question on using parfor

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Baozai on 22 Nov 2016
Commented: Alexandra Harkai on 24 Nov 2016
Hello, all.
I got a question on using parfor in matlab. When I tried to run the following code, I got an error showing:"Error: The variable Resp in a parfor cannot be classified.". Is this because Resp will be generated simultaneously when jjjj will be executed parallelly? If so, does this mean I can not perform this since different Phi use the same Resp as the first structure name? Will there be any idea on solving this problem? Thank you very much.
The following are the codes:
sizePhiValuep = 7;
sizeMassp = 20;
parfor (jjjj=1:sizePhiValuep,7)
Resp.(sprintf('Phi%d',jjjj)).MaxX2RespBegin_beta= zeros(sizeMassp,1);
Resp.(sprintf('Phi%d',jjjj)).MaxX2RespEnd_beta= zeros(sizeMassp,1);

Accepted Answer

Alexandra Harkai
Alexandra Harkai on 22 Nov 2016
The error message refers to the variable classification when using parfor: classification-of-variables-in-parfor-loops. It doesn't know if you'll operate on segments in each loop or accumulate values regardless of the iteration order.
You could make Resp-something an array (or two arrays, if you need Begin and End) and index into that from the corresponding loop using jjjj.

More Answers (1)

Baozai on 23 Nov 2016
Thank you, Alexandra, When I change the code to the following, it works.
sizePhiValuep = 7;
sizeMassp = 20;
parfor (jjjj=1:sizePhiValuep,7)
Resp(jjjj).Phi.MaxX2RespBegin_beta= zeros(sizeMassp,1);
Resp(jjjj).Phi.MaxX2RespEnd_beta= zeros(sizeMassp,1);
  1 Comment
Alexandra Harkai
Alexandra Harkai on 24 Nov 2016
Dynamic variable name generation for indexing purposes ( sprintf('Phi%d',jjjj) ) should be avoided anyway, so it's always good practice to use 'actual' indexing instead.

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