At 09:36 AM 1999/09/23 -0700, Paul Leyland wrote:
>Hi Ken, that's a challenging project you're proposing.
>
>I'm very nearly tempted by this one, but the 6-year run time is a bit
>daunting. In the past I've devoted months to a single factorization but
>I've no real idea what I'll be doing in six years time or what hardware I'll
>have access to.
To clarify, it is not a requirement that individual volunteers stay with
the project the full run-time of the exponents they're working on.
If/when quitting before completion, pass the intermediate file & interim
files on to those carrying on from there.
I've been hunting mersennes since 1985, so the odds are I'll stick with
it a while, barring major unexpected events.
>It's also not clear what the payback will be.
The payback is that known-results exponents in completely new territory
will be available against which any mersenne codes developed can be tested.
The odds are low, but it's a nonzero probability that a prime could be found
in the process.
>However, I've not yet completely ruled out volunteering, but need a bit more
>incentive and a bit more information. For instance, how big are the files
>I'd need to keep around, and how many for how long?
(Note: file sizes appear to be the runlength size (ie: 112K = 114,688) x 4
plus 18 bytes for v18 and 22 bytes for v19)
For v19:
Exponent FFT,K Size of 1 save
Limit file, bytes
1990000 96 393238
2323000 112 458774
2655500 128 524310
3290000 160 655382
3935000 192 786454
4598000 224 917526
5250000 256 1048598
6515000 320 1310742
7730000 384 1572886
9020000 448 1835030
10320000 512 2097174
12830000 640 2621462
15270000 768 3145750
17850000 896 3670038
20400000 1024 4194326
25330000 1280 5242902
30100000 1536 6291478
35100000 1792 7340054
40250000 2048 8388630
49900000 2560 10485782
59400000 3072 12582934
69000000 3584 14680086
79300000 4096 16777238
>Space, per se, is not a
>real problem (as long as it's not more than, say, 10Gb) but having to keep
>them safe for years means ensuring they are backed up and so forth. When we
>did RSA-155 my contribution to the relations (about 1/6 of the total) took
>800Mb when compressed but needed to be preserved only for a couple of months
>and the copies at CWI acted as my backup, and vice versa.
To work a worst case example, 79,300,000 run at InterimFiles=1000000
would leave 80 copies (79 interims & the final) x 16MB or 1.3GB.
It isn't necessary that any one person among the testing volunteers store
more than a few exponents interim file sets, unless they are running
many exponents in parallel.
>Another question: how hard are you planning to try to factor Mersenne
>numbers? With an effort you are planning, it would make sense to me to
>spend a cpu year or so trying to factor.
Right; we are factoring to the default v19 depth, enough exponents
to get at least 3 LL-testable candidates in each runlength.
>This *can* be trivially
>parallelized and I would be happy to contribute to this phase. With the
>resources I have, I can spend a PII-400 year factoring every week or two. I
>don't mind slipping in that much between my regular jobs.
Paul, I'll be sending you some candidate exponents to continue factoring to
the full depth.
Ken
Ken Kriesel, PE <[EMAIL PROTECTED]>
_________________________________________________________________
Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm
Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
