How to manage multiple matlab processes running at the same time from python

Question

Christopher Wunder 2021-12-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1602225-how-to-manage-multiple-matlab-processes-running-at-the-same-time-from-python

回答： Swastik 2024-5-22

Hello,

Short Overview

I have a python program, where you can start a matlab script from.

This script collects parameters e.g. initializes them by accessing a database and starts a simulink simulation.

After the simulation is done something is plotted by another matlab function.

For some reason the plot functions hangs when I do simulation + potting in one matlab call.

I couldn't figure out why.

It works fine, when I call them seperately e.g. quit the engine from python, start a new engine and call the plot function. That raises the need to know when my simulation is done, so I can then call the matlab plot function.

Files

I added a text file where you can see my Simulation class in python. It initializes paths for matlab and python modules.

When a simulation is executed by the method execute_simulation in the ThermalSimulation class (see text file), then the matlab process detaches. I can't run the plotting function because the data is not yet generated.

I added the script where parameteres are initialized for the simulink script: "run_script.m"

And the plotting function for the plotting afterwards: "Temperature_Plot_Simulation.m"

Question

The question now is how can I obtain information about when a matlab function is finishe?

In "run_script.m" both, "save_parameters.m" and "Temperature_Plot_Simulation.m" are called, but as I said they DO NOT work, if and only if I call them from my python class from the matlab engine. But they DO from matlab.

I can get the matlab engine process id, e.g. with feature('get_pid') but this pid is from the engine. And I need to know when the simulink simulation is actually finished. Is there a way to get this information? Because only then I can quit the engine and start a new one.

I appreciate any help.

If you happen to know why the plotting won't work in the first place I am happy to know ( the function hangs, when "hold on; grid on; grid minor;" is executed successfully, and then no more ), but I didn't want to ask about both subjects in this question.

Unfortunately you can't run the code really. For the ThermalSimulation you lack the data object, and the simulink model of course.

if any more information is needed, let me know about it.

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Answer 1

Swastik 2024-5-22

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1602225-how-to-manage-multiple-matlab-processes-running-at-the-same-time-from-python#answer_1461511

Hi @Christopher Wunder,

It sounds like you are encountering challenges with plotting simulation results from Simulink and have identified a workaround that involves restarting the Python engine between the simulation and the MATLAB plotting script. To address the issue of the Python process detaching after running the simulation script, I have a couple of suggestions that could streamline your workflow.

Ensuring smooth communication between the simulation completion in Simulink and subsequent MATLAB processes for plotting is your main concern. To facilitate this communication, consider utilizing a shared file as a signalling mechanism. This approach involves writing to a text file at the end of your simulation to signal completion, which can then be checked by other MATLAB processes.

At the end of your Simulink simulation, use the “writelines” function to write a specific line or flag to a text file indicating that the simulation has finished. More details on this can be found here:

https://www.mathworks.com/help/matlab/ref/writelines.html

In your MATLAB script responsible for plotting, use the “fileread” function to check this file for the completion flag before proceeding with plotting. Further information on this function is available here:

https://www.mathworks.com/help/matlab/ref/fileread.html

Instead of using the “sim” function, which halts the MATLAB script until the simulation is complete, you can use “set_param” with your loaded system to start the simulation in a non-blocking manner:

set_param(gcs, SimulinkCommand=”start”)

To check the status of the simulation, utilize:

get_param(gcs, “SimulationStatus”)

This method allows your MATLAB script to continue executing while the simulation runs. You can learn more about managing simulations programmatically here:

https://www.mathworks.com/help/simulink/ug/using-the-sim-command.html#mw_d6991446-2eaf-4729-9d9a-730e2721a2c3

Hope this helps.