Issue with Rapid Accelerator Mode in parsim After Upgrading to R2024b

I am encountering issues with the workers in parsim when using the Rapid Accelerator mode.

After upgrading from R2024a to R2024b one week ago, I noticed that running parsim simulations no longer works as expected. I aim to run 6 simulations on a system with 6 physical (P) cores, allowing Matlab to compute all simulations simultaneously. However, only one worker completes the simulation, while the remaining five remain stuck in the "Running" state.

I tested this behavior with 6 identical models, but the issue persisted. Uninstalling and reinstalling Matlab did not do the trick.

Another observation is related to CPU behavior. When the parsim simulation starts, my laptop's fan runs intensively, and some CPU cores reach 100% utilization—this is expected and matches the behavior in R2024a. However, as soon as the first worker completes its simulation, the fan slows down, and CPU utilization becomes erratic. The CPU usage fluctuates significantly, jumping between 20% and 90%.

Additionally, if I stop the parsim simulation via the Simulation Manager, Matlab becomes stuck at the "Cleaning up parallel worker" stage for the workers that were stuck during the simulation.

Interestingly, when switching from Rapid Accelerator to Accelerator mode, the parsim simulations work correctly, and some CPU cores consistently run at 100% utilization.

Does anyone have a clue what the cause for this behavior?

[Oliver Jaehrig]

Is this happening for any model?

If yes, can you check if your anti-virus scanner maybe blocks the executables?

[Christian Hanzl]

Hi Oliver,

Thank you very much for your reply.

I’ve investigated further, and the issue occurs with every model run in Rapid Accelerator mode using parsim in MATLAB R2024b, even with minimal examples. However, when the same models are run in R2024a, they work as expected.

I also checked the Windows Security history for any blocked files or events. There are no entries indicating that any files or actions related to MATLAB have been blocked recently. Actually, there is no entry at all of anything being blocked recently.

Let me know if there’s anything else I should check or if additional details are needed.

Best regards,

Christian