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2022-08-07, 11:33   #89
swellman

Jun 2012

2×7×263 Posts

Quote:
 Originally Posted by bur That seems so low to me. A GNFS 160 takes about 160M raw relations, a GFNS 165 takes about 220 M when I do it with CADO using Curtis' optimized parameters. Is this a result of using very different parameters?
Different parameters and different tools, i.e. GGNFS/msieve vs CADO. Here we are using the historical trend for the recommended # of raw relations needed for msieve on a 30-bit job to form a matrix. But we can always kick up Q if the matrix won’t build at say target density = 110 in postprocessing.

~140M raw relations should be sufficient.

2022-08-07, 13:20   #90
charybdis

Apr 2020

35716 Posts

Quote:
 Originally Posted by bur That seems so low to me. A GNFS 160 takes about 160M raw relations, a GFNS 165 takes about 220 M when I do it with CADO using Curtis' optimized parameters. Is this a result of using very different parameters?
The number of relations needed is determined by the lpb bounds, not by the size of the number. Increase each lpb by 1 and you ~double the number of relations required. The mfb bounds also have an effect but it is smaller, e.g. using 3LP on one side needs maybe 20% more relations (can't remember exactly how much it is!)

 2022-08-07, 13:36 #91 VBCurtis     "Curtis" Feb 2005 Riverside, CA 156116 Posts Bur- When testing params choices on CADO, I find I need 2-3% more relations per digit for a given LP bound choice, and 70% more relations for a given input number for each increase of 1 LPB. 2% per digit adds up when we consider 10+ digit differences- a C170 on 32LP doesn't need nearly as many relations as a C185 with the same large-prime bounds (using larger lims on the C185 adds to this effect). 30LP seems really small for a C175; yield would likely double for 31LP, and 31/32 might be yet faster. Any time GGNFS yield averages below 2.5, chances are very good a larger LP choice is faster.
2022-08-07, 16:47   #92
swellman

Jun 2012

1110011000102 Posts

Quote:
 Originally Posted by VBCurtis 30LP seems really small for a C175; yield would likely double for 31LP, and 31/32 might be yet faster. Any time GGNFS yield averages below 2.5, chances are very good a larger LP choice is faster.
In test sieving I first ran this as a 31-bit job and the yield was great. Would have been a perfectly fine way to sieve this job. But the upper end for 14d is 165-170, a 15e_small at lpba/r of 30 is acceptable for a G-175, and LA takes 1-2 days vs ~a week at 31-bit (system dependent of course). If it’s suboptimal, it’s only just.

Plus it was a nice break from all the monster jobs popping up lately.

2022-08-08, 02:26   #93
VBCurtis

"Curtis"
Feb 2005
Riverside, CA

13·421 Posts

Quote:
 Originally Posted by swellman ...and LA takes 1-2 days vs ~a week at 31-bit (system dependent of course)..
I've never noticed this- my matrices seem to depend on input size much more than LP size, until I get to 32LP. I'd be quite surprised to learn that 30 vs 31 is more than 15% larger matrix, for a given input job.

 2022-08-08, 05:58 #94 bur     Aug 2020 79*6581e-4;3*2539e-3 601 Posts I see, so a lower lpb results in fewer relations to be found, but they are more "useful"? The latter would be due to there being fewer unknowns in the LA problem?
2022-08-08, 11:19   #95
charybdis

Apr 2020

32×5×19 Posts

Quote:
 Originally Posted by bur I see, so a lower lpb results in fewer relations to be found, but they are more "useful"? The latter would be due to there being fewer unknowns in the LA problem?
2^lpb is the cutoff for the size of the largest primes/ideals that can appear in relations. Increasing lpb means that you find more relations, because you're allowing larger primes. But you also need more of them to form a matrix, because you need more relations than ideals and you've increased the possible number of ideals.

 2022-08-09, 06:32 #96 bur     Aug 2020 79*6581e-4;3*2539e-3 601 Posts Ah, thanks. Then it makes sense that increasing lpb by 1 doubles the number of required relations.
2022-08-09, 14:10   #97
VBCurtis

"Curtis"
Feb 2005
Riverside, CA

13·421 Posts

Quote:
 Originally Posted by bur Ah, thanks. Then it makes sense that increasing lpb by 1 doubles the number of required relations.
It doesn't. The required number rises by ~75%.
Many test-sievers use "twice as many relations" as their metric, and decide the smaller LPB is faster when it's not. I've completed 32LP jobs with fewer than 300M raw relations, and 31/32 jobs with 200M raw relations (5*2^784-1 required 195M raw relations as a 31/32).

If we look at NFS@home logs, we see that 32LP jobs usually gather twice as many relations as 31LP jobs; however, most of the 32LP jobs are much more difficult than the typical 31LP job, and tougher jobs require more relations. For a given input number, 75% is the right number to use when going up an LPB on both sides, or 1/3 extra when trying a split e.g. 31/32 for LPB.

 2022-08-09, 14:50 #98 swellman     Jun 2012 2×7×263 Posts I’ll throw into the mix that in the past BOINC seemed to have a higher percentage of bad relations than we experience today. More raw relations were needed to reach the desired number of uniques. Definitely could and should be using lower target # raw relations these days in NFS@Home.
 2022-08-09, 15:04 #99 kruoli     "Oliver" Sep 2017 Porta Westfalica, DE 22×7×41 Posts QUEUED AS 2_849p Cullen number 849 is an SNFS 259 which is ready for sieving. Code: n: 4693178848105443588405037077689313140090059796932891656436699701239070186072495205194603374565187182301890731865258017239714606914206045688272187831509599345913577655908463514507873092467684232436697919148670185404630805130261264540325092481 skew: 3.22737 # skew by cownoise size: 259 type: snfs c6: 1 c0: 6792 Y0: -1 Y1: 2787593149816327892691964784081045188247552 rlim: 178000000 alim: 90000000 lpbr: 32 lpba: 32 mfbr: 94 mfba: 64 lss: 0 rlambda: 3.5 alambda: 2.8 To be sieved on the algebraic side (I tested all other combinations and sieving the rational side, but this one was slightly better). Test sieving blocks of 1k gave Code: Q norm. yield 20M 3755 30M 3492 50M 3148 90M 2863 130M 2643 165M 2132 200M 2111 210M 2069 Therefore I suggest sieving Q 30M-195M for 440M+ relations. I will do the LA. Last fiddled with by swellman on 2022-08-09 at 17:00

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