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 2003-10-16, 13:07 #1 TauCeti     Mar 2003 Braunschweig, Germany E216 Posts Is TF from 2^64 to 2^65 using SSE2? I know that whatsnew.txt states for Version 22.7 : "Trial factoring above 2^64 on a P4 now uses the SSE2 instructions." I just want to confirm here, that this is really the case, because i get some strange results using Hyperthreading simultanously with one LL-instance and one TF-instance. Actually, between 2^64 and 2^65 i get a net-throughput increase of roughly 44% using HT compared to 20% between 2^63 and 2^64. Before i started to test HT, i expected a performance _decrease_, once TF and LL both start using SSE2. If 2^65 on P4 is really SSE2, then more on this topic from me in another thread in the hardware-section later... Tau
 2003-10-16, 15:30 #2 TauCeti     Mar 2003 Braunschweig, Germany 2×113 Posts ... hmmm, my strange results are still there but now i have tested a 2^67 TF with the same result and i am pretty sure SSE2 is used there. More in the hardware section... Tau
 2003-10-16, 22:05 #3 Prime95 P90 years forever!     Aug 2002 Yeehaw, FL 2×4,079 Posts The FFT is using floating point SSE2 instructions. Trial factoring is using the integer SSE2 instructions. It makes sense that HT would benefit in this scenario.
 2003-10-17, 06:30 #4 TauCeti     Mar 2003 Braunschweig, Germany 2×113 Posts Thanks for the explanation. Maybe i really shold try to understand SSE2 in detail So - assuming for the sake of the argument - that only one HT-machine alone participates in GIMPS, would it not improve overall GIMPS throughput if HT-Users could choose in the client to use a different table for the TF-limits because in: factoring_cost < chance_of_finding_factor * 2 * primality_test_cost the factoring cost is reduced by about 40% using HT? Tau

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