Add difficulty manager (#7151)

Towards supporting a (get-difficulty) command.

This tracks an estimate of the difficulty of preprocessed assertions during solving. It will be connected to TheoryEngine (via RelevanceManager) in a followup PR.

4 files changed, 209 insertions, 0 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 401fc5976..ecfef1c22 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -690,6 +690,8 @@ libcvc5_add_sources(
   theory/decision_manager.h
   theory/decision_strategy.cpp
   theory/decision_strategy.h
+  theory/difficulty_manager.cpp
+  theory/difficulty_manager.h
   theory/ee_manager.cpp
   theory/ee_manager.h
   theory/ee_manager_central.cpp
diff --git a/src/options/smt_options.toml b/src/options/smt_options.toml
index 40a37fa7b..7d0dab720 100644
--- a/src/options/smt_options.toml
+++ b/src/options/smt_options.toml
@@ -221,6 +221,21 @@ name   = "SMT Layer"
   help       = "turn on unsat assumptions generation"
 
 [[option]]
+  name       = "difficultyMode"
+  category   = "regular"
+  long       = "difficulty-mode=MODE"
+  type       = "DifficultyMode"
+  default    = "LEMMA_LITERAL"
+  help       = "choose output mode for get-difficulty, see --difficulty-mode=help"
+  help_mode  = "difficulty output modes."
+[[option.mode.LEMMA_LITERAL]]
+  name = "lemma-literal"
+  help = "Difficulty of an assertion is how many lemmas use a literal that the assertion depends on to be satisfied."
+[[option.mode.MODEL_CHECK]]
+  name = "model-check"
+  help = "Difficulty of an assertion is how many times it was not satisfied in a candidate model."
+
+[[option]]
   name       = "checkSynthSol"
   category   = "regular"
   long       = "check-synth-sol"
diff --git a/src/theory/difficulty_manager.cpp b/src/theory/difficulty_manager.cpp
new file mode 100644
index 000000000..3df86383f
--- /dev/null
+++ b/src/theory/difficulty_manager.cpp
@@ -0,0 +1,109 @@
+/******************************************************************************
+ * Top contributors (to current version):
+ *   Andrew Reynolds
+ *
+ * This file is part of the cvc5 project.
+ *
+ * Copyright (c) 2009-2021 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.
+ * ****************************************************************************
+ *
+ * Difficulty manager.
+ */
+
+#include "theory/difficulty_manager.h"
+
+#include "options/smt_options.h"
+#include "smt/env.h"
+#include "theory/theory_model.h"
+#include "util/rational.h"
+
+namespace cvc5 {
+namespace theory {
+
+DifficultyManager::DifficultyManager(context::Context* c, Valuation val)
+    : d_val(val), d_dfmap(c)
+{
+}
+
+void DifficultyManager::getDifficultyMap(std::map<Node, Node>& dmap)
+{
+  NodeManager* nm = NodeManager::currentNM();
+  for (const std::pair<const Node, uint64_t> p : d_dfmap)
+  {
+    dmap[p.first] = nm->mkConst(Rational(p.second));
+  }
+}
+
+void DifficultyManager::notifyLemma(const std::map<TNode, TNode>& rse, Node n)
+{
+  if (options::difficultyMode() != options::DifficultyMode::LEMMA_LITERAL)
+  {
+    return;
+  }
+  Trace("diff-man") << "notifyLemma: " << n << std::endl;
+  Kind nk = n.getKind();
+  // for lemma (or a_1 ... a_n), if a_i is a literal that is not true in the
+  // valuation, then we increment the difficulty of that assertion
+  std::vector<TNode> litsToCheck;
+  if (nk == kind::OR)
+  {
+    litsToCheck.insert(litsToCheck.end(), n.begin(), n.end());
+  }
+  else if (nk == kind::IMPLIES)
+  {
+    litsToCheck.push_back(n[0].negate());
+    litsToCheck.push_back(n[1]);
+  }
+  else
+  {
+    litsToCheck.push_back(n);
+  }
+  std::map<TNode, TNode>::const_iterator it;
+  for (TNode nc : litsToCheck)
+  {
+    bool pol = nc.getKind() != kind::NOT;
+    TNode atom = pol ? nc : nc[0];
+    it = rse.find(atom);
+    if (it != rse.end())
+    {
+      incrementDifficulty(it->second);
+    }
+  }
+}
+
+void DifficultyManager::notifyCandidateModel(const NodeList& input,
+                                             TheoryModel* m)
+{
+  if (options::difficultyMode() != options::DifficultyMode::MODEL_CHECK)
+  {
+    return;
+  }
+  Trace("diff-man") << "DifficultyManager::notifyCandidateModel, #input="
+                    << input.size() << std::endl;
+  for (const Node& a : input)
+  {
+    // should have miniscoped the assertions upstream
+    Assert(a.getKind() != kind::AND);
+    // check if each input is satisfied
+    Node av = m->getValue(a);
+    if (av.isConst() && av.getConst<bool>())
+    {
+      continue;
+    }
+    Trace("diff-man") << "  not true: " << a << std::endl;
+    // not satisfied, increment counter
+    incrementDifficulty(a);
+  }
+  Trace("diff-man") << std::endl;
+}
+void DifficultyManager::incrementDifficulty(TNode a, uint64_t amount)
+{
+  Assert(a.getType().isBoolean());
+  d_dfmap[a] = d_dfmap[a] + amount;
+}
+
+}  // namespace theory
+}  // namespace cvc5
diff --git a/src/theory/difficulty_manager.h b/src/theory/difficulty_manager.h
new file mode 100644
index 000000000..3030bcc9b
--- /dev/null
+++ b/src/theory/difficulty_manager.h
@@ -0,0 +1,83 @@
+/******************************************************************************
+ * Top contributors (to current version):
+ *   Andrew Reynolds
+ *
+ * This file is part of the cvc5 project.
+ *
+ * Copyright (c) 2009-2021 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.
+ * ****************************************************************************
+ *
+ * Relevance manager.
+ */
+
+#include "cvc5_private.h"
+
+#ifndef CVC5__THEORY__DIFFICULTY_MANAGER__H
+#define CVC5__THEORY__DIFFICULTY_MANAGER__H
+
+#include "context/cdhashmap.h"
+#include "context/cdlist.h"
+#include "expr/node.h"
+#include "theory/valuation.h"
+
+namespace cvc5 {
+namespace theory {
+
+class TheoryModel;
+
+/**
+ * Difficulty manager, which tracks an estimate of the difficulty of each
+ * preprocessed assertion during solving.
+ */
+class DifficultyManager
+{
+  typedef context::CDList<Node> NodeList;
+  typedef context::CDHashMap<Node, uint64_t> NodeUIntMap;
+
+ public:
+  DifficultyManager(context::Context* c, Valuation val);
+  /**
+   * Get difficulty map, which populates dmap mapping preprocessed assertions
+   * to a difficulty measure (a constant integer).
+   */
+  void getDifficultyMap(std::map<Node, Node>& dmap);
+  /**
+   * Notify lemma, for difficulty measurements. This increments the difficulty
+   * of assertions that share literals with that lemma if the difficulty mode
+   * is LEMMA_LITERAL. In particular, for each literal lit in the lemma lem, we
+   * increment the difficulty of the assertion res[lit], which corresponds to
+   * the assertion that was the reason why the literal is relevant in the
+   * current context.
+   *
+   * @param rse Mapping from literals to the preprocessed assertion that was
+   * the reason why that literal was relevant in the current context
+   * @param lem The lemma
+   */
+  void notifyLemma(const std::map<TNode, TNode>& rse, Node lem);
+  /**
+   * Notify that `m` is a (candidate) model. This increments the difficulty
+   * of assertions that are not satisfied by that model.
+   *
+   * @param input The list of preprocessed assertions
+   * @param m The candidate model.
+   */
+  void notifyCandidateModel(const NodeList& input, TheoryModel* m);
+
+ private:
+  /** Increment difficulty on assertion a */
+  void incrementDifficulty(TNode a, uint64_t amount = 1);
+  /** The valuation object, used to query current value of theory literals */
+  Valuation d_val;
+  /**
+   * User-context dependent mapping from input assertions to difficulty measure
+   */
+  NodeUIntMap d_dfmap;
+};
+
+}  // namespace theory
+}  // namespace cvc5
+
+#endif /* CVC5__THEORY__DIFFICULTY_MANAGER__H */