Mersenne: Re: Factoring benefit/cost ratio

2001-11-30 Thread Steve Harris 

Actually, Richard's statement that a 'Factored' status is better for GIMPS
than a 'Two LL' status is not quite true. It's better for the mathematical
community as a whole, but not for GIMPS. GIMPS is looking for primes, not
factors, and without skipping over any. This means all candidates must be
tested and the non-primes eliminated, and it doesn't matter whether they are
eliminated by 'factored' or by 'two matching nonzero LL residues'. It
matters  to those who are attempting to fully factor Mersenne numbers, but
that's a different project altogether, and one that is decades (at least)
behind GIMPS. The only reason we do any factoring at all is to reduce the
time spent on LL testing.

Besides, if you do manage to find a 75-digit factor of a 2-million-digit
Mersenne number, that still leaves a 125-digit remainder. Really not
much help :-)

Regards,
Steve Harris

-Original Message-
From: Daran [EMAIL PROTECTED]
To: [EMAIL PROTECTED] [EMAIL PROTECTED]
Date: Friday, November 30, 2001 2:00 AM
Subject: Re: Factoring benefit/cost ratio (was: Mersenne: Fw: The Mersenne
Newsletter, issue #18)


- Original Message -
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Saturday, November 24, 2001 6:49 PM
Subject: Factoring benefit/cost ratio (was: Mersenne: Fw: The Mersenne
Newsletter, issue #18)

 But ones factoring benefit calculation might [should would be in
 line with the popular theme of prescribing what's best for other
 GIMPS participants :)] include not only the time savings of
 eliminating the need for one or two L-L tests, but also the extra
 benefit of finding a specific factor.

I can see no way of objectively quantifying this benefit.

 In the GIMPS Search Status table at www.mersenne.org/status.htm the
 march of progress is from Status Unknown to Composite - One LL to
 Composite - Two LL to ... Composite - Factored.

More desireable - whether or not recorded on that page - would be
Composite - Least (or greatest) factor known.  Most desireable (other
than
Prime) would be Composite - Completely factored'.

 This reflects the view (with which I agree) that it is more valuable
 to know a specific factor of a Mnumber than to know that a Mnumber is
 composite but not to know any specific factor of that Mnumber.

 So a Factored status is better for GIMPS than a Two LL status, but
 calculations of factoring benefit that consider only the savings of
 L-L test elimination are neglecting the difference between those two
 statuses.  If one consciously wants to neglect that difference ...
 well, okay ... but I prefer to see that explicitly acknowledged.

It seems to be implicitely acknowledged in the way the trial factoring
depths are determined.  If one places a non-zero value on a known factor,
then the utility of extra factoring work on untested, once tested, and
verified composites would be increased.  It would have to be set very high
indeed to make it worth while returning to verified composite Mersennes.

 Richard Woods

Daran G.


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Mersenne: Re: need access to an SGI

2001-11-30 Thread EWMAYER 

Thomas Ritschel has been kind enough to build binaries of
Mlucas 2.7c for me. Now I need some guinea pigs, er, I 
mean, beta testers. Thomas has built both 32-bit and 
64-bit executables and verified that they run and done 
timings on the R1 and R12000 systems he has access 
to. These are all fairly recent CPUs (i.e. they can 
handle 64-bit binaries) with large L2 caches. Now I need  to try the code out on some 
older and smaller-cache 
systems. If you have access to an SGI which is either 
pre-R1 or an R1 with an L2 cache of 1MB or 
smaller and you are willing to do some tests for me, the 
tarball is at

ftp://hogranch.com/pub/mayer/bin/SGI/Mlucas_SGI.tar.gz

This contains a 32-bit and a 64-bit executable, and
several .cfg files with the optimal radix combinations
Thomas found on his systems. In order to run the same
suite of timing tests so you can create the .cfg file
optimal for your system, you'll need to also grab the
source tarball:

ftp://hogranch.com/pub/mayer/Mlucas_2.7c.tar.gz

This tarball contains a timings.txt file, which has
a complete set of entry fileds for doing benchmarks. If 
your system is pre-R1, you only need do runs up to an 
FFT length of 1024K, unless you're curious and willing to 
burn the CPU time that will be needed to do the larger
runlengths.

I'll need answers to the following questions:

1) What type of system did you do benchmarks on?
   ('hinv' will give CPU and cache info; 'uname -a'
   should tell you which OS.)

2) Did both the 32-bit and 64-bit binaries run on your 
   system? If yes, which is faster?

3) For the faster of the 2 binaries, a .cfg file with the
   optimal radix set index for each FFT length, and the
   table of per-iteration timings for all radix
   sets you tried for each FFT length. Please send these
   data in simple plaintext mode.

Thanks in advance,
-Ernst

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Mersenne: I have a RISC/6000 with AIX 3.1 installed

2001-11-30 Thread Torben Schlntz 

This might run anything;  but I'm probably to stupid to manage to set up
anything on it. :-/
Can anyone use this machine as is for any purpose related offcourse to
primechruncing?
 
br tsc
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