Support AVX

2011-07-04, 11:46

Support the next version of Prime95 AVX? If yes, is already known when this version is available?

Prime95 · 2011-07-04, 13:24

Yes to AVX. No as to a known date.

At present, FFT sizes 32, 128, 512, and 2048 are coded and mostly working.

henryzz · 2011-07-04, 16:57

Quote:

Originally Posted by Prime95

Yes to AVX. No as to a known date.

At present, FFT sizes 32, 128, 512, and 2048 are coded and mostly working.

Any hints as to speed increase on these FFTs?

Prime95 · 2011-07-04, 18:02

Just got numbers for the 2K FFT:

SSE2: 100 iters in 1.110 ms
AVX: 100 iters in 0.682 ms

I'm not sure if these numbers will extrapolate to large FFTs. These small FFTs operate completely in the L1 cache.

henryzz · 2011-07-04, 19:11

Quote:

Originally Posted by Prime95

Just got numbers for the 2K FFT:

SSE2: 100 iters in 1.110 ms
AVX: 100 iters in 0.682 ms

I'm not sure if these numbers will extrapolate to large FFTs. These small FFTs operate completely in the L1 cache.

Nice. I use the smaller FFTs most of the time in LLR anyway so I am not too worried.

ixfd64 · 2011-07-05, 17:12

Quote:

Originally Posted by Prime95

Just got numbers for the 2K FFT:

SSE2: 100 iters in 1.110 ms
AVX: 100 iters in 0.682 ms

These timings seem consistent with the fact that AVX is not twice as fast as SSE2 despite the increase to 256 bits. Hopefully AVX2 and the new Tri-Gate chips will "fix" this.

2011-07-04, 11:46	#1
Unregistered 2·5·653 Posts	Support AVX Support the next version of Prime95 AVX? If yes, is already known when this version is available?

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2011-07-04, 13:24	#2
Prime95 P90 years forever! Aug 2002 Yeehaw, FL 2³×1,021 Posts	Yes to AVX. No as to a known date. At present, FFT sizes 32, 128, 512, and 2048 are coded and mostly working.

2011-07-04, 18:02	#4
Prime95 P90 years forever! Aug 2002 Yeehaw, FL 2³×1,021 Posts	Just got numbers for the 2K FFT: SSE2: 100 iters in 1.110 ms AVX: 100 iters in 0.682 ms I'm not sure if these numbers will extrapolate to large FFTs. These small FFTs operate completely in the L1 cache.