Parfor: Unable to perform assignment because the size of the left side is 98-by-50 and the size of the right side is 107-by-50

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Abigail Allen 2020-4-13

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评论： Camila Gil 2021-3-1

Hello,

I have been trying to modify the speech command recognition example (https://uk.mathworks.com/help/audio/examples/Speech-Command-Recognition-Using-Deep-Learning.html) by adding in one of my own words into the data set.

However when I get to the feature extraction for the valdation set, I get the error "Unable to perform assignment because the size of the left side is 98-by-50 and the size of the right side is 107-by-50" on the line:

parfor ii = 1:numPar

I am unsure of why this section is flagging an error when my test set did this without any hiccups. Any help on this would be much appreciated, thank you!

Here is the section of code it occurs in:

%%
% Perform the feature extraction steps described above to the validation
% set.
if ~isempty(ver('parallel'))
    pool = gcp;
    numPar = numpartitions(adsValidation,pool);
else
    numPar = 1;
end
parfor ii = 1:numPar
    subds = partition(adsValidation,numPar,ii);
    XValidation = zeros(numHops,numBands,1,numel(subds.Files));
    for idx = 1:numel(subds.Files)
        x = read(subds);
        xPadded = [zeros(floor((segmentSamples-size(x,1))/2),1);x;zeros(ceil((segmentSamples-size(x,1))/2),1)];
        XValidation(:,:,:,idx) = extract(afe,xPadded);
    end
    XValidationC{ii} = XValidation;
end
XValidation = cat(4,XValidationC{:});
XValidation = XValidation/unNorm;
XValidation = log10(XValidation + epsil);

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Answer 1

Edric Ellis 2020-4-14

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Unfortunately, error reporting from parfor has some limitations, and specifically it cannot indicate the precise line within the loop body where the error is occurring.

Having said that, I cannot see in your loop body any places where you're performing a 2-dimensional assignment operation to generate the error that you're observing... (although my guess would be the assignment into XValidation).

One option in this case is to place the entire body of your parfor loop into a separate function - that way when things do fail, you should get a more precise error location. Something like this:

parfor ii = 1:numPar
    % Unfortunately, it looks like you'll need to pass through quite a number of parameters.
    XValidationC{ii} = loopBodyFcn(adsValidation, numPar, ii, numHops, numBands); % more here
end

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Abigail Allen 2020-4-18

Thanks Edric, using a for loop gave a much better understanding of the error. Turned out to be tha the new data I was adding was sampled at a much higher rate so the files were bigger. This in turn meant that it wasn't the same size as the other samples which was why this error occured! Thanks for the help :)

Camila Gil 2021-3-1