Merge pull request #201 from pathsim/fix/remove-connection-zero-inputs

milanofthe · web-flow · commit b84bfda902ca · 2026-02-19T16:02:51.000+01:00
remove connection zero inputs
diff --git a/src/pathsim/simulation.py b/src/pathsim/simulation.py
@@ -499,10 +499,14 @@ def remove_event(self, event):
     # system assembly -------------------------------------------------------------
 
     def _assemble_graph(self):
-        """Build the internal graph representation for fast system function 
+        """Build the internal graph representation for fast system function
         evaluation and algebraic loop resolution.
         """
 
+        #reset all block inputs to clear stale values from removed connections
+        for block in self.blocks:
+            block.inputs.reset()
+
         #time the graph construction
         with Timer(verbose=False) as T:
             self.graph = Graph(self.blocks, self.connections)
diff --git a/src/pathsim/subsystem.py b/src/pathsim/subsystem.py
@@ -381,6 +381,11 @@ def _assemble_graph(self):
         """Assemble internal graph of subsystem for fast
         algebraic evaluation during simulation.
         """
+
+        #reset all block inputs to clear stale values from removed connections
+        for block in self.blocks:
+            block.inputs.reset()
+
         self.graph = Graph({*self.blocks, self.interface}, self.connections)
         self._graph_dirty = False
 
diff --git a/tests/pathsim/test_simulation.py b/tests/pathsim/test_simulation.py
@@ -884,6 +884,23 @@ def test_remove_connection_error(self):
         with self.assertRaises(ValueError):
             self.Sim.remove_connection(C)
 
+    def test_remove_connection_zeroes_inputs(self):
+        """Removing a connection zeroes target inputs on next graph rebuild"""
+        # Run a step so the connection pushes data
+        self.Src.function = lambda t: 5.0
+        self.Sim.step(0.01)
+
+        # Int should have received input from Src
+        self.assertNotEqual(self.Int.inputs[0], 0.0)
+
+        # Remove the connection — graph is dirty but not rebuilt yet
+        self.Sim.remove_connection(self.C1)
+        self.assertTrue(self.Sim._graph_dirty)
+
+        # Next step triggers graph rebuild which resets inputs
+        self.Sim.step(0.01)
+        self.assertEqual(self.Int.inputs[0], 0.0)
+
     def test_remove_event(self):
         """Adding and removing events works"""
         evt = Event(func_evt=lambda t: t - 1.0, func_act=lambda t: None)
