5^421-1 sieving (reservations closed)

fivemack · 2008-07-21, 17:30

The .poly file is

Code:

n: 856747567165509732120757534754047466186338557004916269612235956443230634437193149247989845404816349224130750819510131856088353227722964229252203600736528648205287332264407802189199
skew: 1287906.31
c5: 5767280580
c4: -12525357190853198
c3: -23832471548163085528052
c2: 16917954271985164657592650551
c1: 14831413561315809659995278076458170
c0: -5682335232801110703624206006414844672400
Y1: 46531574816134967669
Y0: -10823715308709192191932199683059669
lpbr: 31
lpba: 32
mfbr: 62
mfba: 64
rlambda: 2.6
alambda: 2.6
rlim: 80000000
alim: 150000000

The rational-side yield is much lower than the algebraic-side yield, so I think it makes sense to sieve on the algebraic side only. 31-bit rational primes give something like 40% more relations per Q and need about 20% more relations than 30-bit rational primes would; the R and A factor-base limits are about right.

A million-Q range should take about ten CPU-days to sieve (using the 64-bit ggnfs executable on a Core2/2400) and produce a bit over a million relations; we want about 400 million, so there's lots of reservation space. Use ggnfs-lasieve4I15e; the jobs take about ten minutes to get started, and use 900M of virtual and 400M of physical memory (450M under Windows).

(12 Sep 2008)Please make reservations in the 40M-80M region before carrying on from 328M
(24 Sep 2008) Not taking any more reservations; this lot should suffice!
Reservations

Code:

bsquared   40M-53M (done 30/09)
batalov    53M-55M (done 27/09)
bsquared   55M-75M (done 25/09)
fivemack   75M-90M (done 26/09)
smh        90M-100M
fivemack   100M-120M (done 14/09)
smh        120M-124M (done 07/09)
fivemack   124M-130M (done 02/09)
smh        130M-136M (done 31/08)
andi47     136M-140M
smh        140M-145M (done 07/08)
frmky      145M-150M (done 02/08)
fivemack   150M-162M (done 02/08)
FactorEyes 162M-170M (done 12/09)
andi47     170.03M-172.27M (done 01/09)
fivemack   172.27M-174M (done 13/09)
Batalov    174M-180M (done 19/09)
bsquared   180M-200M (done 31/07)
bsquared   200M-220M (done 08/08)
fivemack   220M-236M (done 18/08)
bsquared   236M-256M (done 18/08)
fivemack   256M-268M (done 30/08)
bsquared   268M-288M (done 27/08)
bsquared   288M-308M (done 10/09)
bsquared   308M-328M (done 19/09)
bsquared   328M-338M (done 24/09)
fivemack   338M-340M (done 29/09)

Ranges that I have

Code:

40M-92M 100M-136M 140M-340M

jasonp · 2008-07-21, 19:20

Quote:

Originally Posted by fivemack

A million-Q range should take about ten CPU-days to sieve and produce a bit over a million relations; we want about 400 million, so there's lots of reservation space

With these parameters, your job will be the first test of msieve with 32-bit large primes. The entire library is supposedly '32-bit clean', but I expect postprocessing trouble commensurate with the epic size of this job. Did your 8G machine ever run the lanczos solver reliably?

fivemack · 2008-07-21, 21:36

I managed to run a small job (29-bit large primes) to completion with four threads on that 8G machine at one point, but I've had no luck getting the machine to misbehave on anything other than msieve, or reliably enough to be diagnosed when running msieve. So I'm contemplating getting another machine; I've got the money in the bank, but I'll wait until the sieving has finished in the hope that Nehalem exists by then.

[there's a 16GB 8-core Penryn machine at work, but it's the fileserver, and running jobs that use most of it for months will not make me popular]

Andi47 · 2008-07-22, 04:33

Quote:

Originally Posted by fivemack

So I'm contemplating getting another machine; I've got the money in the bank, but I'll wait until the sieving has finished in the hope that Nehalem exists by then.

[there's a 16GB 8-core Penryn machine at work, but it's the fileserver, and running jobs that use most of it for months will not make me popular]

Hmmm... The Nehalem - Lynnfield processor has been postponed from Q1 2009 to Q3 2009 since I looked the last time (a few months ago). The Bloomfield processor (more powerful but it consumes more energy - 130 W) is due at Oct. 2008.

Edit: For a longer-term test (a few days up to a few weeks) on your big machine you can possibly double-check M100,000,007 using prime95 version 25.6 (multithreaded). There are several interim residues posted in this thread, beginning at ~iteration #12M, and further every few million iterations.

Andi47 · 2008-07-22, 09:38

Quote:

Originally Posted by fivemack

Use gnfs-lasieve4I15e; the jobs take about ten minutes to get started, and use 900M of virtual and 400M of physical memory.

in windows it takes ~450MB of physical memory.

FactorEyes · 2008-07-23, 00:00

If we assume that 11 volunteer sievers step up with an average of 36 million Q values apiece, that's 1 core-year (=360 core-days) per volunteer, to get the sieving done. I'm assuming all have the 64-bit optimized 4I5e running, which is optimistic. At 4 cores per volunteer, that's 3 months' running time.

Obviously there are the odd free cycles from clusters, which will likely do 1/3 of the work, so we're down to, say, 2 solid months from each volunteer with 4 cores available.

Over the next 45 days I can easily finish my commitment of 8 million Q values, and I'll toss in more if they're needed, but I doubt I could sieve more than 20 million Q in six months. Give me a year, and I could toss in at least 30 million.

It seems as if 4-5 months of sieving is the bare minimum here, unless there is substantial enthusiasm for this project. I think it's worth doing, especially since the linear algebra will push things a bit.

I'm trying to get an idea of how to prioritize my current stack of fun integers. Do my ideas about the timeline sound about right?

fivemack · 2008-07-23, 07:38

Quote:

Originally Posted by FactorEyes

If we assume that 11 volunteer sievers step up with an average of 36 million Q values apiece, that's 1 core-year (=360 core-days) per volunteer, to get the sieving done. I'm assuming all have the 64-bit optimized 4I5e running, which is optimistic. At 4 cores per volunteer, that's 3 months' running time.

Obviously there are the odd free cycles from clusters, which will likely do 1/3 of the work, so we're down to, say, 2 solid months from each volunteer with 4 cores available.

That's much the same timescale that I was anticipating, though I suspect the average cores per volunteer is probably a bit over four given that there are people who sieve using idle cycles at work. I wouldn't recommend anyone making a reservation now that takes more than about six weeks to finish; I've spoken for a million per available core and will get another million per core as and when those finish, I think that's about the right strategy though obviously it's worth reserving more if you know you want the machine to run unattended over a summer vacation.

Quote:

It seems as if 4-5 months of sieving is the bare minimum here, unless there is substantial enthusiasm for this project. I think it's worth doing, especially since the linear algebra will push things a bit.

There seems to be reasonable enthusiasm - bsquared has a lot of compute resources, and it's only been 36 hours since I put the message up - though the people with the enormous clusters are committed to a long list of large SNFS jobs.

Andi47 · 2008-07-23, 10:10

Quote:

Originally Posted by fivemack

...obviously it's worth reserving more if you know you want the machine to run unattended over a summer vacation.

That's exactly what I do: I will be on summer vacation the whole august, and so I reserved a range which should be finished near the end of august / beginning of september. (I hope it's ok when I don't finish before the 1st week of september)

Shortly before I leave for vacation I will reserve a second range (for the second thread of the core2duo). I can't start this right now, because it would take ~90-92% of the available memory and thus will make it nearly impossible to work at this computer.

bsquared · 2008-07-23, 19:41

To be fair, I personally have very small compute resources; one lowly Athlon 4200+ X2 to be precise. The compute resources I have *access* to are quite a bit more substantial. Which reminds me that I'd like to make sure Sam Wagstaff is informed of that fact so the various universities can be acknowledged in the cunningham book. Hopefully that's possible.

I'm also grateful to Tom for organizing efforts like these, otherwise said resouces would be woefully underutilized. I can manage to launch a few scripts to aid projects which have already been skillfully researched and organized but a 3 year old and a 5 month old tend to otherwise occupy any time not spent working or sleeping :)

Looking forward to seeing this one through!

- ben.

Batalov · 2008-07-26, 04:43

Quote:

Originally Posted by fivemack

A million-Q range should take about ten CPU-days to sieve (using the 64-bit ggnfs executable on a Core2/2400) and produce a bit over a million relations

I get about 1.36M rels from my interval (I guess you are counting the future non-redundant rels).
The file will be about 150Mb in size, and after "bzip2 -9", 72Mb.
Please remind where we should upload them and what's the secret city this time.

Serge

fivemack · 2008-07-26, 20:45

Code:

ftp chiark.greenend.org.uk
user: anonymous pass: your email address
cd special/twomack-relations/malmo
put 150M-151M.bz2

I have moved across the Oresund from Denmark to Sweden for my secret city this time.

2008-07-23, 00:00	#6
FactorEyes Oct 2006 vomit_frame_pointer 2³·3²·5 Posts	How long for the seiving on this one? If we assume that 11 volunteer sievers step up with an average of 36 million Q values apiece, that's 1 core-year (=360 core-days) per volunteer, to get the sieving done. I'm assuming all have the 64-bit optimized 4I5e running, which is optimistic. At 4 cores per volunteer, that's 3 months' running time. Obviously there are the odd free cycles from clusters, which will likely do 1/3 of the work, so we're down to, say, 2 solid months from each volunteer with 4 cores available. Over the next 45 days I can easily finish my commitment of 8 million Q values, and I'll toss in more if they're needed, but I doubt I could sieve more than 20 million Q in six months. Give me a year, and I could toss in at least 30 million. It seems as if 4-5 months of sieving is the bare minimum here, unless there is substantial enthusiasm for this project. I think it's worth doing, especially since the linear algebra will push things a bit. I'm trying to get an idea of how to prioritize my current stack of fun integers. Do my ideas about the timeline sound about right?

2008-07-26, 20:45	#11
fivemack (loop (#_fork)) Feb 2006 Cambridge, England 2·7·461 Posts	Code: ftp chiark.greenend.org.uk user: anonymous pass: your email address cd special/twomack-relations/malmo put 150M-151M.bz2 I have moved across the Oresund from Denmark to Sweden for my secret city this time.

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2008-07-21, 21:36	#3
fivemack (loop (#_fork)) Feb 2006 Cambridge, England 6454₁₀ Posts	I managed to run a small job (29-bit large primes) to completion with four threads on that 8G machine at one point, but I've had no luck getting the machine to misbehave on anything other than msieve, or reliably enough to be diagnosed when running msieve. So I'm contemplating getting another machine; I've got the money in the bank, but I'll wait until the sieving has finished in the hope that Nehalem exists by then. [there's a 16GB 8-core Penryn machine at work, but it's the fileserver, and running jobs that use most of it for months will not make me popular]

2008-07-23, 19:41	#9
bsquared "Ben" Feb 2007 111010010100₂ Posts	To be fair, I personally have very small compute resources; one lowly Athlon 4200+ X2 to be precise. The compute resources I have access to are quite a bit more substantial. Which reminds me that I'd like to make sure Sam Wagstaff is informed of that fact so the various universities can be acknowledged in the cunningham book. Hopefully that's possible. I'm also grateful to Tom for organizing efforts like these, otherwise said resouces would be woefully underutilized. I can manage to launch a few scripts to aid projects which have already been skillfully researched and organized but a 3 year old and a 5 month old tend to otherwise occupy any time not spent working or sleeping :) Looking forward to seeing this one through! - ben.