Implement iteration_cb for LearningSolver; reactivate TSP

miplearn/solvers/internal.py

@@ -126,7 +126,7 @@ class InternalSolver(ABC):
 
         Parameters
         ----------
-        iteration_cb: function
+        iteration_cb: () -> Bool
             By default, InternalSolver makes a single call to the native `solve`
             method and returns the result. If an iteration callback is provided
             instead, InternalSolver enters a loop, where `solve` and `iteration_cb`

miplearn/solvers/learning.py

@@ -171,8 +171,15 @@ class LearningSolver:
         if relaxation_only:
             return results
 
+        def iteration_cb():
+            should_repeat = False
+            for component in self.components.values():
+                if component.after_iteration(self, instance, model):
+                    should_repeat = True
+            return should_repeat
+
         logger.info("Solving MILP...")
-        results = self.internal_solver.solve(tee=tee)
+        results = self.internal_solver.solve(tee=tee, iteration_cb=iteration_cb)
         results["LP value"] = instance.lp_value
 
         # Read MIP solution and bounds

miplearn/solvers/tests/test_learning_solver.py

@@ -64,4 +64,4 @@ def test_add_components():
     solver.add(DynamicLazyConstraintsComponent())
     solver.add(DynamicLazyConstraintsComponent())
     assert len(solver.components) == 1
-    assert "LazyConstraintsComponent" in solver.components
+    assert "DynamicLazyConstraintsComponent" in solver.components