Parfor loop classification "fix usage of indicated variable" error
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I'm running a parfor loop and I'm trying to output an array with the columns representing each parfor iteration, and the row elements are converted to a non-zero value at specific locations for each column index. The non-zero element row index is different for every iteration.
The problem: Unable to classify the variable 'Binarizing_Rowsum' in the body of the parfor-loop. For more information, see Parallel for Loops in MATLAB, "Solve Variable Classification Issues in parfor-Loops".
I tried to understand how to fix it by readig the documentation and other answers on the forum but I'm lost. I understand it is considered a sliced variable, however, I don't know how to fix the representation of the variable so that it matchs parfor requirements to get the output I want.
P.S. the correspoding for-loop worked perfectly
Here is the code:
jValues=1:2:length(baseFileNames)-1;
Binarizing_Rowsum=zeros(6100,length(jValues));
LEDdurIndx=NaN(1000,length(jValues));
Light=3000;
parfor idx=1:numel(jValues)
j=jValues(idx);
%Read files
fullFileName=fullfile(thisFolder, baseFileNames{j});
C_data_Array(:,:,idx)= imread(fullFileName,2);
C_data_ArrayMean(:,:,idx)=mean(C_data_Array(:,:,idx),2);
C_data_ArrayStd(:,:,idx)=std(C_data_ArrayMean(:,:,idx));
LEDdetectThresh=(mean(C_data_ArrayMean(:,:,idx),1))+C_data_ArrayStd(:,:,idx);
LEDdurIndx=find(C_data_ArrayMean(:,:,idx)>LEDdetectThresh);
LED_duration_=LEDdurIndx([1,end]); %Updated
LEDinit(idx)=LED_duration(1);%Updated
LEDend(idx)=LED_duration(2);%Updated
Binarizing_Rowsum([LEDdurIndx],idx)=Light; %OUTPUT ERROR: cannot be classified
end
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回答(3 个)
Walter Roberson
2022-8-17
BR = Binarizing_Rowsum(:,idx);
BR(LEDdurIdx) = Light;
Binarizing_Rowsum(:, idx) = BR;
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Edric Ellis
2022-8-19
Inside your loop, you are assigning a whole new value to LEDdurIndx. This makes the variable a parfor "temporary", and so any value assigned inside the loop is discarded. I don't see any such problem for Binarizing_Rowsum though...
Bruno Luong
2022-8-19
编辑:Bruno Luong
2022-8-19
LEDdetectThresh=(mean(C_data_ArrayMean(:,:,idx),1))+C_data_ArrayStd(:,:,idx);
LEDdurIndx=find(C_data_ArrayMean(:,:,idx)>LEDdetectThresh)
I suspect the code is buggy, the mean can never be bigger than mean + std
LEDdurIndx is therefore empty.
Bruno Luong
2022-8-22
编辑:Bruno Luong
2022-8-22
Your code is good to be called "spagetti". If all the image have the same size, you must tell parfor what they are:
jValues=1:2:length(baseFileNames)-1;
n = numel(jValues);
Binarizing_Rowsum=zeros(6100,n);
LEDdurIndx=NaN(1000,n);
Light=3000;
j=jValues(1);
%Read first file to figure out the array sizes
fullFileName=fullfile(thisFolder, baseFileNames{j});
I1= imread(fullFileName,2);
[p,q]=size(I1);
C_data_Array = zeros(p,q,n);
C_data_ArrayMean = zeros(p,1,n);
C_data_ArrayStd = zeros(1,q,n);
LEDdetectThresh = zeros(1,q,n);
Binarizing_Rowsum = zeros(p*q,n);
parfor idx=1:n
j=jValues(idx);
%Read files
fullFileName=fullfile(thisFolder, baseFileNames{j});
C_data_Array(:,:,idx)= imread(fullFileName,2);
C_data_ArrayMean(:,:,idx)=mean(C_data_Array(:,:,idx),2);
C_data_ArrayStd(:,:,idx)=std(C_data_ArrayMean(:,:,idx));
LEDdetectThresh=(mean(C_data_ArrayMean(:,:,idx),1))+C_data_ArrayStd(:,:,idx);
LEDdurIndx = find(C_data_ArrayMean(:,:,idx)>LEDdetectThresh);
LED_duration_=LEDdurIndx([1,end]); %Updated
LEDinit(idx)=LED_duration(1);%Updated
LEDend(idx)=LED_duration(2);%Updated
Temp = zeros(p*q,1);
Temp(LEDdurIndx) = Light;
Binarizing_Rowsum(:,idx)=Temp;
end
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