Merge pull request #3241 from emma58/fix-domain-bug-in-var-aggregator

contrib.preprocessing: Fixing bug where variable aggregator did not intersect domains

Author: emma58

pyomo/contrib/preprocessing/plugins/var_aggregator.py

@@ -13,7 +13,14 @@
 
 
 from pyomo.common.collections import ComponentMap, ComponentSet
-from pyomo.core.base import Block, Constraint, VarList, Objective, TransformationFactory
+from pyomo.core.base import (
+    Block,
+    Constraint,
+    VarList,
+    Objective,
+    Reals,
+    TransformationFactory,
+)
 from pyomo.core.expr import ExpressionReplacementVisitor
 from pyomo.core.expr.numvalue import value
 from pyomo.core.plugins.transform.hierarchy import IsomorphicTransformation
@@ -248,6 +255,12 @@ def _apply_to(self, model, detect_fixed_vars=True):
             # the variables in its equality set.
             z_agg.setlb(max_if_not_None(v.lb for v in eq_set if v.has_lb()))
             z_agg.setub(min_if_not_None(v.ub for v in eq_set if v.has_ub()))
+            # Set the domain of the aggregate variable to the intersection of
+            # the domains of the variables in its equality set
+            domain = Reals
+            for v in eq_set:
+                domain = domain & v.domain
+            z_agg.domain = domain
 
             # Set the fixed status of the aggregate var
             fixed_vars = [v for v in eq_set if v.fixed]

pyomo/contrib/preprocessing/tests/test_var_aggregator.py

@@ -19,12 +19,16 @@
     max_if_not_None,
     min_if_not_None,
 )
+from pyomo.core.expr.compare import assertExpressionsEqual
 from pyomo.environ import (
+    Binary,
     ConcreteModel,
     Constraint,
     ConstraintList,
+    maximize,
     Objective,
     RangeSet,
+    Reals,
     SolverFactory,
     TransformationFactory,
     Var,
@@ -210,6 +214,36 @@ def test_var_update(self):
         self.assertEqual(m.x.value, 0)
         self.assertEqual(m.y.value, 0)
 
+    def test_binary_inequality(self):
+        m = ConcreteModel()
+        m.x = Var(domain=Binary)
+        m.y = Var(domain=Binary)
+        m.c = Constraint(expr=m.x == m.y)
+        m.o = Objective(expr=0.5 * m.x + m.y, sense=maximize)
+        TransformationFactory('contrib.aggregate_vars').apply_to(m)
+        var_to_z = m._var_aggregator_info.var_to_z
+        z = var_to_z[m.x]
+        self.assertIs(var_to_z[m.y], z)
+        self.assertEqual(z.domain, Binary)
+        self.assertEqual(z.lb, 0)
+        self.assertEqual(z.ub, 1)
+        assertExpressionsEqual(self, m.o.expr, 0.5 * z + z)
+
+    def test_equality_different_domains(self):
+        m = ConcreteModel()
+        m.x = Var(domain=Reals, bounds=(1, 2))
+        m.y = Var(domain=Binary)
+        m.c = Constraint(expr=m.x == m.y)
+        m.o = Objective(expr=0.5 * m.x + m.y, sense=maximize)
+        TransformationFactory('contrib.aggregate_vars').apply_to(m)
+        var_to_z = m._var_aggregator_info.var_to_z
+        z = var_to_z[m.x]
+        self.assertIs(var_to_z[m.y], z)
+        self.assertEqual(z.lb, 1)
+        self.assertEqual(z.ub, 1)
+        self.assertEqual(z.domain, Binary)
+        assertExpressionsEqual(self, m.o.expr, 0.5 * z + z)
+
 
 if __name__ == '__main__':
     unittest.main()