parfor loop variable classification

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Quentin
Quentin on 31 Aug 2014
Edited: Adam on 1 Sep 2014
Hi all,
I have always had trouble getting parlor loops to work for me, and again I'm having a variable classification issue. The code is for a machine vision program that we are using to detect blobs in multiple behavioral chambers in a video. We would basically like to use a parfor loop to find the blobs in each frame more rapidly. We'll track them across frames later. This way it would seem like if we built a small computer cluster, we could speed up the code a lot. Basically this is what we are trying to do with several of our variables (I've shown only one for an example).
recordAValue = NaN(blobsPerChamber, numberOfChambers, numberOfFrames);
parfor g = 1:numberOfFrames
load(frame);
for k = 1:numberOfChambers
findBlobs
for j = 1: blobsPerChamber
recordAValue(j,k,g) = someCalculation;
end
end
end
The error that I would get is that recordAValue cannot be classified. I've looked at the documentation but I still can't make sense of it. The loops all seem independent to me and the matrix recordAValue should be able to be generated one loop at a time.
Any help is appreciated. Thanks in advance.
  2 Comments
Edric Ellis
Edric Ellis on 1 Sep 2014
Hm. The following simplified example works for me:
out = NaN(6, 5, 4);
parfor idx = 1:4
for jdx = 1:5
for kdx = 1:6
out(kdx, jdx, idx) = 7;
end
end
end
What version of MATLAB are you using?
Adam
Adam on 1 Sep 2014
Edited: Adam on 1 Sep 2014
What are 'someCalculation' and 'findBlobs' and where/how are they defined? They may be breaking transparency rules for parfor loops as they could theoretically be anything as it is currently stated.

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