Temporarily remove native solver callbacks; add iteration_cb

miplearn/solvers/tests/test_internal_solver.py

@@ -6,10 +6,9 @@ import logging
 from io import StringIO
 
 import pyomo.environ as pe
-from miplearn import BasePyomoSolver
-from miplearn.problems.knapsack import ChallengeA
-from miplearn.solvers import RedirectOutput
 
+from miplearn import BasePyomoSolver, GurobiSolver
+from miplearn.solvers import RedirectOutput
 from . import _get_instance, _get_internal_solvers
 
 logger = logging.getLogger(__name__)
@@ -99,17 +98,59 @@ def test_internal_solver():
         assert solution["x"][2] == 1.0
         assert solution["x"][3] == 1.0
 
+        # Add a brand new constraint
         if isinstance(solver, BasePyomoSolver):
-            model.cut = pe.Constraint(expr=model.x[0] <= 0.5)
+            model.cut = pe.Constraint(expr=model.x[0] <= 0.0, name="cut")
             solver.add_constraint(model.cut)
-            solver.solve_lp()
-            assert model.x[0].value == 0.5
+        elif isinstance(solver, GurobiSolver):
+            x = model.getVarByName("x[0]")
+            solver.add_constraint(x <= 0.0, name="cut")
+        else:
+            raise Exception("Illegal state")
+
+        # New constraint should affect solution and should be listed in
+        # constraint ids
+        assert solver.get_constraints_ids() == ["eq_capacity", "cut"]
+        stats = solver.solve()
+        assert stats["Lower bound"] == 1030.0
+
+        if isinstance(solver, GurobiSolver):
+            # Extract new constraint
+            cobj = solver.extract_constraint("cut")
+
+            # New constraint should no longer affect solution and should no longer
+            # be listed in constraint ids
+            assert solver.get_constraints_ids() == ["eq_capacity"]
+            stats = solver.solve()
+            assert stats["Lower bound"] == 1183.0
+
+            # New constraint should not be satisfied by current solution
+            assert not solver.is_constraint_satisfied(cobj)
+
+            # Re-add constraint
+            solver.add_constraint(cobj)
+
+            # Constraint should affect solution again
+            assert solver.get_constraints_ids() == ["eq_capacity", "cut"]
+            stats = solver.solve()
+            assert stats["Lower bound"] == 1030.0
+
+            # New constraint should now be satisfied
+            assert solver.is_constraint_satisfied(cobj)
 
 
-# def test_node_count():
-#     for solver in _get_internal_solvers():
-#         challenge = ChallengeA()
-#         solver.set_time_limit(1)
-#         solver.set_instance(challenge.test_instances[0])
-#         stats = solver.solve(tee=True)
-#         assert stats["Nodes"] > 1
+def test_iteration_cb():
+    for solver_class in _get_internal_solvers():
+        logger.info("Solver: %s" % solver_class)
+        instance = _get_instance(solver_class)
+        solver = solver_class()
+        solver.set_instance(instance)
+        count = 0
+
+        def custom_iteration_cb():
+            nonlocal count
+            count += 1
+            return count < 5
+
+        solver.solve(iteration_cb=custom_iteration_cb)
+        assert count == 5