Use parfor and getting "Index exceeds matrix dimensions" error

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NOOR AL-SHAKARJI 2017-2-25

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https://ww2.mathworks.cn/matlabcentral/answers/326845-use-parfor-and-getting-index-exceeds-matrix-dimensions-error

评论： NOOR AL-SHAKARJI 2017-2-26

采纳的回答： Walter Roberson

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Pleas need help , I use Parfor to run the code in parallel but I got "Index exceeds matrix diamensions"

when I run the code with for it runs normally.

Rootpath=('............');
flist1=dir(fullfile(Rootpath));
parfor i=3: size (flist1,1)
       inputpath=strcat(Rootpath,'/',flist1(i).name,'/');
   outpath=strcat('./Output/',flist1(i).name,'/');
   if ~isdir(outpath)
      mkdir(outpath);
   end
      Read_main(inputpath,outpath)
end

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Walter Roberson 2017-2-25

Which line is the error report on?

I recommend by the way that you use fullfile to create the path names

NOOR AL-SHAKARJI 2017-2-26

on parfor line

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Answer 1

Walter Roberson 2017-2-26

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https://ww2.mathworks.cn/matlabcentral/answers/326845-use-parfor-and-getting-index-exceeds-matrix-dimensions-error#answer_256308

You could end up with mysterious path problems in the case that your Rootpath was a global variable. Global variables are not copied to parfor workers.

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Walter Roberson 2017-2-26

If it is a global variable, copy it to a local variable and use that in the code.

Alternately, you can use parfevalOnAll() before running the parfor, running a small bit of code that creates Rootpath as a global variable and initializing it with the appropriate value.

Or since you do not appear to write to the variable in the code, you could use parallel.pool.constant()

But really, for a simple variable such as this, best would just be to avoid using a global variable.

NOOR AL-SHAKARJI 2017-2-26