Merry Christmas and a prime! (M50 related)

[bsquared]

Originally Posted by Prime95

I don't know. James says he fixed that. We need to find another prime to test that fix :)

I suppose we code try to code up a test case that sent it to several dummy addresses plus Aaron and myself.... Given our PHP prowess we'd probably mess that up too.

I don't know anything about PHP but couldn't you just send N separate emails? For loop?
No danger of exceeding a recipient list character limit there...

[Madpoo]

Originally Posted by airsquirrels

I’m just here to say hurrah for a (potential) new prime.

Alas I am both late to the party, and haven’t kept up with the latest overpriced NVIDIA cards so I can’t offer anything unique to the verification efforts. And since it sounds like the initial run was on CUDA, a non-GPU verification is probably best.

The original was a CPU run with Prime95 28.9 so there's my own verification run as a "just to make sure" but the official double-check would need to be a different program (i.e. mlucas, cudalucas, whatever).

ATH is doing a cudalucas run. I wouldn't personally be opposed to letting you run something if you were able to get it done quicker but at this point even a fast GPU might only finish at about the same time?

Wouldn't hurt to have someone run it with mlucas just as an extra validation. I'm not running any Linux distros at the moment and too lazy to set one up, otherwise I'd totally give that a shot.

[ewmayer]

Originally Posted by Madpoo

Wouldn't hurt to have someone run it with mlucas just as an extra validation. I'm not running any Linux distros at the moment and too lazy to set one up, otherwise I'd totally give that a shot.

ATH fired up an Mlucas run on an Amazon C5.18xlarge instance this morning, but hit avx-512 build issues with the 17.1 code and was forced to use an avx2 build as a result, got ~4 ms/iter before moving to a much cheaper C4 instance), since that also supports avx2. I sent him a patched v17.1 tarball just now, hoping to see appreciably better timings from use of avx-512, though even if so, I'm not sure he'd do the verify using that build due to the expense of running on C5.

I did some manythreaded timing tests using avx2 on David Stanfill's 32-core Xeon and the GIMPS KNL (the 2 machines I am currently using for side-by-side primality tests of F30 at FFT lengths 60M and 64M, respectively) ... getting just a smidge under 4 ms/iter there. Alas the KNL offers no faster alternative because

[1] It is severely underclocked relative to the Xeon to keep the massive die from melting;

[2] Even though the KNL has 64 physical cores and 256 logical ones vs the Xeon's 32/64, I cannot take advantage of the higher core count to make up for the lower clock speed because the parallel speedups peter out between 16 and 32 threads at the relatively small FFT length needed for the new-prime candidate. (OTOH, the large FFT lengths needed by my F30 runs take much better advantage of the high core/thread counts.)

Worst case we'll get an Mlucas verify within 72 hours - if Andreas gets some nice speedups from an avx-512 build on C5, that estimate will drop, even if I have to Paypal-bribe him the C5 run costs to get him to use that for the verify. :)

[LaurV]

Yeaaa!

How did I miss this thread? (it looked like some xmas wishes, or what? I generally read all topics...)

I keep my fingers (and toes, tongue, eyes, testicles, everything) crossed!

If you need an extra CudaLucas test, give me a PM. (no, I have no idea about the exponent, I assume I joined the game too late this time).

[ewmayer]

Update: GP2 did Mlucas 17.0 avx-512 build on c5.18xlarge, timing down to 2.9 ms/iter, we continue to play with core/threadcount params to try to reduce that further. Note this was not on the default instance of this type - in his words, a "pre-LTS (beta) version of Amazon Linux 2, which has gcc 7.2.1", compared to the gcc 6.4 of the default c5 instances, for which his timing of an avx-512 build at the same FFT length was 4 ms/iter. The latter is weird, because that's the timing ATH got using an avx2 build on the (IIRC) same instance type.

But timings weirdness seems to be the name of the game for lots of threads running on fairly exotic hardware- in my own avx2-build timing tests on David Stanfill's Xeon, I was able to get at best 4.8 ms/iter on the unloaded system, but just for giggles I redid all the timings with my big nice'd F30 run crunching away in the background, and voila! The LL-test timings dropped by 20%. Both jobs (new-prime verify at full priority, F30 test nice'd) have been running side-by-side for around 10 hours now, confirming the speedup-under-background-load is not a chimera - and even with the LL-DC consuming most of the FLOPS, the F30 run is still proceeding at ~1/3 of its normal speed. IIRC Serge Batalov ran into a similar phenomenon with his Mlucas verify of a then-new M-prime a few years back - he got permission to do it on a high-end server of the company he worked for at the time, meaning he had to put up with whatever 'real work' his colleagues were using the system for competing for cycles. And like with my run, his run was fastest when other jobs were running. It's like the NBA player who can only shoot straight when he has a defender in his face. :)

[pinhodecarlos]

Are we there yet?

[pacionet]

wow ! A new mersenne prime ?
Can we know the range?
How many hours left to finish the check?

[axn]

Originally Posted by pinhodecarlos

Are we there yet?

Originally Posted by Madpoo

32 hours to go now

That was 31 hours ago...

[pacionet]

Please update the home page with somehow of "Probably found M50!"

[Mark Rose]

Originally Posted by pacionet

wow ! A new mersenne prime ?
Can we know the range?
How many hours left to finish the check?

Madpoo should have a result in a couple of hours.

And I think people are going to be surprised by the range.

Yes, I had found a leak that has since been plugged.

[ET_]

When M50 will be announced, I will appreciate whoever decides to donate a very small part of his CPU time to help sieving for MM50

We need about 300 core days in total.