sketch mbi

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

src/qe/qe_mbi.h

@@ -0,0 +1,90 @@
+/*++
+Copyright (c) 2018 Microsoft Corporation
+
+Module Name:
+
+    qe_mbi.h
+
+Abstract:
+
+    Model-based interpolation utilities
+
+Author:
+
+    Nikolaj Bjorner (nbjorner), Arie Gurfinkel 2018-6-8
+
+Revision History:
+
+
+--*/
+
+#pragma once
+
+namespace qe {
+    enum mbi_result {
+        mbi_sat,
+        mbi_unsat,
+        mbi_augment,
+        mbi_undef,
+    };
+
+    class mbi_plugin {
+        virtual ~mbi_plugin();
+        /**
+         * \brief Utility that works modulo a background state.
+         * - vars
+         *   variables to preferrably project onto (other variables would require quantification to fit interpolation signature)
+         * - lits 
+         *   set of literals to check satisfiability with respect to.
+         * - mdl
+         *   optional model for caller. 
+         * on return:
+         * - mbi_sat:
+         *   populates mdl with a satisfying state, and lits with implicant for background state.
+         * - mbi_unsat:
+         *   populates lits to be inconsistent with background state. 
+         *   For all practical purposes it is a weakening of lits or even a subset of lits.
+         * - mbi_augment:
+         *   populates lits with strengthening of lits (superset) 
+         * - mbi_undef:
+         *   inconclusive, 
+         */
+        virtual mbi_result operator()(func_decl_ref_vector const& vars, expr_ref_vector& lits, model_ref& mdl) = 0;
+
+        /**
+         * \brief Block conjunction of lits from future mbi_augment or mbi_sat.
+         */
+        virtual void block(expr_ref_vector const& lits) = 0;
+    };
+
+    class euf_mbi_plugin : mbi_plugin {
+        solver_ref m_solver;
+    public:
+        euf_mbi_plugin(solver* s);
+        ~euf_mbi_plugin() override {}
+        mbi_result operator()(func_decl_ref_vector const& vars, expr_ref_vector& lits, model_ref& mdl) override;
+        void block(expr_ref_vector const& lits) override;
+    };
+
+    /**
+     * use cases for interpolation.
+     */
+    class interpolator {
+        static lbool binary(mbi_plugin& a, mbi_plugin& b, func_decl_ref_vector const& vars, expr_ref& itp);
+    };
+
+#if 0
+    TBD some other scenario, e.g., Farkas, Cute/Beautiful/maybe even Selfless
+
+    class solver_mbi_plugin : public mbi_plugin {
+        solver_ref m_solver;
+    public:
+        solver_mbi_plugin(solver* s);
+        ~solver_mbi_plugin() override {}
+        mbi_result operator()(func_decl_ref_vector const& vars, expr_ref_vector& lits, model_ref& mdl) override;
+        void block(expr_ref_vector const& lits) override;
+    };
+
+
+#endif
+};