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improve returned data if running a simulation (using the model executable)#398

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improve returned data if running a simulation (using the model executable) #398

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50f9a91
[OMCSession] improve log messages for model simulation using OM execu…
syntron Dec 15, 2025
3c316a9
[ModelicaSystem] improve handling of model simulation
syntron Dec 15, 2025
1efdcc7
[ModelicaSystemDoE] fix exception handling
syntron Dec 16, 2025
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12 changes: 6 additions & 6 deletions OMPython/ModelicaSystem.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -1185,15 +1185,15 @@ def simulate(
cmd_definition = om_cmd.definition()
returncode = self._session.run_model_executable(cmd_run_data=cmd_definition)
# and check returncode *AND* resultfile
if returncode != 0 and self._result_file.is_file():
if returncode != 0:
# check for an empty (=> 0B) result file which indicates a crash of the model executable
# see: https://github.com/OpenModelica/OMPython/issues/261
# https://github.com/OpenModelica/OpenModelica/issues/13829
if self._result_file.size() == 0:
if self._result_file.is_file() and self._result_file.size() == 0:
self._result_file.unlink()
raise ModelicaSystemError("Empty result file - this indicates a crash of the model executable!")

logger.warning(f"Return code = {returncode} but result file exists!")
logger.warning(f"Return code = {returncode} but result file was created!")

self._simulated = True

Expand DownExpand Up@@ -2188,9 +2188,9 @@ def worker(worker_id, task_queue):
try:
returncode = self.get_session().run_model_executable(cmd_run_data=cmd_definition)
logger.info(f"[Worker {worker_id}] Simulation {resultpath.name} "
f"finished with return code: {returncode}")
except ModelicaSystemError as ex:
logger.warning(f"Simulation error for {resultpath.name}: {ex}")
f"finished with return code {returncode}")
except OMCSessionException as ex:
logger.warning(f"Error executing {repr(cmd_definition.get_cmd())}: {ex}")

# Mark the task as done
task_queue.task_done()
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11 changes: 7 additions & 4 deletions OMPython/OMCSession.py
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Expand Up@@ -830,20 +830,23 @@ def run_model_executable(self, cmd_run_data: OMCSessionRunData) -> int:
env=my_env,
cwd=cmd_run_data.cmd_cwd_local,
timeout=self._timeout,
check=True,
check=False,

@bilderbuchibilderbuchiDec 16, 2025•
edited
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Getting an exception on non-zero exit code was good. Exceptions for handling control flow in Python are totally fine, and obvious to the user, and hard to miss, I would keep that. (I did not realize that that's what's happening because I did not dig deep enough in the call hierarchy)

The additional logging is good, so I'd keep that too. 👍

@syntronsyntronDec 16, 2025

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The exception on non-zero exit code has to be handled with care. There are possibilities that a result file is created (and usefull) even if the exit code is != 0. An exception here would prevent any processing of such data.

If I remeber correctly, an example is if the model is terminated via Modelica code.

@bilderbuchibilderbuchiDec 17, 2025

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If I remeber correctly, an example is if the model is terminated via Modelica code.

You mean via terminate()? If yes a nonzero exit code would be strange, because this "successfully terminates the analysis which was carried out".

@adeas31adeas31Feb 9, 2026

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For me, this change is fine. It’s also consistent with how we handle this in OMEdit: we show the user what happened when running the executable, and if there’s any useful output, we use it for post-processing. If an exception is raised, that post-processing will not happen anyway.

Regarding check=True, it does the following:

If check is True and the exit code is non-zero, a CalledProcessError is raised. The CalledProcessError object contains the return code in the returncode attribute, and the output and stderr attributes if those streams were captured.

The new code already covers this behavior: it explicitly checks the returncode and logs it.

)
stdout = cmdres.stdout.strip()
stderr = cmdres.stderr.strip()
returncode = cmdres.returncode

logger.debug("OM output for command %s:\n%s", repr(cmdl), stdout)
if returncode != 0:
logger.warning("OM executable run %s with returncode=%d and stdout:\n%s",
repr(cmdl), returncode, stdout)
else:
logger.debug("OM executable run %s with stdout:\n%s", repr(cmdl), stdout)

if stderr:
raise OMCSessionException(f"Error running model executable {repr(cmdl)}: {stderr}")

except subprocess.TimeoutExpired as ex:
raise OMCSessionException(f"Timeout running model executable {repr(cmdl)}") from ex
except subprocess.CalledProcessError as ex:
raise OMCSessionException(f"Error running model executable {repr(cmdl)}") from ex

return returncode

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