[QUOTE=TheJudger;263831]
What is the expected factor rate once P-1 has been done with reasonable B1/B2 bounds?

Oliver[/QUOTE]

That question has been excersizing several of us.

In particular, it was decided a few years ago that
it was more efficient to do P-1 before the last worthwhile
bit of TF. I wonder whether the P-1 would then
render the "last bit" not worthwhile.

Of course, you and GPUs have thrown a large spanner in the works:smile:

David

Two Netiquette crimes at once
 

[QUOTE=davieddy;263836]That question has been excersizing several of us.

In particular, it was decided a few years ago that
it was more efficient to do P-1 before the last worthwhile
bit of TF. I wonder whether the P-1 would then
render the "last bit" not worthwhile.

Of course, you and GPUs have thrown a large spanner in the works:smile:

David[/QUOTE]

(Responding to your own post and partially answering the question therein)

There is obviously little to be gained by refining "bit level" for TF
further. (Working near a Max/Min optimum).

But if the "worthwhileness"of the "last bit" was marginal, P-1
would obviously tip it over the edge.

David

[QUOTE=TheJudger;263831]...checked the exponent status of the first 4 no factor M53.xxx.xxx: all of tham had P-1 done before your TF attempt to 2^70.

What is the expected factor rate once P-1 has been done with reasonable B1/B2 bounds?[/QUOTE]

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.

[QUOTE=Prime95;263843]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.[/QUOTE]

Out of the hundreds of exponents that I've tested, I only ran a TF on exactly 1 that had a P-1 done on it beforehand, and that only consisted of 2 tests, so I'm not sure this solves the mystery. I'm now at 15 factors on 1495 tests, 1493 before a P-1.

This is all in the 76M range, and there has only been 23 P-1's done in that range, IIRC.

[QUOTE=drh;263845]I'm now at 15 factors on 1495 tests, 1493 before a P-1.[/QUOTE]

I think that's unlucky but not suspicious. Xyzzy's was worrisome because it involved 9000 tests.

[QUOTE=Prime95;263851]I think that's unlucky but not suspicious. Xyzzy's was worrisome because it involved 9000 tests.[/QUOTE]

I agree, and just to clarify, a "test" is a single bit level on an exponent, not only counting individual exponents, right? I've got 1495 "tests" on 322 exponents.

[QUOTE=Prime95;263843]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.[/QUOTE]

From a "throughput" POV, has TF on GPUs (at least temporarily) made P-1 redundant?

[QUOTE=davieddy;263864]From a "throughput" POV, has TF on GPUs (at least temporarily) made P-1 redundant?[/QUOTE]

No. Prime95 will refuse to do P-1 if a number has had so much TF done that P-1 will not be profitable.

I think we'll see a slight reduction in the B1/B2 bounds selected now that more TF is being done.

[QUOTE=Prime95;263866]No. Prime95 will refuse to do P-1 if a number has had so much TF done that P-1 will not be profitable.

I think we'll see a slight reduction in the B1/B2 bounds selected now that more TF is being done.[/QUOTE]

Hmm.

1) I think "No" meant "Yes".

2) Without fully understanding P-1, I would have thought
"reduction" meant "increase"!

David

[QUOTE=Prime95;263843]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.[/QUOTE]

Or read it here!:
[url]http://mersenneforum.org/showpost.php?p=263717&postcount=971[/url]

:devil::uncwilly::pals::leaving:

Sorry I didn't have any numbers....hoping that the extra TF will allow P-1 to look for larger factors...

Anyway, calculation about my narrow view of GIMPS rolled through my head last night...it went like this: Decrease TF cost by factor of ~128, get ~7 extra bit levels....7*~1/70 = 1/10....so 10% more exponents will have factors found, or 10% fewer will need LL and LL-D tests...looks like the big performance increase will need to be in LL, possibly by getting the CPU out of the sieving path for TF and possibly P-1. Got to work on mfaktc this week!

[QUOTE=Christenson;263872]looks like the big performance increase will need to be in LL[/QUOTE]
Just look at the [URL="http://primes.utm.edu/largest.html"]"Top Ten" primes[/URL]

How do you think the top nine were discovered?

David

PS I was wondering for a bit why the latest
discovery was attributed to "G12" when GIMPS has found 13.
I think the explanation is that Cooper and Boone found 2.

Lightning strikes...