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how many workers can I use in parallelization?

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Hello, I am trying to use parallelization and I have one quick question.
I saw another post saying that 'I saw from another post saying that 'All releases newer than R2013b can utilize up to 512 workers (CPU cores) on a local machine through the Parallel Computing Toolbox'
However, I am not sure how many workers I can use with my computer.
I have 32 cores(64 logical cores) and 128 GB of memory.
Does this mean I can use 32 number of workers? or can I use 64 number of workers since I have 64 logical cores?
Or is 'number of workers' something independent from the number of cores?
In the Parallel preferences, I think I can write any number I want as a number of workers so I am bit confused....
Thanks in advance.
Edit. I put 36 as a number of workers in 'Parallel preferences' but when I run the code, it says the number of workers are 32. So I guess Matlab automatically choose the maximum number of workers....?

Accepted Answer

Kojiro Saito
Kojiro Saito on 24 Nov 2021
You need to change the NumWokers property from Cluster Profile.
From "Parallel" -> "Create and Manage Clusters",
change the NumWorkers value to 64 because by default, it is the number of physical CPU cores.
Or, you can change from command line.
First, create a cluster object by parcluster, then change the NumWorkers to 64.
c = parcluster;
c.NumWorkers = 64;
% Do parpool or parfor etc.
  1 Comment
Fabio on 3 May 2024
Thanks for the clear explanation. I hjave a follow up question. Lets say that when I launch my Matlab code 10/32 cores are already used by the program A. Matlab will distribute the calculations on the remaining 22 cores. After 1h the program A is closed. Will Matlab increase the number of cores to 32 to complete the calculation ?
Thanks in advance for your reply.

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