2016b and later Disk Activity

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Tom
Tom on 9 Feb 2018
Answered: Rahul Kumar on 29 Aug 2018
Hi,
I have a parallel simulation set up using this guide: https://uk.mathworks.com/help/simulink/ug/running-parallel-simulations.html
It's a pretty intense workload, taking around 18 hours on a 40 core, 128GB RAM workstation and it worked fine on R2016a and earlier, but I have recently updated to 2017b and the same script is suddenly using the HDD a lot. This is resulting in the following problems;
1) It's filling my temporary directory with files which eventually causes the script to crash. The script works using a temporary directory for each thread so I expect some disk activity, but R2016b and later seem to be generating a huge amount more data in these directories.
2) I now have to manually delete the temporary files, previously I could using Windows built-in Disk Clean-Up utility to clear the temporary files if the script crashed during a parfor, but this no longer seems to work.
3) Most importantly, I'm running 100,000+ simulations which previously took around 18 hours. With 2016b and later, I'm lucky to get 5% of the simulations done in this time. I think I'm running into the SSD's maximum write speed with 40 threads and the sudden increase in drive activity.
So far, I've found out: - Speed issues are pretty similar to running out of RAM, but I have checked this and I am well under my 128GB. - I have tried all MATLAB versions between R2015a and R2017b. R2016a and earlier run fine, but R2016b and later all have the same issue. - The simulation speed issue behaves like high disk I/O (like running out of RAM). I've confirmed this by watching task manager and seeing high disk activity when running on R2016b and later. - I have identical problems running the script on other PC's, including a quad-core with 16GB RAM. - I have tried parsim on R2017b (https://uk.mathworks.com/help/simulink/slref/parsim.html), but still having similar problems.
I was wondering if anyone was aware of any changes which came into effect with R2016b that might be causing this, and how I could go about fixing the issue?
Regards, Tom
  3 Comments
Striker121
Striker121 on 23 Aug 2018
Having a similar issue using parsim when doing a parameter sweep. The initial simulations run in quick succession but after about 50 simulations, they each take increasingly longer. Is there any way to use a function similar to "Simulink.sdi.clear" with parsim? Unlike parfor, I cannot find a way to run this command during a parameter sweep.

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Answers (1)

Rahul Kumar
Rahul Kumar on 29 Aug 2018

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