"Re-doing" P-1 work
 

Is no credit for P-1 factoring given if the exponent has already had P-1 factoring done on it? I have some expired exponents that had low P-1 factoring bounds, so I decided it would be best to do them again with much improved bounds before running an LL test. I took an exponent that was previously at B1=495000 and redid P-1 testing so it's at B1=390000, B2=10432500. The exponent status page shows the new bounds under history, but didn't update the P-1 row and didn't give me any credit for it. I didn't have any problem getting credit for the previous P-1 test, but I don't know if that exponent had any P-1 already done on it or not.


prime.log

[CODE][Tue Nov 25 03:51:12 2008 - ver 25.7]
Sending result to server: UID: kmd/kmd09, M29665073 completed P-1, B1=345000, B2=8711250, E=6, Wd8: FF1B54AC, AID: 4A87D0B94AC08E148BD82519560BEA9E

URL: http://v5.mersenne.org/v5server/?v=0.95&px=GIMPS&t=ar&g=6de69d06e2405f2138fc73a980eff532&k=4A87D0B94AC08E148BD82519560BEA9E&m=UID:+kmd/kmd09,+M29665073+completed+P-1,+B1=345000,+B2=8711250,+E=6,+Wd8:+FF1B54AC,+AID:+4A87D0B94AC08E148BD82519560BEA9E%0A&r=5&d=0&A=1&b=2&n=29665073&c=-1&B1=345000&B2=8711250&fftlen=1572864&ss=62701&sh=ECCE46A54DAAFAAC5B2B136B0693264D
RESPONSE:
pnErrorResult=0
pnErrorDetail=CPU credit is 0.9478 GHz-days.
==END==

PrimeNet success code with additional info:
CPU credit is 0.9478 GHz-days.
[Tue Nov 25 22:16:28 2008 - ver 25.7]
Sending result to server: UID: kmd/kmd09, M33053023 completed P-1, B1=390000, B2=10432500, E=6, Wd8: 579DDD05, AID: 2D0DB9F00992B6626C7572116618F532

URL: http://v5.mersenne.org/v5server/?v=0.95&px=GIMPS&t=ar&g=6de69d06e2405f2138fc73a980eff532&k=2D0DB9F00992B6626C7572116618F532&m=UID:+kmd/kmd09,+M33053023+completed+P-1,+B1=390000,+B2=10432500,+E=6,+Wd8:+579DDD05,+AID:+2D0DB9F00992B6626C7572116618F532%0A&r=5&d=0&A=1&b=2&n=33053023&c=-1&B1=390000&B2=10432500&fftlen=1835008&ss=44975&sh=92BEDB4B0268711BD3A138333905C8BA
RESPONSE:
pnErrorResult=0
pnErrorDetail=SUCCESS
==END==[/CODE]

From my experience and some other posts on the forum I think you get credit if both your bounds are higher than the previous ones. When I have to LL test an exponent for which the previous P-1 bounds are low I use a "Pfactor=1,2,exponent,-1,HowFarFactored,4" workunit on a v24 client. (V24 because of the memory problems of v25 that is unable to use more than 903 MB out if 8192 MB.) I am under the impression that one gets to much credit : it should be 'credit for the P-1 work just returned' minus 'credit for P-1 work to the previous bounds' but I get the credit I would earn if no P-1 factoring had been done before.

Jacob

[quote=Kevin;150755]I took an exponent that was previously at B1=495000 and redid P-1 testing so it's at B1=390000, B2=10432500.[/quote]Jacob's [I]almost[/I] right about higher bounds: the actual P-1 ranking algorithm is that highest B1 is first, then only if there are multiple results with that same highest B1 is B2 considered. As long as the ranking is one-dimensional according only to the B1/B2 bounds, that's the way it has to be. So, unfortunately, your B1=390000, B2=10432500 result was not considered an extension past the previous B1=495000 result, ranked by a single-dimensional measure of deepest P-1 done so far.

Even though your search may have had a higher probability of finding a factor than the first search, the way the database ranks P-1 results does not use a factor-probability factor or formula.

If P-1 search depth were portrayed two-dimensionally, it would be possible to represent the combined work done on your exponent by a superposition of a rectangle from x-y coordinates (0,0) to the diagonally opposite corner of (495000,495000) and another rectangle from (0,0) to a corner at (390000, 10432500), with sides parallel to the coordinate axes in each case. The resulting six-sided figure with corners at (0,0), (495000,0), (495000,495000), (390000,495000), (390000,10432500) and (0,10432500) would be a more informative way to represent the portion of P-1 search space that had been covered.

(Technical complications: There'd really need to be shading of the portion above y=495000 because your stage 2 would have found a factor there only if it were the [i]only[/i] factor in that region. Then if Brent-Suyama had been used, there'd have to be a cross-hatched and shaded rectangle stretching from (0,10432500) to (390000, some-multiple-of-10432500) in addition. But they're beyond the scope of this thread.)

The way the highest P-1 limit is displayed now is an ordered number pair of (the highest B1, the highest B2 done [I]with that highest B1[/I]).

[quote]The exponent status page shows the new bounds under history, but didn't update the P-1 row and didn't give me any credit for it.[/quote](* sigh *) Tsk, tsk. The sad outcome of 1-D projection display of a 2-D truth, like a dimension-lower Mercator projection for P-1 results. (* sigh *) :sad: