Merge pull request #2850 from emma58/logical-to-disjunctive-bugfix

contrib.cp: Fixing a bug where the logical-to-disjunctive walker ignored fixedness of BooleanVars

pyomo/contrib/cp/tests/test_logical_to_disjunctive.py

@@ -283,6 +283,86 @@ def test_at_least(self):
             self, m.cons[1].expr, m.disjuncts[0].binary_indicator_var >= 1
         )
 
+    def test_boolean_fixed_true(self):
+        m = self.make_model()
+        e = m.a.implies(m.b)
+        m.a.fix(True)
+
+        visitor = LogicalToDisjunctiveVisitor()
+        m.cons = visitor.constraints
+        m.z = visitor.z_vars
+        m.disjuncts = visitor.disjuncts
+        m.disjunctions = visitor.disjunctions
+
+        visitor.walk_expression(e)
+        # we'll get !a v b
+        self.assertEqual(len(m.z), 3)
+        self.assertEqual(len(m.cons), 4)
+
+        self.assertIs(m.a.get_associated_binary(), m.z[1])
+        self.assertTrue(m.z[1].fixed)
+        self.assertEqual(value(m.z[1]), 1)
+        self.assertIs(m.b.get_associated_binary(), m.z[2])
+
+        assertExpressionsEqual(
+            self, m.cons[1].expr, (1 - m.z[3]) + (1 - m.z[1]) + m.z[2] >= 1
+        )
+        assertExpressionsEqual(self, m.cons[2].expr, 1 - (1 - m.z[1]) + m.z[3] >= 1)
+        assertExpressionsEqual(self, m.cons[3].expr, m.z[3] + (1 - m.z[2]) >= 1)
+        assertExpressionsEqual(self, m.cons[4].expr, m.z[3] >= 1)
+
+    def test_boolean_fixed_false(self):
+        m = self.make_model()
+        e = m.a & m.b
+        m.a.fix(False)
+
+        visitor = LogicalToDisjunctiveVisitor()
+        m.cons = visitor.constraints
+        m.z = visitor.z_vars
+        m.disjuncts = visitor.disjuncts
+        m.disjunctions = visitor.disjunctions
+
+        visitor.walk_expression(e)
+        # we'll get !a v b
+        self.assertEqual(len(m.z), 3)
+        self.assertEqual(len(m.cons), 3)
+
+        self.assertIs(m.a.get_associated_binary(), m.z[1])
+        self.assertTrue(m.z[1].fixed)
+        self.assertEqual(value(m.z[1]), 0)
+        self.assertIs(m.b.get_associated_binary(), m.z[2])
+
+        assertExpressionsEqual(self, m.cons[1].expr, m.z[1] >= m.z[3])
+        assertExpressionsEqual(self, m.cons[2].expr, m.z[2] >= m.z[3])
+        assertExpressionsEqual(self, m.cons[3].expr, m.z[3] >= 1)
+
+    def test_boolean_fixed_none(self):
+        m = self.make_model()
+        e = m.a & m.b
+        # I don't get what this means, but you can do it, so... I guess we need
+        # to handle it.
+        m.a.fix(None)
+
+        visitor = LogicalToDisjunctiveVisitor()
+        m.cons = visitor.constraints
+        m.z = visitor.z_vars
+        m.disjuncts = visitor.disjuncts
+        m.disjunctions = visitor.disjunctions
+
+        visitor.walk_expression(e)
+        # we'll get !a v b
+        self.assertEqual(len(m.z), 3)
+        self.assertEqual(len(m.cons), 3)
+
+        self.assertIs(m.a.get_associated_binary(), m.z[1])
+        self.assertTrue(m.z[1].fixed)
+        self.assertIsNone(m.z[1].value)
+        self.assertIs(m.b.get_associated_binary(), m.z[2])
+
+        assertExpressionsEqual(self, m.cons[1].expr, m.z[1] >= m.z[3])
+        assertExpressionsEqual(self, m.cons[2].expr, m.z[2] >= m.z[3])
+        assertExpressionsEqual(self, m.cons[3].expr, m.z[3] >= 1)
+
     def test_no_need_to_walk(self):
         m = self.make_model()
         e = m.a

pyomo/contrib/cp/transform/logical_to_disjunctive_walker.py

@@ -43,6 +43,11 @@ def _dispatch_boolean_var(visitor, node):
             z = visitor.z_vars.add()
             visitor.boolean_to_binary_map[node] = z
             node.associate_binary_var(z)
+    if node.fixed:
+        visitor.boolean_to_binary_map[node].fixed = True
+        visitor.boolean_to_binary_map[node].set_value(
+            int(node.value) if node.value is not None else None, skip_validation=True
+        )
     return False, visitor.boolean_to_binary_map[node]