v19 pre-release discussion

[kriesel]

Originally Posted by ewmayer

I am doing final shakedown tests of the v19 beta release on the hardware available to me. Since the fellow who physically hosted the GIMPS KNL workstation has gone AWOL, I could use remote access to a Skylake-X system running Linux in order to test the new PRP+Gerbicz code under avx-512.

Sorry, can't help you with that, since I don't own any avx512-capable hardware yet, unless I occasionally get access to one via Colab.

But.
https://www.mersenneforum.org/mayer/README.html#news
says

Recent News: v19 released
but contains no contents or links relevant to V19.
Don't tease us like that!

[henryzz]

Originally Posted by ewmayer

I am doing final shakedown tests of the v19 beta release on the hardware available to me. Since the fellow who physically hosted the GIMPS KNL workstation has gone AWOL, I could use remote access to a Skylake-X system running Linux in order to test the new PRP+Gerbicz code under avx-512.

Could Amazon's cloud cpus be an option?

[axn]

Originally Posted by kriesel

unless I occasionally get access to one via Colab.

I get one within less than 5 tries 90% of the time. Of course, I'm just using CPU-only notebook.

[ewmayer]

Originally Posted by kriesel

Sorry, can't help you with that, since I don't own any avx512-capable hardware yet, unless I occasionally get access to one via Colab.

But.
https://www.mersenneforum.org/mayer/README.html#news
says

Recent News: v19 released
but contains no contents or links relevant to V19.
Don't tease us like that!

Ha - one of my early v19-oriented edits in my local version of the README.html sneaked into an edit I uploaded with material on the Android-phone battery-blowup problems I had. The actual section pointed to by that 'v19' link still says v18, so will leave as is, since it's not like I have millions of confused users burning up the interwebs due to the typo.

Originally Posted by henryzz

Could Amazon's cloud cpus be an option?

Fellow forumite Laurent Desnogues has access to an avx-512 machine via work and has kindly been helping out. Alas, no remote access, so the debug is proceeding slowly. But I still have at least a week of further shakedown testing on the ARM, sse2 and avx2 builds of the current v19 code I need to do, as well as lots of edits needed to the above-mentioned readme page, so no breakneck speed needed on the avx-512 front, since the debug issue Laurent's build turned up has been localized to a small section of new code, where I figured any such SIMD-version-related bugs would occur.

[ET_]

Originally Posted by ewmayer

Ha - one of my early v19-oriented edits in my local version of the README.html sneaked into an edit I uploaded with material on the Android-phone battery-blowup problems I had. The actual section pointed to by that 'v19' link still says v18, so will leave as is, since it's not like I have millions of confused users burning up the interwebs due to the typo.



Fellow forumite Laurent Desnogues has access to an avx-512 machine via work and has kindly been helping out. Alas, no remote access, so the debug is proceeding slowly. But I still have at least a week of further shakedown testing on the ARM, sse2 and avx2 builds of the current v19 code I need to do, as well as lots of edits needed to the above-mentioned readme page, so no breakneck speed needed on the avx-512 front, since the debug issue Laurent's build turned up has been localized to a small section of new code, where I figured any such SIMD-version-related bugs would occur.

Please, keep us informed about what the ARM version can (and can't) do...

[ewmayer]

Luigi, the ARM version will have the same PRP support as the rest, I currently have one PRP-DC running on my Intel Haswell box and another on one of my Samsung S7 Android phones as part of my pre-release testing. The ARM run will need ~3 months, but I will not hold up the release waiting for it to finish, rather I will consider a successful Haswell PRP-DC run sufficient as a correctness test, since I have done enough short-length tests on my various ARM and Intel hardware to assure myself that the various builds are producing matching results. I know you are keen to see PRP-C support ... I am hopeful that with the basic PRP stuff in place adding PRP-C functionality will be less of an effort, but that remains to be seen.

In the meantime, just finished analyzing and working around a subtle bit of regexp weirdness was causing first-time-PRP-assignment-fetch to fail in my v19 primenet.py script, at the same time that PRP-DC-fetch was working fine. Laurent sent me some avx-512 debug data yesterday which will hopefully allow me to pin down the bug in the new 2-input-FFT-mul code there, and my check of the PRP-DC on my Haswell this morning showed that said run got hit by a data-corruption glitch - my Haswell is prone to these, roughly once per week under full all-cores load - and that caused the retry-on-error logic in the code to go into an infinite loop, so another bug to track down. Back to the salt mines!