20210618, 15:27  #12  
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
5,417 Posts 
Or as I do, get a block of ~30 manual assignments for ~18 hours of a Radeon VII GPU, check the GPU72 bounds at mersenne.ca for the highest exponent in the block, and use those bounds on all of them. PrimeNet will accept those as sufficient and not reissue the P1 work. They're a bit of overkill but not too bad, not as much as gpuowl default. Checking the highest guards against the slight chance that the recommended or required bounds change midblock and the higher exponents might not get sufficient bounds applied to retire the P1 task when reported.
Occasionally (~annually?) the analysis of what are optimal bounds gets revised and so do the posted bounds there. Quote:
So, looking up in gpuowlv7.253's help output, that would be a 6M fft. Run time scales as ~p^{2.1}, so iteration time as ~p^{1.1}, but it's "stairstepped", with step changes at fft length changes. Which subversions of gpuowl v7.2 and v6.11 did you time on your RX6800XT? There are about 70 commits of v7.2, and several posted Windows builds in https://mersenneforum.org/showthread.php?t=25624; 380 commits of v6.11 and ~37 posted Windows builds, and the timing differences can be considerable on the same hardware and inputs. Last fiddled with by kriesel on 20210618 at 16:00 

20210619, 10:26  #13 
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
5417_{10} Posts 
Also, please run and submit benchmarks for your GPU as described near the top of https://www.mersenne.ca/cudalucas.php which is particularly in need of RX 6xxx benchmarks.
Last fiddled with by kriesel on 20210619 at 10:27 
20210626, 10:47  #14 
"David Kirkby"
Jan 2021
Althorne, Essex, UK
110100111_{2} Posts 
Somewhat related, although I am using mprime, is it possible, and more to the point sensible, to do stage 2 of P1, without doing stage 1, given someone else has done stage 1?
I have been assigned M103770473, which has been trialfactored to 2^76, then P1 done with both B1 and B2 = 710 000, which I believe means stage 1 has been completed, but not stage 2. The entry in worktodo.txt indicates no work will be saved doing P1 factoring, but I'm wondering if that is really true, given only the first stage has been done. I just looked at the time to do P1 on a similar sized exponent on my computer and see stage 1 takes about 30 minutes and stage 2 around an hour, so stage 2 is the more timeconsuming stage. Given the particular circumstances of this exponent and my computer * Linux running mprime. * The exponent is trialfactored to 2^76 * Stage 1 of P1 done to 710 000 by someone else. * Stage 2 not done. * My machine takes about twice as long to do stage 2 as stage 1 what's the best thing to do? I should be commencing this exponent in less than 2 hours, but I might move it further down the queue, to give more people chance to answer, as I'm aware many Americans will be asleep at moment in time. Last fiddled with by drkirkby on 20210626 at 11:00 
20210626, 11:38  #15 
"David Kirkby"
Jan 2021
Althorne, Essex, UK
110100111_{2} Posts 
Okay, I found a partial answer from undoc.txt. This will skip stage 1 in mprime
Code:
Stage1GCD=0 Code:
PRP=AID,2,103770473,1,710000,30000000,76,1 According to https://www.mersenne.ca/prob.php?exp...00&b2=30000000 those values for B1 and B2 would have a 4.13% chance of finding a factor, and use 13.3 GHz days. Given I don't need to do P1, I suspect the time would be about two thirds or that, or 8.9 GHz days. I don't suppose that those values would be optimal for finding a prime, but they might be reasonable. Dave Last fiddled with by drkirkby on 20210626 at 12:19 
20210626, 12:26  #16 
Jun 2003
2·3·7·11^{2} Posts 
You cannot continue the P1 from the previous stage 1, since you don't have the result of the stage 1. And without the result of stage 1, you can't meaningfully do stage 2. So there's no "skipping" Stage 1. You have to do both from scratch.
Is it worth it? 710k, 30m @ 76 bit has a probability of 4.1% But since we already know that previous stage 1 didn't find any factor, the incremental probability is 4.11.5 = 2.6% (1.5% is the probability with just 710k @ 76). Statistically, it is probably not worth it. But, OTOH, it is just 1.5 hours of your life  if you can live with it, go for it. BTW, Stage1GCD=0 will skip the gcd, but the gcd cost is just a few seconds, so you're not saving anything. And as explained above, I think you're working under the incorrect assumption that you could somehow skip stage 1; you can't, so this stage1gcd is a bit of a red herring. BTW 2  You don't necessarily have to use the previous B1. You could use a different value (lower or higher). So if you decide to go ahead with P1, ask P95 to generate optimal bounds for saving 1 test and go with it. 
20210626, 14:18  #17  
"David Kirkby"
Jan 2021
Althorne, Essex, UK
3^{2}×47 Posts 
Quote:
https://www.mersenne.org/various/math.php#p1_factoring it was not apparent to me that the results from stage 1 were needed for stage 2. However, given they are, and the probabilities you calculate, I will skip the P1, and just go straight for the PRP test. 

20210626, 15:08  #18  
6809 > 6502
"""""""""""""""""""
Aug 2003
101×103 Posts
9,817 Posts 
Quote:
Since this is a low Cat 0, we know that this was not a manual assignment. But, you are deciding to mess with the defaults of how PrimeNet assigned it to you. If this was assigned to me and I decided to monkey around with the assignment, and I had the kit, I would start the PRP on 1 machine (moving it ahead of the other items in the queue) and do P1 on a second machine with bounds set to have a higher chance of finding a factor. But, generally I would just leave it alone to do its thing if it is not the last 1 or 2 before a milestone. One of my slower machines had a DC assignment go from a Cat 1 to a Cat 0. I just watched the progress via my workload page and let it do its thing. The machine is in a multiuser environment and the power goes out at the facility several times a year. So that is why I watch it more than the average person would have to the average machine. 

20210626, 16:18  #19  
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
5,417 Posts 
Quote:
Please use the reference info (or in this case even a web search or wikipedia!); read, learn, understand. It's a never ending process. Beware though of the wikipedia suggestion to use a=2. For Mersenne numbers, that's very bad advice. There's no substantial obstacle to running P1 on an exponent on one worker, and PRP/GEC/proof, on the same exponent, on another worker, even on the same system, same prime95 or mprime instance, simultaneously. It speeds completion overall, by running in parallel, while gambling a bit of computing time may be lost. (The PRP progress or completion is pointless if P1 finds a factor.) For kicks, I put PFactor=0,1,2,103770473,1,76,2 on a gpuowl run on Radeon VII GPU. It will have the default 1M, 30M bounds. Stage 1 will be done in 21 minutes (from 11:23:30 US CDT). Stage 2 if needed I estimate at 21 minutes also. Please, everyone, adjust your prime95 P1 stage 2 memory limits upward from default if practical. The default 0.3GB prevents stage 2, and stage1only is inefficient. Using adequate bounds the first time is the most efficient. Last fiddled with by kriesel on 20210626 at 16:39 

20210626, 19:34  #20 
∂^{2}ω=0
Sep 2002
República de California
2×3^{2}×647 Posts 

20210626, 20:50  #21  
"David Kirkby"
Jan 2021
Althorne, Essex, UK
3^{2}·47 Posts 
Quote:
Quote:
The position in the queue only got swapped for another category 0 exponent assigned the same day. BTW, I completed a triple check of one of the LL results you listed in another thread  M57906071. No less than 7 people got assigned LL tests, with 3 results, but at least two of them now agree. 

20210626, 21:43  #22  
"David Kirkby"
Jan 2021
Althorne, Essex, UK
1A7_{16} Posts 
Quote:
https://www.neowin.net/news/gamersr...ttingcheaper/ https://www.fudzilla.com/news/graphi...ewindingdown are now indicating the prices of GPUs have peaked, and are falling, so I might look for a Radeon VII GPU soon. Although one site I looked at indicated the topend cards have fallen 1015%, whereas low/mid end cards 50%. So maybe I will wait a bit longer. I could probably get comparable performance sticking in the most expensive CPUs my workstation will take, but that would cost one hell of a lot more than a Radeon VII or two, even at todays prices. Quote:


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