mersenneforum.org mfaktc: a CUDA program for Mersenne prefactoring
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 2020-10-20, 12:34 #3378 James Heinrich     "James Heinrich" May 2004 ex-Northern Ontario 2·37·43 Posts Tangential to this subject, I just mention for completeness: the credit given by PrimeNet and the credit displayed on mersenne.ca will likely differ when a factor is found (and bit level not completed), since primenet assumes the factor was found with prime95 (or something using an equivalent number of classes), mersenne.ca assumes the factor was found with mfaktc. On average it all balances, but specific factor "credit" may differ slightly.
2020-10-20, 12:39   #3379
axn

Jun 2003

112528 Posts

Quote:
 Originally Posted by James Heinrich since primenet assumes the factor was found with prime95
Can't it be made to assume otherwise?

2020-10-20, 12:41   #3380
James Heinrich

"James Heinrich"
May 2004
ex-Northern Ontario

2·37·43 Posts

Quote:
 Originally Posted by axn Can't it be made to assume otherwise?
It likely can, but I'll need to tread carefully with that code. I'll see how possible it is (especially since my previous fix for full-bitrange factors doesn't appear to have worked as intended).

Last fiddled with by James Heinrich on 2020-10-20 at 12:41

2020-10-21, 06:52   #3381
LaurV
Romulan Interpreter

Jun 2011
Thailand

893210 Posts

Quote:
 Originally Posted by kriesel edit: But interestingly, shows full credit
[offtopic]
[/offtopic]

Last fiddled with by LaurV on 2020-10-21 at 06:53 Reason: spacing

 2020-10-21, 07:59 #3382 kriesel     "TF79LL86GIMPS96gpu17" Mar 2017 US midwest 10010011001112 Posts Compare other recent 74-75 bit factor-found credits given, to the most recent one, and 75-76 to the proper 67.1 GhzD credit for completing the bit level. Note that had they been performed with StopAfterFactor=2 (finish the class), reduced credit would have been appropriate, and the listings here would include asterisks. These TF were all done with StopAfterFactor=1 (finish the bit level), so no asterisks. The difference can be over 90% credit loss. The difference can be rather significant on 80-86 bit final level on large exponents. Attached Thumbnails     Last fiddled with by kriesel on 2020-10-21 at 08:21
2020-10-21, 08:26   #3383
Neutron3529

Dec 2018
China

1010002 Posts

Quote:
 Originally Posted by James Heinrich A NF result is probably what I'm looking for. Ideally I'd want to know the clockspeed the GPU was running at during the run as well, but a completed NF run is a good start. https://www.mersenne.ca/mfaktc.php#benchmark
I bought a RTX 3090.
Here's my results
results.txt
(only the last result is uploaded)

I got ~5500 GHz-d/day rather than ~5200
The exactly GPU I bought is GeForce RTX 3090 VENTUS 3X 24G OC, which could easily reach fan speed 67% and temperature 75C (with P2 348W / 350W)
a normal gpu should be ~70C. Thus I do not recomment buying that GPU even it is faster.
will test gpuowl after current progress finished.

2020-10-21, 10:01   #3384
Neutron3529

Dec 2018
China

508 Posts

Quote:
 Originally Posted by moebius Please make a short gpuowl benchmark with the exponent 77936867, so that we can directly compare the values ​​of the graphics cards, thank you. https://mersenneforum.org/showthread.php?p=558317#post558317
you're welcome.

I post the first 300k iters.
A strange thing is that my GPU does not reach 350W power limit(but reach 1965Mhz which is ~200 Mhz higher than it is in mfaktc.)

2020-10-21, 12:07   #3385
Viliam Furik

Jul 2018
Martin, Slovakia

FF16 Posts

Quote:
 Originally Posted by Neutron3529 I bought a RTX 3090. Here's my results Attachment 23580 (only the last result is uploaded) I got ~5500 GHz-d/day rather than ~5200 The exactly GPU I bought is GeForce RTX 3090 VENTUS 3X 24G OC, which could easily reach fan speed 67% and temperature 75C (with P2 348W / 350W) a normal gpu should be ~70C. Thus I do not recomment buying that GPU even it is faster. will test gpuowl after current progress finished.
Why so poor result? I get about 4900 GHzD/D with the same work. It should be at least 10000 GHzD/D for the 3090, no? It has more than double the FP32 throughput.

It is most probably one of these two reasons:
1. The shared INT32 and FP32 cores don't play nicely with mfaktc - either incompatible code or the cores not fulfilling their promise
2. Memory bottleneck

Either way, I am not satisfied with the result.

2020-10-21, 13:27   #3386
Neutron3529

Dec 2018
China

23×5 Posts

Quote:
 Originally Posted by Viliam Furik Why so poor result?
I tried some machine learning program(mxnet), find it is no different to switch the cuda architecture from sm_80 to sm_86, which should have a 2x boost.

maybe the current cuda implementation does not really works for sm_86, maybe cuda 11.2 would help.

2020-10-21, 14:32   #3387
James Heinrich

"James Heinrich"
May 2004
ex-Northern Ontario

2×37×43 Posts

Quote:
 Originally Posted by Neutron3529 I bought a RTX 3090. I got ~5500 GHz-d/day
I'd be curious to know what kind of combined throughput you get when running two instances of mfaktc simultaneously?

2020-10-21, 15:04   #3388
James Heinrich

"James Heinrich"
May 2004
ex-Northern Ontario

1100011011102 Posts

Quote:
 Originally Posted by kriesel These TF were all done with StopAfterFactor=1 (finish the bit level)
I've looked at the code again and clearly I'm missing something because I think it should be working as I intended (but clearly it isn't). It's also difficult to test because that section of code will only get processed when a new factor is submitted (my logic works fine in my test environment, but something different is happening on the server). I have added a couple of debug lines that might help me track down the problem, if you see them next time you (collective "you", anyone reading this) submit a factor please email me either a copy-paste or screenshot of the output.

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