Memory increases on GPU while performing modification inplace
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When I allocate squeeze a 3D array to output a 2D array, my memory is increasing while I think I performing the modification inplace. That way I would expect that since the number of elements in the array does not incease, the memory used on the GPU does not increase.
However, I see something different in the task manager. What is going on?
- MATLAB Version: 220.127.116.118580 (R2020a) Update 6
- Operating System: Microsoft Windows 10 Enterprise Version 10.0 (Build 18363)
- NVidia GeForce RTX 3090
data = zeros(5632000, 128, 2, 'int16');
whos RF % int16 2.75 GB
size(RF); % 5632000x128x2
% GPU memory at beginning 1.2 GB
RF = gpuArray(RF); % 3.9 GB
RF = squeezingSuperFrames(RF); % 6.6 GB
function RF = squeezingSuperFrames(RF)
% concatenate pages of 3D array to create tall RF array
RF = reshape(permute(RF, [1 3 2]), , size(RF, 2), 1);
Joss Knight on 10 Oct 2021
MATLAB cannot perform this operation in place because data is a workspace variable. MATLAB has no way of knowing there won't be an error or user interrupt (Ctrl-C) during execution, so it takes a copy of data to ensure your workspace would not be corrupted.