improved code and added test for next start index

src/common/io.py

@@ -1630,14 +1630,24 @@ def get_variables_data(self,
         for name in names:
             trajectories[name] = self._get_variable_data_as_trajectory(name, time, start_index, stop_index)
 
-        largest_trajectory_length = -1
-        for v, t in trajectories.items():
-            largest_trajectory_length = max(largest_trajectory_length, len(t.x))
+        largest_trajectory_length = self._find_max_trajectory_length(trajectories)
         new_start_index = (start_index + largest_trajectory_length) if trajectories else start_index
 
         self._last_set_of_indices = (start_index, stop_index) # update them before we exit
         return trajectories, new_start_index
 
+    def _find_max_trajectory_length(self, trajectories):
+        """
+            Given a dict of trajectories, find the length of the largest trajectory
+            among the set of continuous variables. We disregard parameters/constants since they are not stored
+            with the same amount of data points as trajectories for continuous variables.
+        """
+        length = 0
+        for var_name, trajectory in trajectories.items():
+            if self.is_variable(var_name): # since we only consider continuous variables
+                length = max(length, len(trajectory.x))
+        return length
+
     def _calculate_events_and_steps(self, name):
         if name in self._data_3:
             return self._data_3[name]
@@ -1712,15 +1722,13 @@ def is_variable(self, name):
             return True
         elif '{}.'.format(DiagnosticsBase.calculated_diagnostics['nbr_state_limits_step']['name']) in name:
             return True
+
         variable_index  = self.get_variable_index(name)
         data_mat = self._dataInfo[0][variable_index]
-        if data_mat<1:
+        if data_mat < 1:
             data_mat = 1
 
-        if data_mat == 1:
-            return False
-        else:
-            return True
+        return data_mat != 1
 
     def is_negated(self, name):
         """

tests/test_io.py

@@ -24,11 +24,30 @@
 from collections import OrderedDict
 
 from pyfmi import testattr
-from pyfmi.fmi import FMUException, FMUModelME2
-from pyfmi.common.io import (ResultHandler, ResultDymolaTextual, ResultDymolaBinary, JIOError, ResultSizeError,
-                             ResultHandlerCSV, ResultCSVTextual, ResultHandlerBinaryFile, ResultHandlerFile)
-from pyfmi.common.io import get_result_handler
-from pyfmi.common.diagnostics import DIAGNOSTICS_PREFIX, setup_diagnostics_variables
+from pyfmi.fmi import (
+    FMUException,
+    FMUModelME2,
+    FMI2_PARAMETER,
+    FMI2_CONSTANT,
+    FMI2_LOCAL
+)
+from pyfmi.common.io import (
+    ResultHandler,
+    ResultDymolaTextual,
+    ResultDymolaBinary,
+    JIOError,
+    ResultSizeError,
+    ResultHandlerCSV,
+    ResultCSVTextual,
+    ResultHandlerBinaryFile,
+    ResultHandlerFile,
+    Trajectory,
+    get_result_handler
+)
+from pyfmi.common.diagnostics import (
+    DIAGNOSTICS_PREFIX,
+    setup_diagnostics_variables
+)
 
 import pyfmi.fmi as fmi
 from pyfmi.tests.test_util import Dummy_FMUModelME1, Dummy_FMUModelME2, Dummy_FMUModelCS2
@@ -1695,6 +1714,80 @@ def test_csv_options_cs2(self):
 
 class TestResultDymolaBinary:
 
+    def test_next_start_index(self):
+        """
+            Test that calculation of the next start index works as expected.
+
+            This test sets up a dummy FMU and dummy trajectories since we need
+            trajectories of uneven lengths.
+
+        """
+        # Begin by setting up minimal required environment in order to perform the test
+        fmu = Dummy_FMUModelME2([], os.path.join(file_path, "files", "FMUs", "XML", "ME2.0", "CoupledClutches.fmu"),
+            _connect_dll=False)
+
+        result_handler = ResultHandlerBinaryFile(fmu)
+
+        opts = fmu.simulate_options()
+        opts["result_handling"] = "binary"
+        opts["result_handler"] = result_handler
+
+        fmu.setup_experiment()
+        fmu.initialize()
+        opts["initialize"] = False
+
+        result_handler.set_options(opts) # required in order to call simulation_start()
+        result_handler.initialize_complete()
+        result_handler.simulation_start()
+
+        fmu.set('J4.phi', 1) # arbitrary
+        result_handler.integration_point()
+        rdb = ResultDymolaBinary(fmu.get_last_result_file(), allow_file_updates=True)
+
+        # Actual test starts below
+        vars_to_test = [
+            'J1.J',             # this is a parameter
+            'clutch1.Backward'  # this is a constant
+        ]
+
+        # if this is not True, then the rest of test does not hold
+        assert vars_to_test[0] in result_handler.model.get_model_variables(causality = FMI2_PARAMETER).keys()
+        assert vars_to_test[1] in result_handler.model.get_model_variables(variability = FMI2_CONSTANT).keys()
+        assert 'J4.phi' in result_handler.model.states.keys()
+
+
+        for v in vars_to_test:
+            trajectories1 = {
+                'J4.phi': Trajectory(np.array([]), np.array([])),
+                v: Trajectory(np.array([0]), np.array([1]))
+            }
+
+            trajectories2 = {
+                'J4.phi': Trajectory(np.array([0]), np.array([1])),
+                v: Trajectory(np.array([0, 1]), np.array([1, 1]))
+            }
+
+            trajectories3 = {
+                'J4.phi': Trajectory(np.array([0]), np.array([1])),
+                v: Trajectory(np.array([0]), np.array([1]))
+            }
+
+            trajectories4 = {
+                'J4.phi': Trajectory(np.array([0, 1]), np.array([1, 1])),
+                v: Trajectory(np.array([0]), np.array([1]))
+            }
+
+            trajectories5 = {
+                'J4.phi': Trajectory(np.array([0, 1, 2]), np.array([1, 1, 1])),
+                v: Trajectory(np.array([0]), np.array([1]))
+            }
+
+            assert rdb._find_max_trajectory_length(trajectories1) == 0
+            assert rdb._find_max_trajectory_length(trajectories2) == 1
+            assert rdb._find_max_trajectory_length(trajectories3) == 1
+            assert rdb._find_max_trajectory_length(trajectories4) == 2
+            assert rdb._find_max_trajectory_length(trajectories5) == 3
+
     def _test_get_variables_data(self, dynamic_diagnostics: bool, nbr_of_calls: int, diag_data_ratio: int,
                                  vars_to_test: list, stop_index_function: callable, result_file_name: str) -> dict:
         """