Yeah, I think that's where most of the performance gains came from. I
also added a re-write rule for unsafeGet dot (since it doesn't matter
if the arguments are conjugated or not if the vectors are real) that
shaved off about a tenth of a second.
Patrick
On Jul 24, 2008, at 4:26 PM, Don Stewart wrote:
patperry:
Last month Anatoly Yakovenko published some disturbing numbers about
the Haskell BLAS bindings I wrote being significantly slower than
using plain C. I wanted to let everyone know that I've closed the
performance gap, and now for doing ten million dot products, the
overhead for using Haskell instead of C is about 0.6 seconds on my
machine, regardless of the size of the vectors. The next version
will
incorporate the changes. If you can't wait for a formal release, the
darcs repository is at http://www-stat.stanford.edu/~patperry/code/blas/
Anyone interested in more details can check out my blog:
http://quantile95.com/2008/07/24/addressing-haskell-blas-performance-issues/
Thanks everyone for the input on this (especially Anatoly). If any
else finds any performance discrepancies, please let me know and I
will do whatever I can to fix them.
Great work, Patrick!
So if I read correctly, the main change was to flatten the
representation (and thus in loops the vector's structure will be
unpacked and kept in registers, which isn't possible for sum types).
-- Don
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