20221115, 15:44  #12 
Jul 2009
Germany
2A0_{16} Posts 

20221115, 15:55  #13  
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
11^{2}·61 Posts 
Quote:
The quoted P1 calculations above have failed badly and early. There is no point to continuing that P1 attempt. P1 computes in stage 1, powers of 3. The red highlighted res64 = 0 shows the calculation has already failed. Also, please do not run large exponents until you get it sorted out how to run reliably. P1 has fewer error checks than PRP. If PRP fails as rapidly as you have demonstrated, so will P1. When we were young children, we did not run before crawling, then walking. Start small and carefully, methodically. Generally, for a GPU, first get it to run PRP reliably in the same version you would use P1. Then verify with P1 on a small exponent that you can find a known factor. Then again on a medium exponent. Ideally again with a test exponent (near in value to where you plan to run new work) with known factor, that will default to using the same fft length as you plan to run new work. See https://www.mersenneforum.org/showpo...8&postcount=31 for some to try to reproduce. Only after it's proven reliable, proceed to new work. Some GPUs simply are not capable, or with time become incapable, of operating at sufficient reliability. And M888888887 PRP & proof is under way by me on a Radeon VII. You will not likely finish before me. All the remaining near repdigits <1G are estimated to be finished in January or February. Please do not launch computations without an assignment. Please begin reading the reference info, in the recommended starting sequence. It is large and will take some time to get through enough to become an effective participant. You might find CUDALucas memtest or mfaktc self test helpful in sorting out what is making your GPU so errorprone. Its error rate is STARTLINGLY HIGH. Please address that first. (Or it may be defective hardware. Is it too late to return it?) Then prove it out with some ordinary small runs. Large runs need highly reliable hardware & software combinations. Do not attempt large runs on hardware/software combinations until they are proven reliable on small runs, then medium runs. And again, the best use of an RTX 4090 would be TF where it is needed. It's designed for far higher performance in low precision computation (SP) which suits TF. Even if it were perfectly reliable in DP (and it is far from that), its power cost (and purchase cost) would be higher than for a Radeon VII for the same work done. Using a 4090 for other than TF is a little like using a hammer where a screwdriver is needed. If you are determined to use that GPU for PRP and P1 despite it being relatively unsuited both by design and from initial experimental experience, consider simultaneous P1/PRP in v7.2. The P1 may still fail to find a factor that should be found for the bounds used, but V7.2's coding provides more error detection for P1 stage 1 work in progress than any v6.x, with a combination of using GECprotected powers of 3 from the PRP computations, and using the Jacobi check for their multiplication together, IIRC. V7.2 also provides much lower incremental cost of a P1 stage 1, IF you are also going to run the PRP for the same exponent in the absence of finding a factor. Or, someone else could run the P1 for you by mutual agreement. There's a forum thread for that. Last fiddled with by kriesel on 20221115 at 16:51 

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