fix: fixing a bug for the Master algorithm where connections could be…

CHANGELOG

@@ -2,6 +2,8 @@
 --- PyFMI-FUTURE ---
     * Fixed a crash with the `Master` algorithm option `block_initialization`.
     * Fixed a result handling issue for `dynamic_diagnostics = True` and `["<solver>_options"]["clock_step"] = False`.
+    * Fixed an issue for the `Master` algorithm where connection values could be initialized incorrectly, when FMUs 
+      were initialized separately and using `step_size_downsampling_factor`.
 
 --- PyFMI-2.20.1 ---
     * Resolved issue where caching in result handling was too persistent and could prevent automatic garbage collection.

src/pyfmi/master.pyx

@@ -1253,10 +1253,6 @@ cdef class Master:
 
         exit_initialization_mode(self.models, self.elapsed_time_init)
 
-        #Store the outputs
-        self.y_prev = self.get_connection_outputs(initialize = True).copy()
-        self.set_last_y(self.y_prev)
-
     def initialize_result_objects(self, opts):
         if (opts["result_handling"] == "custom") and (not isinstance(opts["result_handler"], dict)):
             raise FMUException("'result_handler' option must be a dictionary for 'result_handling' = 'custom'.")
@@ -1666,8 +1662,13 @@ cdef class Master:
             time_stop  = timer()
             print('Elapsed initialization time: ' + str(time_stop-time_start) + ' seconds.')
 
+        # Get outputs and update previous values
+        self.y_prev = self.get_connection_outputs(initialize = True).copy()
+        self.set_last_y(self.y_prev)
+        self.y_discrete_prev = self.get_connection_outputs_discrete(initialize = True).copy()
+
         #Store the inputs
-        self.set_last_us(self.L.dot(self.get_connection_outputs()))
+        self.set_last_us(self.L.dot(self.y_prev))
 
         #Copy FMU address (used when evaluating in parallel)
         self.copy_fmu_addresses()

tests/test_fmi_master.py

@@ -843,3 +843,36 @@ def compute_global_D(self):
               "Actual values may no longer be sensible."
         with pytest.warns(UserWarning, match = re.escape(msg)):
             master.simulate(t_start, t_final, options = opts)
+
+    def test_with_manual_initialization(self):
+        fmu1 = FMUModelCS2(os.path.join(FMI2_REF_FMU_PATH, "Feedthrough.fmu"))
+        fmu2 = FMUModelCS2(os.path.join(FMI2_REF_FMU_PATH, "Feedthrough.fmu"))
+        fmu3 = FMUModelCS2(os.path.join(FMI2_REF_FMU_PATH, "Feedthrough.fmu"))
+
+        models = [fmu1, fmu2, fmu3]
+        connections = [
+            (fmu1, "Float64_continuous_output", fmu2, "Float64_continuous_input"),
+            (fmu2, "Float64_continuous_output", fmu3, "Float64_continuous_input"),
+
+            (fmu1, "Float64_discrete_output", fmu2, "Float64_discrete_input"),
+            (fmu2, "Float64_discrete_output", fmu3, "Float64_discrete_input"),
+        ]
+        master = Master(models, connections)
+        opts = master.simulate_options()
+        opts["step_size"] = 0.1
+        opts["step_size_downsampling_factor"] = {fmu1: 5, fmu2: 2, fmu3: 1}
+
+        fmu1.initialize()
+        fmu2.initialize()
+        fmu3.initialize()
+        opts["initialize"] = False
+
+        res = master.simulate(options = opts)
+
+        assert set(res[0]["Float64_continuous_output"].tolist()) == set([0.])
+        assert set(res[1]["Float64_continuous_output"].tolist()) == set([0.])
+        assert set(res[2]["Float64_continuous_output"].tolist()) == set([0.])
+
+        assert set(res[0]["Float64_discrete_output"].tolist()) == set([0.])
+        assert set(res[1]["Float64_discrete_output"].tolist()) == set([0.])
+        assert set(res[2]["Float64_discrete_output"].tolist()) == set([0.])