Warn users when restarting with fix_final=True (OpenMDAO#804)

* added a warning if load case is called while fix_final is set to True

* added test case

* added similar warnings for controls and polynomial controls

* switched warning to issue_warning

Co-authored-by: Kaushik Ponnapalli <kaushik.s.ponnapalli@nasa.gov>

dymos/load_case.py

@@ -2,6 +2,7 @@
 from openmdao.recorders.case import Case
 from .phase.phase import Phase
 from .trajectory import Trajectory
+from openmdao.utils.om_warnings import issue_warning
 
 
 def find_phases(sys):
@@ -149,6 +150,12 @@ def load_case(problem, previous_solution):
             if init_val_path:
                 problem.set_val(init_val_path[0], prev_state_val[0, ...], units=prev_state_units)
 
+            if options['fix_final']:
+                warning_message = f"{phase_name}.states:{state_name} specifies 'fix_final=True'. " \
+                                  f"If the given restart file has a" \
+                                  f" different final value this will overwrite the user-specified value"
+                issue_warning(warning_message)
+
         # Interpolate the timeseries control outputs from the previous solution onto the new grid.
         for control_name, options in phase.control_options.items():
             control_path = [s for s in phase_vars if s.endswith(f'{phase_name}.controls:{control_name}')][0]
@@ -160,6 +167,11 @@ def load_case(problem, previous_solution):
                             phase.interp(xs=prev_time_val, ys=prev_control_val,
                                          nodes='control_input', kind='slinear'),
                             units=prev_control_units)
+            if options['fix_final']:
+                warning_message = f"{phase_name}.controls:{control_name} specifies 'fix_final=True'. " \
+                                  f"If the given restart file has a" \
+                                  f" different final value this will overwrite the user-specified value"
+                issue_warning(warning_message)
 
         # Set the output polynomial control outputs from the previous solution as the value
         for pc_name, options in phase.polynomial_control_options.items():
@@ -169,6 +181,11 @@ def load_case(problem, previous_solution):
             prev_pc_val = prev_vars[prev_pc_path]['val']
             prev_pc_units = prev_vars[prev_pc_path]['units']
             problem.set_val(pc_path, prev_pc_val, units=prev_pc_units)
+            if options['fix_final']:
+                warning_message = f"{phase_name}.polynomial_controls:{pc_name} specifies 'fix_final=True'. " \
+                                  f"If the given restart file has a" \
+                                  f" different final value this will overwrite the user-specified value"
+                issue_warning(warning_message)
 
         # Set the timeseries parameter outputs from the previous solution as the parameter value
         for param_name, options in phase.parameter_options.items():

dymos/test/test_load_case.py

@@ -8,7 +8,8 @@
 om_version = tuple([int(s) for s in openmdao.__version__.split('-')[0].split('.')])
 
 
-def setup_problem(trans=dm.GaussLobatto(num_segments=10), polynomial_control=False):
+def setup_problem(trans=dm.GaussLobatto(num_segments=10), polynomial_control=False,
+                  fix_final_state=True, fix_final_control=False):
     from dymos.examples.brachistochrone.brachistochrone_ode import BrachistochroneODE
 
     p = om.Problem(model=om.Group())
@@ -20,15 +21,16 @@ def setup_problem(trans=dm.GaussLobatto(num_segments=10), polynomial_control=Fal
 
     phase.set_time_options(fix_initial=True, duration_bounds=(.5, 10))
 
-    phase.add_state('x', fix_initial=True, fix_final=True)
-    phase.add_state('y', fix_initial=True, fix_final=True)
+    phase.add_state('x', fix_initial=True, fix_final=fix_final_state)
+    phase.add_state('y', fix_initial=True, fix_final=fix_final_state)
     phase.add_state('v', fix_initial=True)
 
     if not polynomial_control:
         phase.add_control('theta', units='deg',
-                          rate_continuity=False, lower=0.01, upper=179.9)
+                          rate_continuity=False, lower=0.01, upper=179.9, fix_final=fix_final_control)
     else:
-        phase.add_polynomial_control('theta', order=1, units='deg', lower=0.01, upper=179.9)
+        phase.add_polynomial_control('theta', order=1, units='deg', lower=0.01, upper=179.9,
+                                     fix_final=fix_final_control)
 
     phase.add_parameter('g', units='m/s**2', opt=False, val=9.80665)
 
@@ -186,6 +188,77 @@ def test_load_case_radau_to_lgl(self):
                           q.model.phase0.interp(xs=time_val, ys=theta_val, nodes='all'),
                           tolerance=1.0E-2)
 
+    def test_load_case_warn_fix_final_states(self):
+        import openmdao.api as om
+        from openmdao.utils.assert_utils import assert_warnings
+        import dymos as dm
+
+        p = setup_problem(dm.Radau(num_segments=20))
+
+        # Solve for the optimal trajectory
+        dm.run_problem(p)
+
+        # Load the solution
+        case = om.CaseReader('dymos_solution.db').get_case('final')
+
+        # create a problem with a different transcription with a different number of variables
+        q = setup_problem(dm.GaussLobatto(num_segments=50))
+
+        msgs = []
+
+        # Load the values from the previous solution
+        for state_name in ['x', 'y']:
+            msgs.append((UserWarning, f"phase0.states:{state_name} specifies 'fix_final=True'."
+                                      f" If the given restart file has a different final value"
+                                      f" this will overwrite the user-specified value"))
+
+        with assert_warnings(msgs):
+            dm.load_case(q, case)
+
+    def test_load_case_warn_fix_final_control(self):
+        import openmdao.api as om
+        from openmdao.utils.assert_utils import assert_warning
+        import dymos as dm
+        p = setup_problem(dm.Radau(num_segments=10))
+
+        # Solve for the optimal trajectory
+        dm.run_problem(p)
+
+        # Load the solution
+        case = om.CaseReader('dymos_solution.db').get_case('final')
+
+        # create a problem with a different transcription with a different number of variables
+        q = setup_problem(dm.Radau(num_segments=10), fix_final_state=False, fix_final_control=True)
+
+        msg = f"phase0.controls:theta specifies 'fix_final=True'. If the given restart file has a" \
+              f" different final value this will overwrite the user-specified value"
+
+        with assert_warning(UserWarning, msg):
+            dm.load_case(q, case)
+
+    def test_load_case_warn_fix_final_polynomial_control(self):
+        import openmdao.api as om
+        from openmdao.utils.assert_utils import assert_warning
+        import dymos as dm
+        p = setup_problem(dm.Radau(num_segments=10), polynomial_control=True,)
+
+        # Solve for the optimal trajectory
+        dm.run_problem(p)
+
+        # Load the solution
+        case = om.CaseReader('dymos_solution.db').get_case('final')
+
+        # create a problem with a different transcription with a different number of variables
+        q = setup_problem(dm.Radau(num_segments=10), polynomial_control=True,
+                          fix_final_state=False, fix_final_control=True)
+
+        # Load the values from the previous solution
+        msg = f"phase0.polynomial_controls:theta specifies 'fix_final=True'. If the given restart file has a" \
+              f" different final value this will overwrite the user-specified value"
+
+        with assert_warning(UserWarning, msg):
+            dm.load_case(q, case)
+
 
 if __name__ == '__main__':  # pragma: no cover
     unittest.main()