-----Original Message-----
From: mpir-devel@googlegroups.com [mailto:mpir-devel@googlegroups.com] On
Behalf Of Bill Hart
Sent: Thursday, March 15, 2012 1:09 PM
To: mpir-devel@googlegroups.com
Subject: Re: [mpir-devel]
Now that I am not on my mobile I can access the article and I see that they are
comparing with GMP (though they don't say what version -- and it makes a big
difference). [They also reference GMP as being written by the "GNU Open Source
Community". The GNU people would not be thrilled about that. They don't use the
phrase "Open Source" but "Free Software".]
Anyhow, the GPU only seems to beat the CPUs when the multiplications are small,
basically below the FFT range. Either way, the GPU is giving some speedup,
assuming they compared with a recent GMP. So it is interesting.
>>
It looks to me like it is faster for the CUDA card than for the CPU everywhere
(at least in the places that they tested). Consider "Table 1. CPU single core
vs GPU - multiplication time (in milliseconds)" on article page 372:
Table 1. CPU single core vs GPU - multiplication time (in milliseconds)
Size in K bits Core 2 Q6600 Core i7 870 GTX 295 GTX 295 GTX
480
Old Code New Code New Code
-----------------------------------------------------------------------------------------
255 x 255 2.071 1.368 0.813
n/a n/a
383 x 383 3.266 2.154 n/a
0.451 0.156
510 x 510 4.649 3.032 2.010
n/a n/a
766 x 766 7.263 4.834 n/a
0.957 0.317
1020 x 1020 10.381 6.792 5.418
n/a n/a
1532 x 1532 16.119 10.937 n/a
1.821 0.584
2040 x 2040 23.576 15.738 15.389 3.544
1.122
4080 x 4080 53.653 35.283 43.954 7.968
2.395
8160 x 8160 141.655 80.479 129.358 16.627
4.924
16320 x 16320 297.032 186.751 386.083 27.841
9.666
I interpret this to mean (for instance) that my i7 can multiply two 383 bit
numbers in 2.154 milliseconds but my GTX 480 can do the job in .156 ms. (Ratio:
2.154 /0.156=13.8 times faster )
Further, my i7 CPU can multiply two 16,320 bit numbers in 27.841 ms but the GTX
480 can do it in 9.666 seconds (Ratio: 186.751/9.666=19.32 times faster)
I guess that for one million bit numbers the benefit will be even greater.
I do not know if this table takes into account the copy time or not. It might
be worthwhile to contact the original authors for clarification.
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