MATLAB: The number of workers in PARPOOL is limited to 6 on Linux Cluster

linuxMATLABParallel Computing Toolboxparallel processingparpool

I'm currently working through some stereoscopic video processing on a Linux cluster with 11 physical processors and 126 GiB RAM on 2019A. Each physical process has 8 cores (Opteron 6300 series). For some reason, if I try to create a PARPOOL larger than 6 workers, it fails on the verification step. I'm currently running an analysis, but I will post the specific error message once it's complete. I was originally restricted to fewer than 3 workers, but I increased the size of my Java heap memory to 8GB (using java.opts in the /bin/glnxa64/ directory). Memory usage at 6 workers does not come near system limits. How can I open this up to take advantage of the other physical processors on this machine, increase the java heap memory again?

Best Answer

It will be very useful to see the error message.
It's also not clear what scheduler you are using -- is this a local scheduler, MJS, etc? I'm also assuming that when you say "11 physical processors" you mean 11 nodes in the cluster with 126 GiB each?
My initial hunch is that you are hitting some limit set in the user environment -- something like file handles, RAM, vmem size, etc. In addition to the actual error message it might be useful to see the output of the shell command "ulimit -a" or "limit", depending on what your system uses.
In my experience it's usually been that the "descriptors" is set too low, and it needs to be increased.
You could also be running out of communications ports or hitting a communications error if you have firewalls set up (and are using Parallel Server)
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