GMP+MPFR to GPU?
tg at gmplib.org
Tue Dec 7 23:36:08 CET 2010
Paul.Zimmermann at loria.fr writes:
concerning the recent thread about GMP+MPFR on GPU, I recommend looking at the
slides of a talk given by Marcelo Kaihara (EPFL) at our seminar:
Slide 30 gives a comparison between GMP and current GPUs, and shows that GMP is
still very competitive.
Alas, the comparison presents strangely low GMP scores. When I time it
now, I get 4900 ops/s while the slides say the very exact number 2738.9.
(I scale my number down from a faster system.) Can OpenSSL possibly add
that much overhead? I very much doubt it. I suspect the guy is using a
quite obsolete GMP release, or a misconfigured GMP.
To make a fair comparison this needs to be done:
1. Use high-end hardware in both cases (i.e., a 3.5 GHz AMD processor)
2. Compare both routines in a raw way, not your own routines in a raw
way and GMP wrapped inside a slow library
3. Use the latest version of both packages
Even with the presented numbers, I am not so sure about the conclusions.
I'd say GPUs are still lame for most bignum calculations, even if
ever-so-advanced lazy carry schemes are implemented.
(I did some research in the area for Cray about 1 years ago, and
explored many of the tricks suggested in the slides. Some if it is in
GMP's mpn/cray/ieee directory since then. The mul_basecase code therein
avoids almost all inter-dependencies.)
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