Multiple Parallel Jobs on Server
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Hi,
Let's say I have a script "main.m" which uses the parallel computing toolbox for parallelization. I have a server (Mac) with 20+ cores of cpus, and would like to run multiple "main.m" jobs at the same time for parameter searching. Each "main.m" job only needs 4 cpus. I opened multiple instances of Matlab and ran one job in each instance. However, I found that the speed of each job slows done significantly (compared to just run one single job). I guess it might because some cores are used by more than one job. Suppose 4*number of jobs < 20, what would be a suggested way to achieve the goal? Is there a way to ensure that each job will use different cores?
As a remark, "main.m" is a script and is not a function.
Thanks!
2 Comments
Benjamin Thompson
on 10 Feb 2022
I don't think you can assign jobs to cores like that. Have you tried reducing the size of your parallel pool to maybe 5 instead of 20?
Answers (1)
Edric Ellis
on 11 Feb 2022
You say that "main.m" script uses 4 cores to do parallel computing. I presume this means that it contains a parfor loop. One way you could launch multiple different copies of "main.m" is by using the batch command. Each time you call batch, you get back a parallel.Job object which lets you see how the computation is going, and retrieve the results at the end. By using the 'Pool' parameter to the batch command, you can make the job have a parallel pool available for running the parfor loops. You might do something like this:
for idx = 1:3
param = idx; % param is a variable read by your script "main.m"
job(idx) = batch('main', 'Pool', 4); % Launches "main.m" with a parallel pool of 4 workers
end
% Now that all jobs are launched, we can wait for them to complete and
% collect the result
for idx = 1:3
wait(job(idx));
results{idx} = load(job(idx)); % This will retrieve variables created by "main.m"
end
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