Mersenne Digest V1 #685
Mersenne DigestMonday, January 31 2000Volume 01 : Number 685 -- Date: Wed, 26 Jan 2000 22:49:57 +0100 (CET) From: Henrik Olsen [EMAIL PROTECTED] Subject: RE: Mersenne: small OS setup for mprime On Wed, 26 Jan 2000, Sylvain PEREZ wrote: What I personnaly did is to install a full (but light) Windows95 system on an IomegaZip 100 disquette, plus the regular Prime95 v19. So now I only need a motherboard, an internal zip drive and some little parts to make a Prime Machine. You have to set the BIOS to boot on Zip (or LS120). It works perfectly, even if it may be sometimes tricky to make a Zip a system drive (and the only drive of the machine). It's also easy for communicating with PrimeNet : shutdown your "Zip" Windows, take the Zip disquette, put it on your machine with a modem or so, actualize your Prime data and put the Zip disquette back to its machine, boot. This can be done every 3 month or so. Sylvain Perez The guy who's late updating the french Gimps site ... -Message d'origine- De: Kevin Sexton [SMTP:[EMAIL PROTECTED]] Date: mercredi 26 janvier 2000 07:01 A:Mersenne List Objet:Mersenne: small OS setup for mprime Did anyone figure out a simple way to run mprime from a floppy, or small partition? I want to search for primes on a second computer, but the total hard drive space is 650MB, and I have and want to keep dos, and don't have windows of any kind installed. If I figure out how to install it I will add an LS-120 drive. I managed to fit an extremely limited Linux system together with sprime onto a floppy that boots, then unpacks everything into a ramdisk. That was for the extreme of doing a diskless mprime machine, and I never did solve the problem of saving the state without an nfs server, though it might be possible to solve using a samba share for the temp files. - -- Henrik Olsen, Dawn Solutions I/S URL=http://www.iaeste.dk/~henrik/ It wasn't by eliminating the impossible that you got at the truth, how- ever improbable; it was by the much harder process of eliminating the possibilities. You worked away, patiently asking questions and looking hard at things. You walked and talked, and in your heart you just hoped like hell that some bugger's nerve'd crack and he'd give himself up. Commander Vimes on detectoring. Terry Pratchett, Feet of Clay _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers -- Date: Mon, 31 Jan 2000 10:27:36 + From: Gordon Spence [EMAIL PROTECTED] Subject: Mersenne: Re: NT Service Save Files Michael Pedersen wrote: I am using the NT Service version of Prime95. I thought that when I shut down windows the service would be stopped and results saved to disk, but that's not the case. Only if I locate the service and press STOP, the results are saved to disk. I thought that a shutdown would stop all services so the results would be saved, but that doesn't seem to be the case... When you do a system shutdown the results are saved to disk, what *doesn't* happen is an entry being written to results.txt, if you want to see an entry in results.txt then manually stop the service. regards Gordon _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers -- End of Mersenne Digest V1 #685 **
Mersenne: Re: NT Service Save Files
Michael Pedersen wrote: I am using the NT Service version of Prime95. I thought that when I shut down windows the service would be stopped and results saved to disk, but that's not the case. Only if I locate the service and press STOP, the results are saved to disk. I thought that a shutdown would stop all services so the results would be saved, but that doesn't seem to be the case... When you do a system shutdown the results are saved to disk, what *doesn't* happen is an entry being written to results.txt, if you want to see an entry in results.txt then manually stop the service. regards Gordon _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Sorry, but ...
... I don't receive any message from list for a few days ... so that's just a "test". I owe you the equivalent bandwidth of this message. Sylvain Perez _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Chance of P-1 factor
Hi all,
I've been trying to figure out what the chance of finding a P-1 factor
is, given a certain amount of trial factoring and a P-1 bound.
I started with:
The chance of Mp having a factor in [2^n, 2^(n+1)] is 1/n.
The chance of a number N being B-smooth is
(log(B)/log(N))^(log(N)/log(B)) .
Since we know factors of Mp are f = 2kp+1, the difficulty of the problem
of finding f is reduced to factoring k.
So the chance that a factor of Mp can be found by P-1 with bound B is
(log(B)/log(f/2p)) ^ (log(f/2p)/log(B)) .
I get the probabilities of finding any factor by running over factor
sizes in bits (powers of two) and add up the product of the prob of Mp
having a factor of n bits and the prob of P-1 finding such a factor. (In
fact, I make two lists and get the dot product)
Mathematica:
Pfactor[L_] := Table[If[nL,1/n,0],{n,200}];
// The probabilities of Mp having a factor of n bits, after trial
factoring up to 2^L
Psmooth[B_,p_] := Table[
If [(n-Log[2,2p])Log[2,B],
1,
(Log[2,B]/(n-Log[2,2p]))^((n-Log[2,2p])/Log[2,B])],
{n,200}];
//The chance of P-1 finding a factor of size n of Mp with stage 1 bound
B
N[Psmooth[100,3300].Pfactor[68]]
0.026342
This would mean that we'd find factors of only 2.6% of the 10 million
exponents, even with a bound of 1M ! Thats pretty disappointing.
Now, is the above about correct ?? I'm pretty unsure about my math, so..
at least N[Psmooth[400,30].Pfactor[53]] ~= 10% which is close to
my empirical data, if a little low ( I get about 11-12% success rate
with B1=100k, B2=4M).
How much error does my quantizing factor sizes to powers of 2 introduce?
And what is the probability of a number being B1-smooth with a single
factor f B1fB2 (for P-1 with stage 2) ?
And it just occurred to me: if we know that Mp is composite (because we
did an LL test), after trial factoring the chance for larger factors
must increase, because the interval in which the factor must lie is
narrowed down. How can I take that into account?
Any help would be much appreciated!
Ciao,
Alex.
_
Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Chance of P-1 factor
Hi, At 02:21 PM 1/31/00 +, Alexander Kruppa wrote: I started with: The chance of a number N being B-smooth is (log(B)/log(N))^(log(N)/log(B)) . I don't think this is correct. Look up Dickman's function in Knuth vol 2 pages 382 and 383. You can also look at a July 10, 1996 post to this mailing list from Peter-Lawrence Montgomery. I've been grappling with this same problem in prime95 version 20. I'll let you independently implement it and see if out results agree! Regards, George _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Version 20 memory questions
Hi all, I'm working on prime95 version 20. The important new feature is a P-1 factoring step prior to a Lucas-Lehmer test. The P-1 factoring step has a 3-5% chance of finding a factor at a cost of 2-4% of an LL test. The net effect is we speed up GIMPS' throughput by a percent or two (more if you factor in the fact that a double-check is avoided too). Stage 2 of P-1 factoring requires more memory than an LL test. The more memory you give the program the faster stage 2 executes. For example, an exponent around 10 million requires about 4MB of data. P-1 stage 2 would like to have 48MB, but can get by with as little as 24MB. The good news is that the LL test takes a month, P-1 factoring takes a day, and the memory hungry stage 2 takes only half a day. GIMPS has always had a good reputation for not interfering with your normal work. To preserve GIMPS' reputation, I'm thinking of implementing the following. In the Options/CPU dialog, prime95 will let you select the maximum amount of memory the program can use and the hours of the day it can use it. The default would be 80% of RAM (divided by the number of CPUs) during nighttime hours only. Finally, the questions: Would we be better off disabling P-1 factoring unless the user explicitly activates it (knowing that most users won't read enough to turn it on)? Are there better solutions? It would be nice if prime95 could detect that memory thrashing was happening and pause itself until more memory was available. Can Windows programs do this? Are the defaults too aggressive (especially the 80% of RAM)? You can send your comments and suggestions to me privately or to the entire mailing list. Having fun, George _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Version 20 memory questions
At 11:38 AM 1/31/00 -0500, George Woltman wrote: Would we be better off disabling P-1 factoring unless the user explicitly activates it (knowing that most users won't read enough to turn it on)? That sounds like a good idea to me. Giving up 24-48MB would interfere with some people's work, and you don't want to do that. Prime95 needs to be transparent. It probably should be in the advanced menu, and allow you to set the hours and days. ++ | Jud McCranie | || | 137*2^197783+1 is prime! (59,541 digits, 11/11/99)| | 137*2^224879+1 is prime! (67,687 digits, 1/00)| ++ _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Version 20 memory questions
This is one vote for memory conumsion by default stays at 4ish MB, and only if you change it on the advanced menu will it use more. I know too many people who never read the docs and will have no idea why their computer "got slow" when they put on ver. 20 and will just want it taken off. Louis Towles _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Version 20 memory questions
George Here is another vote for P-1 to default to off unless it is explicitly enabled using the Advanced Menu like ECM. Regards Alan Powell [EMAIL PROTECTED] _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Version 20 memory questions
GIMPS has always had a good reputation for not interfering with your normal work. To preserve GIMPS' reputation, I'm thinking of implementing the following. In the Options/CPU dialog, prime95 will let you select the maximum amount of memory the program can use and the hours of the day it can use it. The default would be 80% of RAM (divided by the number of CPUs) during nighttime hours only. Um, 80%? I have 384MB in this box. 80% of 384MB is like 300MB! I hope that would be limited to the min/max amount of memory you need to do useful work? Since I have 384MB, I would have no problem dedicating 48MB to this 24/7. Finally, the questions: Would we be better off disabling P-1 factoring unless the user explicitly activates it (knowing that most users won't read enough to turn it on)? Are there better solutions? It would be nice if prime95 could detect that memory thrashing was happening and pause itself until more memory was available. Can Windows programs do this? Yes, you can get various statistics out of the system re: paging etc, but I believe the exact method is different on win9X and NT/w2k. I think someone elses suggestion might be better, detect when the system slows down and back off for 5 minutes or something. I would think 20% or something would be a better default. if someone has 128MB, thats 24MB. If they have 256MB, thats 48MB. if they have less than 128MB, they really can't afford to run this at all unless its on a dedicated basis. -jrp _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
