add ovfl constraint

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

src/math/polysat/mul_ovfl_constraint.cpp

@@ -0,0 +1,95 @@
+/*++
+Copyright (c) 2021 Microsoft Corporation
+
+Module Name:
+
+    polysat multiplication overflow constraint
+
+Author:
+
+    Jakob Rath, Nikolaj Bjorner (nbjorner) 2021-12-09
+
+--*/
+#pragma once
+#include "math/polysat/mul_ovfl_constraint.h"
+
+namespace polysat {
+
+
+    mul_ovfl_constraint::mul_ovfl_constraint(constraint_manager& m, pdd const& p, pdd const& q):
+        constraint(m, ckind_t::mul_ovfl_t), m_p(p), m_q(q) {
+
+        simplify();
+        m_vars.append(m_p.free_vars());
+        for (auto v : m_q.free_vars())
+            if (!m_vars.contains(v))
+                m_vars.push_back(v);
+
+    }
+    void mul_ovfl_constraint::simplify() {
+        if (m_p.is_zero() || m_q.is_zero() ||
+            m_p.is_one() || m_q.is_one()) {
+            m_q = 0;
+            m_p = 0;
+            return;
+        }
+    }
+
+    std::ostream& mul_ovfl_constraint::display(std::ostream& out, lbool status) const {
+        switch (status) {
+        case l_true: return display(out);
+        case l_false: return display(out << "~");
+        case l_undef: return display(out << "?");
+        }       
+    }
+
+    std::ostream& mul_ovfl_constraint::display(std::ostream& out) const {
+        return "ovfl*(" << m_p << ", " << m_q << ")";       
+    }
+
+
+    bool mul_ovfl_constraint::is_always_false(bool is_positive, pdd const& p, pdd const& q) const {
+        if (!is_positive && (p.is_zero() || q.is_zero() ||
+            p.is_one() || q.is_one()))
+            return true;
+        if (p.is_val() && q.is_val()) {
+            bool ovfl = p.val() * q.val() > p().manager().max_value();
+            return is_positive == ovfl;
+        }
+        return false;
+    }
+
+    bool mul_ovfl_constraint::is_always_false(bool is_positive) const {
+        return is_always_false(is_positive, m_p, m_q);
+    }
+
+    bool mul_ovfl_constraint::is_currently_false(assignment_t const& a, bool is_positive) const {
+        auto p = p().subst_val(s.assignment());
+        auto q = q().subst_val(s.assignment());
+        return is_always_false(is_positive, p, q);
+    }
+
+    bool mul_ovfl_constraint::is_currently_true(assignment_t const& a, bool is_positive) const {
+        return !is_currently_false(a, !is_positive);
+    }
+
+    void mul_ovfl_constraint::narrow(solver& s, bool is_positive) {    
+        auto p = p().subst_val(s.assignment());
+        auto q = q().subst_val(s.assignment());
+
+        if (is_always_false(is_positive, p, q)) {
+            s.set_conflict({ this, is_positive });
+            return;
+        }
+
+        NOT_IMPLEMENTED_YET();
+    }
+
+    unsigned mul_ovfl_constraint::hash() const {
+    	return mk_mix(p().hash(), q().hash(), 25);
+    }
+
+    bool mul_ovfl_constraint::operator==(constraint const& other) const {
+        return other.is_mul_ovfl() && p() == other.to_mul_ovfl().p() && q() == other.to_mul_ovfl().q();
+    }
+}