Add a "sgemm direct" mode for small matrixes #1914
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martin-frbg
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Dec 12, 2018
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yup __restrict solves that, but it looks like AppVeyor timed out or something |
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OpenBLAS has a fancy algorithm for copying the input data while laying it out in a more CPU friendly memory layout. This is great for large matrixes; the cost of the copy is easily ammortized by the gains from the better memory layout. But for small matrixes (on CPUs that can do efficient unaligned loads) this copy can be a net loss. This patch adds (for SKYLAKEX initially) a "sgemm direct" mode, that bypasses the whole copy machinary for ALPHA=1/BETA=0/... standard arguments, for small matrixes only. What is small? For the non-threaded case this has been measured to be in the M*N*K = 28 * 512 * 512 range, while in the threaded case it's less, around M*N*K = 1 * 512 * 512
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(changed whitespace in the commit message to trigger CI to rerun) |
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hm. now appveyor passes but travis did not, so reverse of before. |
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I can restart travis jobs that had a spurious failure, but apparently I cannot do the same with appveyor. |
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OpenBLAS has a fancy algorithm for copying the input data while laying
it out in a more CPU friendly memory layout.
This is great for large matrixes; the cost of the copy is easily
ammortized by the gains from the better memory layout.
But for small matrixes (on CPUs that can do efficient unaligned loads) this
copy can be a net loss.
This patch adds (for SKYLAKEX initially) a "sgemm direct" mode, that bypasses
the whole copy machinary for ALPHA=1/BETA=0/... standard arguments,
for small matrixes only.
What is small? For the non-threaded case this has been measured to be
in the MNK = 28 * 512 * 512 range, while in the threaded case it's
less, around MNK = 1 * 512 * 512
single threaded performance results: