pow2: header file for pow2 solver (#6676)

This PR adds a header file for the pow2 solver. It also includes an empty test file, to trigger compilation of the header file. The next PR will include implementations and tests.

2 files changed, 110 insertions, 0 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 5faeddbed..775e04b9c 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -437,6 +437,7 @@ libcvc5_add_sources(
   theory/arith/nl/nonlinear_extension.h
   theory/arith/nl/poly_conversion.cpp
   theory/arith/nl/poly_conversion.h
+  theory/arith/nl/pow2_solver.h
   theory/arith/nl/stats.cpp
   theory/arith/nl/stats.h
   theory/arith/nl/strategy.cpp
diff --git a/src/theory/arith/nl/pow2_solver.h b/src/theory/arith/nl/pow2_solver.h
new file mode 100644
index 000000000..4796b2147
--- /dev/null
+++ b/src/theory/arith/nl/pow2_solver.h
@@ -0,0 +1,109 @@
+/******************************************************************************
+ * Top contributors (to current version):
+ *   Yoni Zohar
+ *
+ * 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.
+ * ****************************************************************************
+ *
+ * Solver for pow2 constraints.
+ */
+
+#ifndef CVC5__THEORY__ARITH__NL__POW2_SOLVER_H
+#define CVC5__THEORY__ARITH__NL__POW2_SOLVER_H
+
+#include <vector>
+
+#include "context/cdhashset.h"
+#include "expr/node.h"
+
+namespace cvc5 {
+namespace theory {
+namespace arith {
+
+class ArithState;
+class InferenceManager;
+
+namespace nl {
+
+class NlModel;
+
+/** pow2 solver class
+ *
+ */
+class Pow2Solver
+{
+  using NodeSet = context::CDHashSet<Node>;
+
+ public:
+  Pow2Solver(InferenceManager& im, ArithState& state, NlModel& model);
+  ~Pow2Solver();
+
+  /** init last call
+   *
+   * This is called at the beginning of last call effort check, where
+   * assertions are the set of assertions belonging to arithmetic,
+   * false_asserts is the subset of assertions that are false in the current
+   * model, and xts is the set of extended function terms that are active in
+   * the current context.
+   */
+  void initLastCall(const std::vector<Node>& assertions,
+                    const std::vector<Node>& false_asserts,
+                    const std::vector<Node>& xts);
+  //-------------------------------------------- lemma schemas
+  /** check initial refine
+   *
+   * Returns a set of valid theory lemmas, based on simple facts about pow2.
+   *
+   * Examples
+   *
+   * x>=0 --> x < pow2(x)
+   *
+   * This should be a heuristic incomplete check that only introduces a
+   * small number of new terms in the lemmas it returns.
+   */
+  void checkInitialRefine();
+  /** check full refine
+   *
+   * This should be a complete check that returns at least one lemma to
+   * rule out the current model.
+   */
+  void checkFullRefine();
+
+  //-------------------------------------------- end lemma schemas
+ private:
+  // The inference manager that we push conflicts and lemmas to.
+  InferenceManager& d_im;
+  /** Reference to the non-linear model object */
+  NlModel& d_model;
+  /** commonly used terms */
+  Node d_false;
+  Node d_true;
+  Node d_zero;
+  Node d_one;
+  Node d_two;
+
+  NodeSet d_initRefine;
+  /** all pow2 terms 
+   * Cleared at each last call effort check. 
+   * */
+  std::vector<Node> d_pow2s;
+
+  /**
+   * Value-based refinement lemma for i of the form (pow2 x). Returns:
+   *   x = M(x) /\ x>= 0 ---->
+   *     (pow2 x) = Rewriter::rewrite((pow2 M(x)))
+   */
+  Node valueBasedLemma(Node i);
+}; /* class Pow2Solver */
+
+}  // namespace nl
+}  // namespace arith
+}  // namespace theory
+}  // namespace cvc5
+
+#endif /* CVC5__THEORY__ARITH__POW2_SOLVER_H */