delay internalization, relevancy (#4707)

* delay evaluation

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

* Update bv_solver.cpp

* delay internalize

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

* compiler warnings

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

* remove gc

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

* add bv delay option

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/sat/smt/sat_dual_solver.h

@@ -0,0 +1,64 @@
+/*++
+Copyright (c) 2020 Microsoft Corporation
+
+Module Name:
+
+    sat_dual_solver.h
+
+Abstract:
+
+    Solver for obtaining implicant.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2020-08-25
+
+--*/
+#pragma once
+#include "sat/sat_solver.h"
+
+namespace sat {
+
+    class dual_solver {
+        solver          m_solver;
+        literal_vector  m_roots, m_lits, m_core;
+        bool_var_vector m_is_tracked;
+        unsigned_vector m_tracked_stack;
+        unsigned_vector m_ext2var;
+        unsigned_vector m_var2ext;
+        unsigned_vector m_roots_lim, m_tracked_lim;
+        void add_literal(literal lit);
+
+        bool_var ext2var(bool_var v);
+        bool_var var2ext(bool_var v);
+        literal  ext2lit(literal lit);
+        literal  lit2ext(literal lit);
+    public:
+        dual_solver(reslimit& l);
+        void push();
+        void pop(unsigned num_scopes);
+
+        /*
+        * track model relevancy for variable 
+        */
+        void track_relevancy(bool_var v);
+
+        /*
+        * Add a root clause from the input problem.
+        * At least one literal has to be satisfied in every root.
+        */
+        void add_root(literal lit, unsigned sz, literal const* clause);
+
+        /*
+        * Add auxiliary clauses that originate from compiling definitions.
+        */
+        void add_aux(unsigned sz, literal const* clause);
+
+        /*
+        * Extract a minimized subset of relevant literals from a model for s.
+        */
+        bool operator()(solver const& s);
+
+        literal_vector const& core() const { return m_core; }
+    };
+}