Prime95 defaults to proof=8 for PRP-CF tests even though I have a very large disk space allocated

[techn1ciaN]

I have my Prime95 in a dumb directory that I don't use much and so gave it 100GB for proofs. Wavefront PRP selects proof=10, as expected. But — I recently started running PRP-CF instead out of interest and every test selects proof=8.


I understand that this is almost completely inconsequential because even a power-7 proof on a cofactor-size number would take trivial time to certify. But — I have to say I'm still curious why the program does not select a higher proof power for this specific type of test, when the space for one is certainly available.


I searched for "PRP cofactor proof power" but could only find unrelated posts.

[slandrum]

It's probably related to the size of exponent you are now getting, there's really no reason to generate a giant proof file, and I wouldn't worry about it. Those certs take seconds to run (minutes on older slow hardware).

[slandrum]

If you are really concerned and want to force a particular proof level, read undoc.txt and it will tell you what line to add to local.txt

[techn1ciaN]

I figured there would be something in undoc. I'll take a look.

[kriesel]

Please read and apply https://www.mersenneforum.org/showpo...64&postcount=2
Specifically, "Use an existing topic-specific thread when practical."
There are multiple existing prime95 threads, version dependent.
A moderator may choose to merge this newly created thread into an existing thread.
Please do not make extra work for the moderators.

Also, read the fine manual files; think; apply; before posting.

[techn1ciaN]

There are multiple existing prime95 threads, version dependent.

So, you're saying it would have been appropriate to post this in the "Prime95 v30.4/30.5/30.6" (I'm running 30.6b4) thread? If so, apologies; I was under the impression that the version-specific threads were strictly for testing and debugging of new features in the relevant versions and it would be incorrect to clutter them up with procedural questions.

Also, read the fine manual files ...

Of course. At the end of the day I'm only secondarily concerned with the ability to run proof=10 PRP-CF; I was more curious if there was any reason why the program doesn't select proof=10 for PRP-CF when the disk space is available, beyond the obvious "the certs are quick anyway so it's a non-concern." But I suppose not.

[Prime95]

Originally Posted by techn1ciaN

I have my Prime95 in a dumb directory that I don't use much and so gave it 100GB for proofs. Wavefront PRP selects proof=10, as expected. But — I recently started running PRP-CF instead out of interest and every test selects proof=8.

Running proof=10 on small exponents will cost more generating the proof than you will save doing the cert.

[techn1ciaN]

Originally Posted by Prime95

Running proof=10 on small exponents will cost more generating the proof than you will save doing the cert.

Thank you for the insight!


Approximately where are the cutoff points at which the optimal power goes up? Would Prime95 set proof=11 or proof=12 for a sufficiently large exponent (say, 100M-digit) if the disk space was allocated?

[Prime95]

Over 414.2M the proof power goes to 11.

[techn1ciaN]

Originally Posted by Prime95

Over 414.2M the proof power goes to 11.

OK, so it scales very slowly. Interesting.


I happen to do DC-via-PRP using GPUOwl, which of course doesn't get more nuanced than using one, pre-set proof level for every test. I didn't have the information from this thread when I was tuning my installation and set proof=10 without thinking about it. At the current DC wavefront, would it actually be more efficient to use proof=9? If yes, around what exponent should I go back to 10?


Thanks again for your insights thus far

[Prime95]

1.7M - 6.7M = 7
6.7M - 26.6M = 8
26.6M - 106.5M = 9
106.5M - 414.2M = 10
414.2M+ = 11