Is there an alternative to parfor?

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Simon
Simon on 21 Dec 2015
Edited: Mohammad Abouali on 23 Dec 2015
Hello,
I run a simulation with several settings. Thus, it is possible to run more than one simulation at one time.
I get the settings from several loops, but before each simulation I check a MySQL database to find out if I run it before. Example:
for S1 = setting1
for S2 = setting2
parfor S3 = setting3
% if S1, S2, S3 is not available in the DB, run it, otherwise continue
end
end
end
It is possible to open Matlab by own 4 times and run the script instead of the parfor with a normal for. In this case, the script is more stable and if there is an error, just one worker stops and not all. This option is way better for the simulation but in the beginning it is not nice to start all manually.
Is there an option to program it this way, or is there a alternative to parfor? Debuging is with parfor also not easy because I don't get the line of the error.

Accepted Answer

Mohammad Abouali
Mohammad Abouali on 22 Dec 2015
Edited: Mohammad Abouali on 23 Dec 2015
Couple of notes here:
NOTE 1 instead of only parallelizing the inner for-loop you can parallelize all of them as follow:
nSetting1=numel(setting1);
nSetting2=numel(setting2);
nSetting3=numel(setting3);
parfor idx=1:(nSetting1*nSetting2*nSetting3)
[idx3,idx2,idx1]=ind2sub([nSetting3,nSetting2,nSetting1],idx);
S1=setting1(idx1);
S2=setting2(idx2);
S3=setting3(idx3);
% if S1, S2, S3 is not available in the DB, run it, otherwise continue
end
The above code parallelize all the loops for you.
NOTE 2 The above code has the same issue as before, meaning if one worker fails all of them stop You can use try/catch block to overcome this as follow:
nSetting1=numel(setting1);
nSetting2=numel(setting2);
nSetting3=numel(setting3);
parfor idx=1:(nSetting1*nSetting2*nSetting3)
[idx3,idx2,idx1]=ind2sub([nSetting3,nSetting2,nSetting1],idx);
S1=setting1(idx1);
S2=setting2(idx2);
S3=setting3(idx3);
try
% if S1, S2, S3 is not available in the DB, run it, otherwise continue
catch
warning('Some error happened. skipping %d,%d,%d',idx1,idx2,idx3);
end
end
The above code generates a warning whenever an error occurs; but it won't stop from working and it continues. Of course you can change the catch block appropriately to do whatever you want it to do.
  2 Comments
Mohammad Abouali
Mohammad Abouali on 23 Dec 2015
Yes. Copy/Paste effect :D Thank you for pointing this out

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