mfaktc: a CUDA program for Mersenne prefactoring

[Christenson]

IMHO, the problem with combining stages isn't bitlevels...it's time...that is, all of us like feedback that something has been completed. If it takes less than an hour, I'd tell you to combine it, otherwise, leave it separate.

Eric C.

[Christenson]

OK, I have a GTX480 with 1536 Meg of RAM...In a 25-30C room (probably 80F), per GPU-Z on Win7 64 bit, it's running no load (since I have to page back and find mfaktc0.17 to download to this machine), fans at 1575RPM, and 76C for the first GPU temperature and 70C for the second GPU temperature. Two monitors are connected, the primary through the DVI and the secondary through a DVI to VGA converter. The case is open; it's an ATX tower so the fan intakes point down right now.

Is this normal behavior for such a beast, or is it running hot?

[TheJudger]

Originally Posted by Christenson

OK, I have a GTX480 with 1536 Meg of RAM...In a 25-30C room (probably 80F), per GPU-Z on Win7 64 bit, it's running no load (since I have to page back and find mfaktc0.17 to download to this machine), fans at 1575RPM, and 76C for the first GPU temperature and 70C for the second GPU temperature. Two monitors are connected, the primary through the DVI and the secondary through a DVI to VGA converter. The case is open; it's an ATX tower so the fan intakes point down right now.

Is this normal behavior for such a beast, or is it running hot?

I would say normal. Nvidia tries to minimize temperature variation on GPU, no load => low fan speed, relative high temperature. Once you increase the load the temperature will rise to ~85-90°C (reference card/cooling) and the fan speed will be adjusted in that way the the temperature is more or less constant.

Oliver

[Xyzzy]

FWIW, under 95% load (average) our GTX570 GPUs never exceed 70°C. They typically run a little more than 65°C. The ambient temperature is (right now) about 84°F.

[davieddy]

Originally Posted by Prime95

Ah, mystery solved! I should have thought of that myself. IIRC, P-1 will find somewhere in the neighborhood of 30-40% of the factors.

Assuming YRC this suggests that TF and P-1 don't "tread on each other's toes" too much.

3 extra bits of TF will reduce the factors found by P-1 by 3/70 * 35%.
If P-1's hit rate is ~6%, does a reduction of 1.5% render it not worthwhile?

David

[Christenson]

I've started work on mfaktc-primenet. One question that has come up is as follows:
When working with Operation Billion Digits numbers, do I count them against DaysOfWorkToGet, since, strictly speaking, they aren't reportable to Primenet? I certainly don't count the OBD assignments when getting Primenet assignments that I intersperse in my OBD assignments....
When these get to the output spool file, they will have to be dropped, anyway. (They will still be in "results.txt")

[James Heinrich]

Originally Posted by ATH

Use TeamViewer http://www.teamviewer.com/ instead of remote desktop. It's free for private use, and I just connected from work to my home computer and started mfaktc.

LogMeIn is also free for private use, and mfaktc starts fine.

[Brain]

Originally Posted by TheJudger

M59715763 has a factor: 897894732457600805887
M59715763 has a factor: 947242006352100744497
found 2 factor(s) for M59715763 from 2^69 to 2^70 [mfaktc 0.18-pre1 barrett79_mul32]
Oliver

Can you already tell what we're going to expect from mfaktc 0.18?

[James Heinrich]

Originally Posted by Brain

Can you already tell what we're going to expect from mfaktc 0.18?

Hopefully I'm not breaking any NDAs

version 0.18-pre1 (2011-05-24)
- autoadjustment of SievePrimes is now less dependend on the gridsize and absolute speed. Instead of measuring the absolute (average) time waited per precessing block (grid size) now the relative time spent on waiting for the GPU is calculated. In the per-class output "avg. wait" is replaced by "CPU wait".
- in all GPU kernels the functions cmp_72() and cmp_96() are replaced by cmp_ge_72() and cmp_ge_96(). Those cmp_ge_?? only check if the first of two input numbers is greater or equal than the second number. cmp_?? checked if is is smaller, equal or greater. A small performance improvement (< 1%) is possible for all GPU kernels. This was suggested by bdot on www.mersenneforum.org. Thank you!
- added even more debug code for CHECKS_MODBASECASE. The new code did not show any issues. :)

[Christenson]

Originally Posted by James Heinrich

Hopefully I'm not breaking any NDAs

Not really....

My inspection of the diffs to 0.18-pre2(I'm supposed to be developing the Primenet part) found:
1) Handles Ctrl-C reliably
2) Slight improvement with the _ge functions mentioned above.
3) Minor code style improvement: I told him that we were scanning argv[0] (the name by which mfaktc is invoked) for arguments like -h, and he and I have both changed that in our tip revisions.

I don't know what Oliver has cooking, he seems busy ATM; I have cooking:
1) Automatic Primenet interaction using cURL and P95 code, controlled by the presence of a Use_Primenet in the config (big, may not make it this release except as a dummy)
2) Tack on [mfaktc-VERSION] to everything in results.txt, including factors found. This then makes it simple for the server to identify the work source. I'm also inclined to include the assignment key from worktodo.txt.
This is straightforward and in reach.

Longer term,
3) Move sieving from the CPU to the GPU. It takes a lot of CPU to keep the GPU fully occupied; I'd prefer if it only took a trivial amount so I can keep my CPU busy doing P-1 and LL tests.

Oliver might be thinking about multiple backup files for better reliability in the face of the inevitable system crashes.

Oliver:
Don't hold off on making your changes; mine will be small enough to integrate via diff.

[TheJudger]

Hi,

Originally Posted by Brain

Can you already tell what we're going to expect from mfaktc 0.18?

Evolution, not revolution.

Originally Posted by James Heinrich

Hopefully I'm not breaking any NDAs

You didn't sign a NDA so you can't break it. As you know I just asked you not to spread around -pre versions when I give them to you and AFAIK you didn't do. I like the open discussion here in this thread.

Originally Posted by Christenson

I don't know what Oliver has cooking, he seems busy ATM; I have cooking:
1) Automatic Primenet interaction using cURL and P95 code, controlled by the presence of a Use_Primenet in the config (big, may not make it this release except as a dummy)

Busy? A little bit, but a little bit lazy, too.
0.18-pre3: added two functions to estimate the amount of work for the current assignment and for the whole worktodo file. This will become useful once automated primenet interaction is implemented. Eric, I'll sent you this soon, I want to test it a little bit more.

Originally Posted by Christenson

Don't hold off on making your changes; mine will be small enough to integrate via diff.

Yepp, and (as allready told) putting your new functions into separate files makes it very easy.

Eric: automated primenet interaction is planned for 0.19, do you agree?

Oliver

P.S. don't ask for any timeline. It's done when it's done!