Is return False enabled in do_step()?

[MengnanLi91]

I am working on wrapping our solver with fmu to do co-simulation. In my fmu, I would like to return False in do_step(), but it will result in error "[ERROR] FMI function not supported: fmi2GetBooleanStatus". I need this because our solver is running on side and connecting to fmu via localhost. I want to control the start and stop of the commnunication between this two and end fmu if the connection is end.

Is that supported? Or is there any workaround?

Thanks so much!

class MooseSlave(Fmi2Slave):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs, logging_add_standard_categories=False)

        self.control = MooseControl(moose_port=40000)
        self.control.initialize()

        self.in_val = 0
        self.out_val = 0

        self.register_variable(Real("in_val", causality=Fmi2Causality.input, variability=Fmi2Variability.continuous, start=0.0))
        self.register_variable(Real("out_val", causality=Fmi2Causality.output, variability=Fmi2Variability.continuous))


        self.default_experiment = DefaultExperiment(
        start_time=0.0,    # simulation begins at t=0 s
        stop_time=3.0,    # simulation ends at t=10 s
        step_size=1     # fixed time‐step of 0.01 s
        )


    def do_step(self, current_time, step_size) -> bool:

        active = self.control.isListening()

        if not active:
              print("The simulation is done, please end early")
              return False

        flag = self.control.getWaitingFlag()

        if flag == 'TIMESTEP_BEGIN' and active:

            self.control.wait(flag)

            t_val = self.control.getPostprocessor('t')

            self.in_val = t_val

            print(f"The time gets from MOOSE is {t_val}")

            self.out_val = self.in_val*2

            self.control.setContinue()

        return True

[markaren]

When False is returned fmi2Discard status is returned to the caller.

The issue is really that I suppose the caller then wonder what is wrong, and calls a second FMI function fmi2GetBooleanStatus which is left unimplemented in PythonFMU.

It is not clear to me what fmi2GetBooleanStatus is supposed to do in this case without looking more into it. Could the solver avoid calling this function uppon hitting a discard value?

[MengnanLi91]

fmi2GetBooleanStatus appears in the error message every time when I return False in do_step(). The complete error message is below. I've attached the code to reproduce the error. The mechanism I am looking for is having a early_exit API I can call, so I have more control to end fmu simulation before its end time, e.g. in do_step() function.
'''
[ERROR] FMI function not supported: fmi2GetBooleanStatus
Traceback (most recent call last):
File "moose-fmi/lib/python3.11/site-packages/fmpy/simulation.py", line 1269, in simulateCS
fmu.doStep(currentCommunicationPoint=time, communicationStepSize=step_size)
File "moose-fmi/lib/python3.11/site-packages/fmpy/fmi2.py", line 580, in doStep
self.fmi2DoStep(self.component, currentCommunicationPoint, communicationStepSize, noSetFMUStatePriorToCurrentPoint)
File "moose-fmi/lib/python3.11/site-packages/fmpy/fmi2.py", line 215, in w
raise FMICallException(function=fname, status=res)
fmpy.fmi1.FMICallException: fmi2DoStep failed with status 2 (discard).

During handling of the above exception, another exception occurred:

Traceback (most recent call last):

File "moose-fmi/test/tests/controls/moose_fmu/test_fmu.py", line 24, in
result = simulate_fmu(
^^^^^^^^^^^^^
File "moose-fmi/lib/python3.11/site-packages/fmpy/simulation.py", line 757, in simulate_fmu
result = simulateCS(model_description, fmu, start_time, stop_time, relative_tolerance, start_values, apply_default_start_values, input, output, output_interval, timeout, step_finished, set_input_derivatives, use_event_mode, early_return_allowed, validate, initialize, terminate, set_stop_time)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "moose-fmi/lib/python3.11/site-packages/fmpy/simulation.py", line 1277, in simulateCS
terminate_simulation = fmu.getBooleanStatus(fmi2Terminated)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "moose-fmi/lib/python3.11/site-packages/fmpy/fmi2.py", line 604, in getBooleanStatus
self.fmi2GetBooleanStatus(self.component, kind, byref(value))
File "moose-fmi/lib/python3.11/site-packages/fmpy/fmi2.py", line 215, in w
raise FMICallException(function=fname, status=res)
fmpy.fmi1.FMICallException: fmi2GetBooleanStatus failed with status 3 (error).
'''

Python code to reproduce this error
fmu-test.zip

[markaren]

#244 should make FMPy happy.

[markaren]

To see if this resolves the issue without waiting for a new release.

1. Build native sources (e.g. by calling build_xxx.sh in python-export folder)
2. pip install . in root dir

[MengnanLi91]

Thanks so much! I'll give it a try and let you know.

[MengnanLi91]

I tested it and ran into a platom error as below. The current version of pythonfmu is Version: 0.6.8. I believe it is the latest one.

(moose-fmi) bash-4.4$ python test_fmu.py 
Traceback (most recent call last):
  File "moose-fmi/test/tests/controls/moose_fmu/test_fmu.py", line 21, in <module>
    result = simulate_fmu(
             ^^^^^^^^^^^^^
  File "moose-fmi/lib/python3.11/site-packages/fmpy/simulation.py", line 663, in simulate_fmu
    raise Exception(f"The FMU cannot be simulated on the current platform ({platform}).")
Exception: The FMU cannot be simulated on the current platform (linux64).

[markaren]

Then the native library was not built correctly prior to local pip install. A resources folder should appear with the shared library (.so) in it alongside the python-export folder. Also, open the FMU to check the binary folders content.

[markaren]

You can actually just download the .so from https://github.com/NTNU-IHB/PythonFMU/actions/runs/15910556996 and drop it into the FMU.

[MengnanLi91]

It works perfectly now! I need to rebuild the package because I don't use Ubuntu(I have Rocky Linux), but after that do_step() return False exit elegantly. Thanks so much for the help and quick fix!