moving out viable functionality

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

src/math/polysat/viable.h

@@ -0,0 +1,91 @@
+/*++
+Copyright (c) 2021 Microsoft Corporation
+
+Module Name:
+
+    maintain viable domains
+
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2021-03-19
+    Jakob Rath 2021-04-6
+
+--*/
+#pragma once
+
+#include <limits>
+#include "math/dd/dd_bdd.h"
+#include "math/polysat/types.h"
+
+namespace polysat {
+
+    class solver;
+
+    class viable {
+        typedef dd::bdd bdd;
+        solver& s;
+        dd::bdd_manager              m_bdd;
+        scoped_ptr_vector<dd::fdd>   m_bits;
+        vector<bdd>                  m_viable;   // set of viable values.
+        vector<std::pair<pvar, bdd>> m_viable_trail;
+
+    public:
+        viable(solver& s);
+
+        void push() { m_viable.push_back(m_bdd.mk_true()); }
+        void pop() { m_viable.pop_back(); }
+
+        void push_viable(pvar v);
+
+        void pop_viable();
+
+        void intersect_eq(rational const& a, pvar v, rational const& b, bool is_positive);
+
+        /**
+         * Check whether variable v has any viable values left according to m_viable.
+         */
+        bool has_viable(pvar v);
+
+        bool is_false(pvar v) { return m_viable[v].is_false(); }
+
+        /**
+         * check if value is viable according to m_viable.
+         */
+        bool is_viable(pvar v, rational const& val);
+
+        /**
+         * register that val is non-viable for var.
+         */
+        void add_non_viable(pvar v, rational const& val);
+
+        /**
+         * Register all values that are not contained in vals as non-viable.
+         */
+        void intersect_viable(pvar v, bdd vals);
+
+        /**
+         * Add dependency for variable viable range.
+         */
+        void add_viable_dep(pvar v, p_dependency* dep);
+
+        /**
+         * Find a next viable value for variable.
+         */
+        dd::find_t find_viable(pvar v, rational & val);
+
+        /** Log all viable values for the given variable.
+         * (Inefficient, but useful for debugging small instances.)
+         */
+        void log(pvar v);
+        /** Like log_viable but for all variables */
+        void log();
+
+        dd::bdd_manager& get_bdd() { return m_bdd; }
+        dd::fdd const& sz2bits(unsigned sz);
+        dd::fdd const& var2bits(pvar v);
+
+    };
+}
+
+