Your code is not standalone, so I couldn't try it. But the main point is that you need to vectorise your code. This will speed things up on the CPU, and will speed them up even more on the GPU. You will also end up with simpler code. To keep the GPU busy, you need to give it big chunks of work to do all at once. Your code was operating on arrays one element at a time - that sometimes works out OK on the CPU, but is always terrible on the GPU.
There's some general guidance on vectorisation in the documentation here: https://www.mathworks.com/help/matlab/matlab_prog/vectorization.html .
To take a tiny example from your code:
Difference=zeros(videoObject.Height,videoObject.Width,videoObject.NumFrames,'gpuArray');
for ii=1:videoObject.Height
for jj=1:videoObject.Width
for kk=1:videoObject.NumFrames
Difference(ii,jj,kk)=abs(double(blackAndWhiteVideo(ii,jj,kk))-double(BackGround(ii,jj)));
end
end
end
This is a perfect example where vectorisation can help. In fact, in recent releases of MATLAB, you can use MATLAB's implicit dimension expansion to make this whole block extremely concise:
% Step 1: transfer the two input arrays to the GPU, and
% convert them to 'double'
bwGpu = double(gpuArray(blackAndWhiteVideo));
bgGpu = double(gpuArray(BackGround));
% Step 2: compute the difference, and then call 'abs' (on the GPU).
Difference = abs(bwGpu - bgGpu);
The crucial point here is that the subtraction implicitly expands your "background" array in the third dimension to match the size of blackAndWhiteVideo.
