20090909, 23:52  #1 
(loop (#_fork))
Feb 2006
Cambridge, England
2×7×461 Posts 
A computation worthy of the name
I have spent a little while figuring out parameter choice for this; here is the polynomial for 2^941  1:
Code:
n: 2468815427808777830385945175570959888649322954010151512577652841207233127175594988619285951813249353482864131674513502872982111245757912252275917421142241044267118542381889815949472721865947896251559297022100274282885756253947868389157090816092206938192397903861973556952725044519 c6: 1 c0: 2 Y0: 182687704666362864775460604089535377456991567872 Y1: 1 skew: 1.12 rlim: 300000000 alim: 250000000 lpbr: 32 lpba: 32 mfbr: 64 mfba: 64 rlambda: 2.6 alambda: 2.6 Each CPUminute produces about forty relations; fifteen million minutes is thirty years. This job would take a day even on one of the prideoftheNationalLabs supercomputers; I'll need all the help I can cajole. The final parts of the job will take me about a season on a reasonably fast Core i7 system. RESERVATIONS CLOSED 24/11 RESERVATIONS 10/9 andi47 5051 A+R (A side done 30/10, R side partially handed over to fivemack and done 13/11) 10/9 bsquared 5161 A+R done 29/9 10/9 fivemack 6167 A+R done 25/10 (slowed by uploading issues) 10/9 batalov 6769 A+R done 29/9 01/10 bsquared 6974 A+R done 11/10 13/10 J.F. 7475 A+R done 22/11 13/10 bsquared 7580 A+R done 26/10 15/10 fivemack 8086 A+R done 13/11 22/10 frmky pp NFS@home 8690 A+R done 11/11 24/10 frmky pp NFS@home 90100 A+R done 11/11 30/10 bsquared 100102 A+R done 06/11 08/11 fivemack 102107 A+R done 24/11 13/11 bsquared 107110 A+R 97.5%done 19/11, finished 23/11 10/9 bdodson 110190 A+R done 20/11 17/11 bdodson 190200 A+R 16/11 NFS@home 200225R RESULTS 18/09 batalov 6768R 2,122,258r in 2.0Msec PhenomII/3000 22/09 batalov 6768A 2,156,943r in 2.0Msec PhenomII/3000 25/09 fivemack 6162A+R 4,340,480r in 5.3Msec various systems 26/09 batalov 6869A 2,137,457r in 2.0Msec PhenomII/3000 29/09 batalov 6869R 2,118,321r (presumably in 2.0Msec PhenomII/3000) 29/09 bsquared 5161A+R; 43,716,577r in 61.1Msec k8/2000. 06/10 fivemack 6465A+R; 4,300,156r in 5.6Mtsec on eight threads of i7@2800MHz 11/10 bsquared 6974A+R; 21,206,954r in 31.2Msec k8/2000 (ran filtering job) 13/10 fivemack 6364A+R; 4,307,838r in 5.0Msec various systems 13/10 fivemack 6263A+R; 4,313,909r in 4.9Msec C2/2400 15/10 fivemack 6566A+R; 4,309,003r in 5.6Mtsec on eight threads of i7@2800MHz 25/10 fivemack 8182A+R; 4,172,590r in 2.45Msec K10/2500 + 2.64Msec C2/2400 25/10 fivemack 6667A+R; 4,296,209r in 5.05Msec various systems 26/10 bsquared 7580A+R; 20,068,462 relations in 30.6Msec k8/2000 27/10 bdodson 110150R; 78,785,145 relations 28/10 fivemack 8081A; 2077128 relations in 2.7Msec various systems 28/10 bdodson 150170R; 37,937,272 relations (ran filtering job) 30/10 andi47 5051A; 2,265,218 relations 02/11 fivemack 8081R; 2,095,566 relations in 3.1Msec various systems 02/11 fivemack 8283A+R; 4,162,666 relations in (a)2.56Msec K10/2500 + (r)2.45Msec C2/2400 04/11 fivemack 8384A+R; 4,149,546 relations in (a)2.82Mtsec i7/2800 + (r)2.76Mtsec i7/2800  241 hours realtime 06/11 bsquared 100102A+R; 8,076,444 relations 06/11 bdodson 170190R; 35,163,889 relations 06/11 bdodson 110130A; 38,603,445 relations 10/11 fivemack 8485A: 2,062,050 relations in 2.84Msec various systems 10/11 fivemack 8485R: 2,074,375 relations in 2.43Msec K10/2500 11/11 nfs@home 86100R: 28,995,972 relations 11/11 nfs@home 86100A: 28,868,800 relations 13/11 fivemack 8586A+R; 4,155,760 relations in (a)2.86Mtsec i7/2800 + (r)2.77Mtsec i7/2800  204 hours realtime (ran filtering job: 35.3 megacycles) 13/11 andi47 5050.2R + fivemack 50.251R; 2,153,725 relations 13/11 bdodson 130170A: 72,248,902 relations (ran filtering job; 28.1M matrix) 17/11 fivemack 102103A+R: (a) 2,001,779rel in 2.55Msec C2/2400 (r) 2,038,855rel in 2.47Msec K10/2500 18/11 fivemack 104105A+R: (a) 1,981,674rel (r) 2,030,985rel (various systems) 19/11 bsquared 107110A+R (97.5% done) 11,709,149 rel; last relations collected 23/11 20/11 bdodson 170190A: 35,387,263 rel 22/11 fivemack 103104A+R: (a) 1,988,386rel in 2.82Mtsec i7/2800 + (r) 2,034,560 rel in 2.78Msec i7/2800  204 hours realtime 22/11 J.F. 7475A+R: 4,197,092 rel, 5.02Msec runtime 23/11 bdodson 190200R + patches from 160A and 180R: 18,329,135 + 1,328,828 + 1,883,125 rels 24/11 fivemack 105106A+R: (a) 1,988,962 rel in 2.60Msec K10/2500 + (r) 2,026,728 rel in 2.46Msec C2/2400 24/11 fivemack 106107A+R: (a) 1,950,983 rel in 2.69Msec various + (r) 2,024,601 rel in 2.45Msec various Last fiddled with by fivemack on 20091124 at 20:39 
20090909, 23:53  #2 
(loop (#_fork))
Feb 2006
Cambridge, England
2·7·461 Posts 
Sieving yields
measured over a 1k range and extrapolated idealwise

20090909, 23:54  #3 
(loop (#_fork))
Feb 2006
Cambridge, England
2·7·461 Posts 
Memory usage
wouldn't it be nice to attach multiple files to the same post?

20090909, 23:54  #4 
(loop (#_fork))
Feb 2006
Cambridge, England
1100100110110_{2} Posts 
How long it takes
Looks like about three CPUdays for a 100k range, so this is a factor three or so slower than 2^8771 was

20090910, 05:01  #5 
Oct 2004
Austria
4662_{8} Posts 
I assume that this one will run for several months, so there might be enough time to run it over various weekends (even on a system with "only" 2 GB), so I will reserve a chunk which needs least memory (due to necessarily low factorbase bound(s)):
reserving 50M  51M (r+a) I will run it on only one core of a Core 2 Duo (Win XP 32 bit, 1 GB RAM; testing needed ~800MB Ram and 1.6 GB virtual memory) and will run only when I am out of office (weekends and so, with the 2nd core doing a lowmemoryjob like GIMPS TF'ing), so it might take quite a while. If it turns out that it does too much swapping (i.e. slowly murdering the harddisk), I might stop and unreserve somewhere in the middle. Edit: I will start in ~1 week to 10 days, when my current c153 (2,1766M) finishes sieving (this one was at ~45.1M rels, 39.7M unique, when I did a filtering run on thuesday). Last fiddled with by Andi47 on 20090910 at 05:33 
20090910, 06:57  #6 
Oct 2004
Austria
2·17·73 Posts 
Suggestion: How about rlim=268435455 (2^281)? This might be somewhat more memory efficient.
fivemack: Yes, quite possibly; try it if you want and report if it saves anything perceptible. Last fiddled with by fivemack on 20090910 at 08:43 
20090910, 08:35  #7 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
10,093 Posts 
Damned if I ever passed a good 1% stake in a computation worthy of the name! Count me in for the treacherous ranges 6769M a+r.
_____ I'll stand under the bridge I laid my hands on. 
20090910, 14:18  #8 
"Ben"
Feb 2007
23×163 Posts 
Looks like the university's 36 k8/1400 cpus are not available now, but happily 40 k8/2000 cpus are... so I'll take 51M61M A+R.
 ben. 
20090910, 16:04  #9  
Oct 2004
Austria
2482_{10} Posts 
Quote:
As I said, I will start the "productive" run in approx. 710 days, namely when 2,1766M finished sieving. 

20090910, 16:05  #10  
Jun 2005
lehigh.edu
2^{10} Posts 
Quote:
two of our marvelous seven firsts finish (1642L should factor today, the c169 gnfs on Friday, 5p346 should finish sieving sometime today, 11p233 will start today, last one is 5m347). Bruce 

20090910, 17:24  #11 
Oct 2004
Austria
2·17·73 Posts 
benchmark
sieving with 16e on the a side from Q=50M to 50M+200 on a P4 (win XP, 32 bit)
rlim = 300M max. mem = 874 MB virtual mem. = 1.749 MB total yield: 68, q=50000201 (3.13947 sec/rel) rlim=2^281: max. mem = 825.7 MB virtual mem = 1.666 MB total yield: 66, q=50000201 (3.13068 sec/rel) (can please someone verify the timing, hence mine was done on a somewhat busy P4?) 
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