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diff --git a/src/theory/difficulty_manager.h b/src/theory/difficulty_manager.h
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+/******************************************************************************
+ * 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 */