mersenne.ca "GPU72" target

[Andrew Usher]

There seems to be no good reason for that change; 'balanced' would be called that for a reason. As your bounds clearly aren't based on 30.8 (and have little resemblance to those chosen by it), test results should have been from an earlier version - and as Kriesel points out, programs other than prime95 have not implemented the new algorithm at all.

It may be true for the casual user that he should always let the program select bounds for him, but for more mathematically sophisticated people that's not reasonable and sounds condescending.

[James Heinrich]

Originally Posted by Andrew Usher

As your bounds clearly aren't based on 30.8

The bounds algorithm is my simplified PHP implementation of the one written by Mihai for gpuowl, and adopted by George for Prime95 v30.(?) I was going to say v30.8, but perhaps it was v30.7, I don't really remember.
edit: it must be v30.7, my comments say I converted the code on 2020-Aug-10. So maybe perhaps I need to dig into the v30.8 code and see if I can figure out a new algorithm. Not looking forward to that.
edit2: the top of pm1prob.c shows:

/* Copied with permission from https://github.com/preda/gpuowl/pm1 on 2020-08-11 */
/* Code courtesy of Mihai Preda */
/* Modified to work on non-Mersennes and P+1 factoring (variable takeAwaybits) */

Originally Posted by Andrew Usher

It may be true for the casual user that he should always let the program select bounds for him, but for more mathematically sophisticated people that's not reasonable and sounds condescending.

Presumably those mathematically sophisticated people (of which I most certainly am not one) know better and can make their own judgement calls about what bounds to select in their use-case.

[Andrew Usher]

Simply reverting to the old 'GPU72' numbers would be fine. The numbers currently posted can't possibly be correct for 1 test saved, because (except the smallest exponents) the ratio (P-1 GHz-days)/(PRP GHz-days) exceeds the factor probability (since this is pre-30.8, GHz-days are a valid measure). If your algorithm is correctly using just 1 test saved, then its 'maximum' outputs are intentionally overkill.

By keeping those values up, you are advising people to do wasteful P-1, by either using both bounds directly, or using B1 and allowing prime95 to determine the optimal B2 for it.

[James Heinrich]

Originally Posted by Andrew Usher

Simply reverting to the old 'GPU72' numbers would be fine

I have reverted the Target B1/B2 to what GPU72 line showed before.

In the longer time I'll try to get the v30.8 bounds selection code ported to PHP, but that may take a while.

[Andrew Usher]

Thanks. This really belongs more in the mersenne.ca forum, where I've just posted about a different (low-priority) issue with your site.

[chalsall]

Originally Posted by James Heinrich

I have decided to remove the "PrimeNet" line entirely, since both the TF level and B1/B2 are irrelevant. I now have "Actual" and "Target", and the "Difference" line makes more sense than it did before.

Channeling my Mr. Burns... "Excellent...

Originally Posted by James Heinrich

It's easy to ignore inconsistencies because "it's always been that way", so thanks chalsall for pointing it out.

Thanks for the call-out. But, really, this is all your work... Seriously. 8-) To give thanks where thanks are due...

When GPU72 first started we had no idea what we were doing, other than feeding compute questions to answer. This was leveraging on early work Oliver (TheJudger) had done as a proof of concept (which then scaled nicely) using nVidia CUDA.

James quickly stepped in, and did a ***deep-dive*** of the optimal economic cross-over points we were actually working with. As a function of each GPU make and model. With a huge amount of peer review.

This is just one example of the reports that informed us. Thus, I think it is completely appropriate for the nomenclature change on MERSENNE.CA.

P.S. I sometimes go over the top with compliments. But few appreciate just how much talent, dedication, and *years* of work are involved with maintaining the longest running Distributed Computing project.

P.P.S. The BH3 Christmas Party was this evening. Good tunes. Good friends. Serious conversations. It was nice getting back out into the "Big Blue Room"...

[chalsall]

Originally Posted by James Heinrich

In the longer time I'll try to get the v30.8 bounds selection code ported to PHP, but that may take a while.

No good deed goes unpunished... 9^)