Memory problem when accessing and copying the 3D array elements by subscripts

Question

Preetham Manjunatha 2021-8-2

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https://ww2.mathworks.cn/matlabcentral/answers/890547-memory-problem-when-accessing-and-copying-the-3d-array-elements-by-subscripts

评论： Preetham Manjunatha 2021-8-2

I am trying to access/copy values from an image 3D array to another 3D array using the subcripts (rows and columns). I am trying to avoid the for loop. With for loop this works fine. The size of the rows and columns is 121020 x 1. But I am getting a memory error as below:

Requested 121020x121020x3 (40.9GB) array exceeds maximum array size preference. Creation of arrays greater than this limit may take a
long time and cause MATLAB to become unresponsive.

The code snippet is below

% Find boundary of the cylindrical projection
[row,col] = find(ximg > 0 & ximg <= xdim & yimg > 0 & yimg <= ydim);
out(row,col,:) = image(row,col,:);

Any help to make it without for loop is appreciated!

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Preetham Manjunatha 2021-8-2

Image size is 384 x 512 x 3. So xdim is 512 and ydim is 384.

darova 2021-8-2

what is size of ximg?

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Answer 1

Matt J 2021-8-2

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https://ww2.mathworks.cn/matlabcentral/answers/890547-memory-problem-when-accessing-and-copying-the-3d-array-elements-by-subscripts#answer_759087

编辑：Matt J 2021-8-2

在 MATLAB Online 中打开

The better way would be to avoid using find():

region=(ximg > 0 & ximg <= xdim & yimg > 0 & yimg <= ydim);
imtmp=reshape(image,[],size(image,3));
outtmp=reshape(out,[],size(out,3));
outtmp(region,:)=imtmp(region,:);
out(:)=outtmp(:); clear outtmp imtmp