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[Bug libfortran/51119] MATMUL slow for large matrices
- From: "jvdelisle at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Wed, 25 Nov 2015 00:48:17 +0000
- Subject: [Bug libfortran/51119] MATMUL slow for large matrices
- Auto-submitted: auto-generated
- References: <bug-51119-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51119
--- Comment #30 from Jerry DeLisle <jvdelisle at gcc dot gnu.org> ---
(In reply to Joost VandeVondele from comment #29)
> These slides show how to reach 90% of peak:
> http://wiki.cs.utexas.edu/rvdg/HowToOptimizeGemm/
> the code actually is not too ugly, and I think there is no need for the
> explicit vector intrinsics with gcc.
The 90% of peak is achieved using SSE registers. I went ahead and built the
example and on my laptop (the slow machine) I get about 4.8 gflops with a
single core. So we could use this example and back-off from the SSE
optimizations to get an internal MATMUL that is not architecture dependent and
perhaps leave the rest to external optimized BLAS.