Does copying from gpu to host generally take longer than copying from host to gpu?

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I am using the parallel computing toolbox, and it seems like copying data to a gpu using gpuArray() generally takes much longer than copying data back to the host using gather(). For example, if I try:
A = rand(500,500, 50);
Then the gather() takes about 0.055 seconds while the gpuArray() takes only 0.018 seconds. Is this behavior expected? Am I using the wrong method to time this?

Accepted Answer

Jill Reese
Jill Reese on 16 May 2013
I think you have arrived at the same conclusion as this blog post on GPU performance. It provides a lot of detail on how to properly benchmark GPU operations in MATLAB.
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Adam on 16 May 2013
Thanks for the tip! That blog is very helpful. Does anyone have any idea why the gpu to host copy should be so much slower?

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