Arrayfun GPU in "Game of Life" works slower than CPU

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Uladzislau
Uladzislau on 18 Mar 2020
Edited: Joss Knight on 28 Mar 2020
Hello! I've run the demo "paralleldemo_gpu_stencil" and have such a result:
CPU: 2.815ms per generation.
Simple GPU: 2.650ms per generation (1.1x faster).
Arrayfun GPU: 13.253ms per generation (0.2x faster).
I've used ThinkPad P50 with Quadro M1000M and Matlab R2019b with appropriate drivers. Why Arrayfun works such slow ??
Uladzislau.

Accepted Answer

Joss Knight
Joss Knight on 28 Mar 2020
Edited: Joss Knight on 28 Mar 2020
Check out this Answer. The arrayfun version is rather dependent on good memory performance since the kernel is accessing global GPU memory in a non-coalesced way (multiple threads accessing overlapping regions of memory that aren't contiguous). For your chip, the version that runs multiple kernels on multiple shifted copies of the grid is actually more efficient, despite the kernel launch overhead and the extra memory allocation needed.

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