {
+    //   newLeft = Rewriter::rewrite(newLeft);
+    //   Assert(newLeft == (*pos).second ||
+    //          (constantPropagations.hasSubstitution(newLeft) &&
+    //          constantPropagations.apply(newLeft) == (*pos).second));
+    // }
+    // newLeft = constantPropagations.apply((*pos).first);
+    // if (newLeft != (*pos).first) {
+    //   newLeft = Rewriter::rewrite(newLeft);
+    //   Assert(newLeft == (*pos).second ||
+    //          (constantPropagations.hasSubstitution(newLeft) &&
+    //          constantPropagations.apply(newLeft) == (*pos).second));
+    // }
+    Assert(constantPropagations.apply((*pos).second) == (*pos).second);
+  }
+#endif /* CVC4_ASSERTIONS */
+
+  // Resize the learnt
+  Trace("non-clausal-simplify")
+      << "Resize non-clausal learned literals to " << j << std::endl;
+  learned_literals.resize(j);
+
+  unordered_set<TNode, TNodeHashFunction> s;
+  for (size_t i = 0, size = assertionsToPreprocess->size(); i < size; ++i)
+  {
+    Node assertion = (*assertionsToPreprocess)[i];
+    Node assertionNew = newSubstitutions.apply(assertion);
+    Trace("non-clausal-simplify") << "assertion = " << assertion << std::endl;
+    Trace("non-clausal-simplify")
+        << "assertionNew = " << assertionNew << std::endl;
+    if (assertion != assertionNew)
+    {
+      assertion = Rewriter::rewrite(assertionNew);
+      Trace("non-clausal-simplify")
+          << "rewrite(assertion) = " << assertion << std::endl;
+    }
+    Assert(Rewriter::rewrite(assertion) == assertion);
+    for (;;)
+    {
+      assertionNew = constantPropagations.apply(assertion);
+      if (assertionNew == assertion)
+      {
+        break;
+      }
+      d_statistics.d_numConstantProps += 1;
+      Trace("non-clausal-simplify")
+          << "assertionNew = " << assertionNew << std::endl;
+      assertion = Rewriter::rewrite(assertionNew);
+      Trace("non-clausal-simplify")
+          << "assertionNew = " << assertionNew << std::endl;
+    }
+    s.insert(assertion);
+    assertionsToPreprocess->replace(i, assertion);
+    Trace("non-clausal-simplify")
+        << "non-clausal preprocessed: " << assertion << std::endl;
+  }
+
+  // add substitutions to model, or as assertions if needed (when incremental)
+  TheoryModel* m = d_preprocContext->getTheoryEngine()->getModel();
+  Assert(m != nullptr);
+  NodeManager* nm = NodeManager::currentNM();
+  NodeBuilder<> substitutionsBuilder(kind::AND);
+  for (pos = newSubstitutions.begin(); pos != newSubstitutions.end(); ++pos)
+  {
+    Node lhs = (*pos).first;
+    Node rhs = newSubstitutions.apply((*pos).second);
+    // If using incremental, we must check whether this variable has occurred
+    // before now. If it hasn't we can add this as a substitution.
+    if (substs_index == 0
+        || d_preprocContext->getSymsInAssertions().find(lhs)
+               == d_preprocContext->getSymsInAssertions().end())
+    {
+      Trace("non-clausal-simplify")
+          << "substitute: " << lhs << " " << rhs << std::endl;
+      m->addSubstitution(lhs, rhs);
+    }
+    else
+    {
+      // if it has, the substitution becomes an assertion
+      Node eq = nm->mkNode(kind::EQUAL, lhs, rhs);
+      Trace("non-clausal-simplify")
+          << "substitute: will notify SAT layer of substitution: " << eq
+          << std::endl;
+      substitutionsBuilder << eq;
+    }
+  }
+  // add to the last assertion if necessary
+  if (substitutionsBuilder.getNumChildren() > 0)
+  {
+    substitutionsBuilder << (*assertionsToPreprocess)[substs_index];
+    assertionsToPreprocess->replace(
+        substs_index, Rewriter::rewrite(Node(substitutionsBuilder)));
+  }
+
+  NodeBuilder<> learnedBuilder(kind::AND);
+  Assert(assertionsToPreprocess->getRealAssertionsEnd()
+         <= assertionsToPreprocess->size());
+  learnedBuilder << (*assertionsToPreprocess)
+          [assertionsToPreprocess->getRealAssertionsEnd() - 1];
+
+  for (size_t i = 0; i < learned_literals.size(); ++i)
+  {
+    Node learned = learned_literals[i];
+    Assert(top_level_substs.apply(learned) == learned);
+    Node learnedNew = newSubstitutions.apply(learned);
+    if (learned != learnedNew)
+    {
+      learned = Rewriter::rewrite(learnedNew);
+    }
+    Assert(Rewriter::rewrite(learned) == learned);
+    for (;;)
+    {
+      learnedNew = constantPropagations.apply(learned);
+      if (learnedNew == learned)
+      {
+        break;
+      }
+      d_statistics.d_numConstantProps += 1;
+      learned = Rewriter::rewrite(learnedNew);
+    }
+    if (s.find(learned) != s.end())
+    {
+      continue;
+    }
+    s.insert(learned);
+    learnedBuilder << learned;
+    Trace("non-clausal-simplify")
+        << "non-clausal learned : " << learned << std::endl;
+  }
+  learned_literals.clear();
+
+  for (pos = constantPropagations.begin(); pos != constantPropagations.end();
+       ++pos)
+  {
+    Node cProp = (*pos).first.eqNode((*pos).second);
+    Assert(top_level_substs.apply(cProp) == cProp);
+    Node cPropNew = newSubstitutions.apply(cProp);
+    if (cProp != cPropNew)
+    {
+      cProp = Rewriter::rewrite(cPropNew);
+      Assert(Rewriter::rewrite(cProp) == cProp);
+    }
+    if (s.find(cProp) != s.end())
+    {
+      continue;
+    }
+    s.insert(cProp);
+    learnedBuilder << cProp;
+    Trace("non-clausal-simplify")
+        << "non-clausal constant propagation : " << cProp << std::endl;
+  }
+
+  // Add new substitutions to topLevelSubstitutions
+  // Note that we don't have to keep rhs's in full solved form
+  // because SubstitutionMap::apply does a fixed-point iteration when
+  // substituting
+  top_level_substs.addSubstitutions(newSubstitutions);
+
+  if (learnedBuilder.getNumChildren() > 1)
+  {
+    assertionsToPreprocess->replace(
+        assertionsToPreprocess->getRealAssertionsEnd() - 1,
+        Rewriter::rewrite(Node(learnedBuilder)));
+  }
+
+  propagator->setNeedsFinish(true);
+  return PreprocessingPassResult::NO_CONFLICT;
+}  // namespace passes
+
+/* -------------------------------------------------------------------------- */
+
+}  // namespace passes
+}  // namespace preprocessing
+}  // namespace CVC4