Fix performance degradation of HIP dot#207
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The results did not match between cuda-stream and hip-stream on the same NVIDIA GPU card (NVIDIA A100 40GB PCIe) when large arraysize is specified. cuda-stream uses the number of SMs to decide dot_num_blocks, which looks more sensible than to use arraysize to determine the parameter. It is used as kernel grid size and iteration count for reduction in the host code. Link: UoB-HPC@9954b7d Signed-off-by: Daisuke Matsuda <matsuda-daisuke@fujitsu.com>
Signed-off-by: Daisuke Matsuda <matsuda-daisuke@fujitsu.com>
Signed-off-by: Daisuke Matsuda <matsuda-daisuke@fujitsu.com>
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@thomasgibson - can you comment on this as I think you wrote the current HIP version? |
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The workload of dot calculation is not consistent among the different implementations. The larger the arraysize, the longer it takes for the HIP version to complete.
The HIP version currently uses arraysize to determine 'dot_num_blocks', which is used as kernel grid size and iteration count for reduction in the host code. The CUDA counterpart uses the number of SM (based on GPU specs) to determine 'dot_num_blocks'. The result should be more reliable with the CUDA one because of higher occupancy and more reasonable overhead of reduction on the host.