mersenneforum.org > Math Multiple (prp) test at once?
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 2021-05-15, 20:55 #1 R. Gerbicz     "Robert Gerbicz" Oct 2005 Hungary 3×13×41 Posts Multiple (prp) test at once? When you are loading from a precomputed cos/sin table at fft or compute these in-fly then you could reuse these values. Basically hide/halve this computation cost [or just the cost of load] if you'd compute multiple fft test at once. Ofcourse use "close" N values, so close p values [for Mersenne numbers] to have the same FFT size for the problems. Say you'd compute cos(d)*a1[i]+sin(d)*b1[i] cos(d)*a2[i]+sin(d)*b2[i] or for more than 2 tests: cos(d)*a3[i]+sin(d)*b3[i] cos(d)*a4[i]+sin(d)*b4[i] etc. Got the idea?
2021-05-15, 23:47   #2
chalsall
If I May

"Chris Halsall"
Sep 2002

2·5,431 Posts

Quote:
 Originally Posted by R. Gerbicz Got the idea?
Yes. Thank you. Clear.

2021-05-17, 12:17   #3
preda

"Mihai Preda"
Apr 2015

58216 Posts

Quote:
 Originally Posted by R. Gerbicz When you are loading from a precomputed cos/sin table at fft or compute these in-fly then you could reuse these values. Basically hide/halve this computation cost [or just the cost of load] if you'd compute multiple fft test at once. Ofcourse use "close" N values, so close p values [for Mersenne numbers] to have the same FFT size for the problems. Say you'd compute cos(d)*a1[i]+sin(d)*b1[i] cos(d)*a2[i]+sin(d)*b2[i] or for more than 2 tests: cos(d)*a3[i]+sin(d)*b3[i] cos(d)*a4[i]+sin(d)*b4[i] etc. Got the idea?
On the GPU, we are limited by the small number of "VGPRs" (registers) per workgroup that are available. Because we're operating at the upper limit of VGPRs, there's no much room to operate on two datasets in parallel in the same workgroup.

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