Mersenne Digest Tuesday, February 6 2001 Volume 01 : Number 813 ---------------------------------------------------------------------- Date: Sat, 3 Feb 2001 23:16:56 -0800 From: "Stephan T. Lavavej" <[EMAIL PROTECTED]> Subject: Mersenne: Re: Mersenne Digest V1 #812 >What about some of the new gaming platforms. I think some have computing >capabilities equivalent to P133s and they have modem hookups. However, I'm > not sure how feasible/worthwhile it would be to write progamrs to do this. Better yet, the Xbox. It will actually have a PIII-733 inside it, AND a hard drive, and a built-in broadband connection. All that would be required is the ability to run arbitrary code from the hard drive, and poof, you have something like a million potential boxes on which to run Prime95. Stephan T. Lavavej http://quote.cjb.net _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 4 Feb 2001 01:50:18 -0600 From: "Steve" <[EMAIL PROTECTED]> Subject: Re: Mersenne: idea for a new prime95 version >"Alexander Kruppa" wrote: > >The screen-saver idea is important for another reason. >I asked several coworkers and secretaries to let Prime95 (NTprime, >actually) run on their PCs and they agreed, but they were less than >happy when I asked them to change the pretty 3-d screen savers for >something that lets NTprime have more cpu power. With the selection >Microsoft offers right now, that means "Blank Screen" or "Marquee" - >neither is extremely exciting to watch. Before long, most of them went >back to the old screen savers and NTprime slowed down to a halt. "...slowed down to a halt" is no exaggeration. I've seen screensavers slow it down to more than 7 seconds per iteration at 800+ MHz. I have it running on some PCs where the user has the screensaver set to start after 5 minutes then sets the power management so the monitor turns off after 10 or 15 minutes... and what really bothers me is that the screensaver continues to run even with the monitor off. (Is there some way to prevent that which I don't know about?) One idiot even had her settings such that the screensaver didn't start until _after_ the monitor went off. There are so many screensavers available now that one can be found to match any personality, and I have found it impossible to get people to let go of one they really like. So I don't believe Brian's idea will do very much good; but then every little bit helps. Steve Harris [EMAIL PROTECTED] _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 04 Feb 2001 00:16:03 -0800 From: Luke Welsh <[EMAIL PROTECTED]> Subject: Re: Mersenne: idea for a new prime95 version At 01:50 AM 2/4/01 -0600, Steve wrote: >There are so many screensavers available now that one can be found to match >any personality, Why not identify a couple of existing screensavers that could be "compatible" with Prime95 and then approach the author(s)..... ask them to make a verion that includes George's stuff? - --Luke _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 4 Feb 2001 14:36:05 -0000 From: "Brian J. Beesley" <[EMAIL PROTECTED]> Subject: Re: Mersenne: idea for a new prime95 version, QA, primenet etc On 3 Feb 2001, at 17:03, Jeff Woods wrote: > > >With increasing exponent size (and therefore run time), I'd like to > > >see PrimeNet evolve to track intermediate residues & also to be able > > >to coordinate parallel LL testing & double-checking, so that runs > > >which are going wrong can be stopped for investigation without having > > >to be run through to the end. > > I think this is an EXCELLENT idea, but remember that the "s" values (i.e. > the intermediate residue/modulus) for such numbers is quite simply > enormous. One couldn't (and shouldn't) check the entire intermediate > value, but merely the last "x" bits, where "x" is enough to be reasonably > certain that a match isn't random chance -- say, the final 1024 bits. 64 bits is enough to be pretty confident! We need a recovery procedure anyway, to cope with any systematic bugs which may exist. > > PrimeNet would thus also have to carefully assign the exponents to similar > machines with similar runtimes and performance, as it would do little good > to assign the primary test to an Athlon-800 and the "real-time" > double-check to a much slower machine, as the Athlon would quickly outpace > the second check. > > If a discrepancy was found in a real-time double-check, a ternary run on a > different machine could determine which (if either) of the two intermediate > residuals was correct, and the tests could proceed from there, with both > original machines assuming the same correct residue. > My reply to Ken Kriesel's message on this topic shows how the need for paired systems to be evenly matched could be avoided - though it is certainly preferable that gross mismatches are avoided. However, there shouldn't be much problem providing reasonable matches, since the PrimeNet server knows each participating system's CPU type & clock speed. > Also, if this did evolve, I'd suggest that the "double-checker" be given > equal credit with the primary machine, for purposes of credit in history > books as discoverers, and/or EFF monies. This question obviously needs to be addressed, if only to keep lawyers out of our hair. I agree with Jeff on this one. > > Note that there's a point of futility, at which a "tie-breaker" ought to > merely be a triple-check, run to conclusion. Let's say on a 14-month co-op > effort, 13.6 months into it a discrepancy was found. Both machines ought > to finish, and just have it triple-checked, rather than suspending both, > awaiting a tiebreaker. While I'm sure someone could solve for the optimum > cutoff point where tiebreakers are not useful, my guess would be that it is > around 85% of the way to completion. With the suggestions in my reply to Ken, having "late" checkpoints doesn't do much to slow down completion - the leading system proceeds unless or until the trailing system finds a discrepancy. However, I certainly agree that there's not much point in having a checkpoint at iteration 14 million if you're testing e.g. exponent 14000003. I'd suggest "missing out" the last checkpoint if the number of iterations remaining at that point is less than half the iterations between checkpoints. Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 4 Feb 2001 14:36:05 -0000 From: "Brian J. Beesley" <[EMAIL PROTECTED]> Subject: Re: Mersenne: idea for a new prime95 version On 4 Feb 2001, at 1:50, Steve wrote: > >"Alexander Kruppa" wrote: > > > >The screen-saver idea is important for another reason. > >I asked several coworkers and secretaries to let Prime95 (NTprime, > >actually) run on their PCs and they agreed, but they were less than > >happy when I asked them to change the pretty 3-d screen savers for > >something that lets NTprime have more cpu power. With the selection > >Microsoft offers right now, that means "Blank Screen" or "Marquee" - > >neither is extremely exciting to watch. Before long, most of them went > >back to the old screen savers and NTprime slowed down to a halt. > > > "...slowed down to a halt" is no exaggeration. I've seen screensavers slow > it down to more than 7 seconds per iteration at 800+ MHz. I have it running > on some PCs where the user has the screensaver set to start after 5 minutes > then sets the power management so the monitor turns off after 10 or 15 > minutes... and what really bothers me is that the screensaver continues to > run even with the monitor off. (Is there some way to prevent that which I > don't know about?) Not that I'm aware of, either. You're supposed to use ACPI to make the processor sleep rather than worry about details such as whether the screensaver is still running with no visible display. > One idiot even had her settings such that the screensaver > didn't start until _after_ the monitor went off. No accounting for stupidity! I wonder if you could get away with tricking users like this into staring at the "blank screen" saver for hours on end by fooling them that, very occasionally, something "interesting" happens? ;-> > > There are so many screensavers available now that one can be found to match > any personality, and I have found it impossible to get people to let go of > one they really like. So I don't believe Brian's idea will do very much > good; but then every little bit helps. Could I respectfully point out that the windoze screensavers run at priority 4. If you raise Prime95/NTPrime's priority to 4, you will split CPU time more or less evenly between the screensaver and the Mersenne client. In fact there should be a bit more going our way than the screensaver does; the screensaver does voluntarily relinquish the CPU occasionally - otherwise a client running at priority 1 would get nothing. On the principle that half a system is better than nothing, this trick is probably worth publicising, if it will let users keep their favourite screensaver running. I'd warn strongly against raising the priority of Prime95/NTPrime any higher than 4, as there could be serious consequences to the performance of foreground tasks. BTW, and getting way off topic, on windoze I use a freeware gadget called Sleeper which I downloaded from the net ages ago. Still works on Win2K though. This has "hot spots" in two corners of the screen (configurable in size and which two corners are used); if you park the mouse pointer in one of the "hot spots", the screensaver activates "immediately" (actually there is a 2 sec delay) whilst parking the mouse pointer in the other "hot spot" prevents the screensaver from ever activating. If the mouse pointer is elsewhere, the screensaver activation is normal (as if Sleeper were not present). I use this (in conjunction with the screensaver password feature, and the standard "blank" screen saver) as a security tool, to lock access to my system through the console when I'm temporarily absent e.g. gone for a leg stretch. Obviously you need to set the BIOS boot & setup passwords as well, to prevent people from breaking in by simply resetting the system. And, no, it isn't perfect, but then no security system is. The "never activate" feature is also useful, as it prevents screensaver activation from interfering with tasks like scandisk and defrag which don't take kindly to anything happening which causes the volume being processed to be accessed. Sleeper is tiny and has no detectable processing time overhead. Obviously it does need to steal a few cycles, but it really isn't significant, even on a slow system. Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 4 Feb 2001 14:36:05 -0000 From: "Brian J. Beesley" <[EMAIL PROTECTED]> Subject: Re: Mersenne: Re: Mersenne Digest V1 #812 On 3 Feb 2001, at 23:16, Stephan T. Lavavej wrote: > >What about some of the new gaming platforms. I think some have computing > >capabilities equivalent to P133s and they have modem hookups. However, I'm > > not sure how feasible/worthwhile it would be to write progamrs to do this. P133 isn't much by modern standards. > > Better yet, the Xbox. It will actually have a PIII-733 inside it, AND a > hard drive, and a built-in broadband connection. All that would be required > is the ability to run arbitrary code from the hard drive, and poof, you have > something like a million potential boxes on which to run Prime95. Assuming, of course, that PIII-733s are still available when the Xbox goes into mass production. Intel's production strategies might force use of a more powerful processor :) I guess it will be running something that is recognisably Windows "under the hood", as well. In which case, the programming overhead might be _very_ small. I also guess that there _will_ be some means of running third-party code ... people are going to want to do things that Microsoft haven't thought of ... the free market system usually manages to rectify these sorts of deficiencies! Furthermore, I'd guess that Bill Gates would be rather distressed to hear your estimate of only one million sales. He probably hopes unit sales will run into eight figures. Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 04 Feb 2001 10:57:12 -0500 From: Marcel van de Vusse <[EMAIL PROTECTED]> Subject: Re: Mersenne: idea for a new prime95 version Steve wrote: > "...slowed down to a halt" is no exaggeration. I've seen screensavers slow > it down to more than 7 seconds per iteration at 800+ MHz. I have it running > on some PCs where the user has the screensaver set to start after 5 minutes > then sets the power management so the monitor turns off after 10 or 15 > minutes... and what really bothers me is that the screensaver continues to > run even with the monitor off. (Is there some way to prevent that which I > don't know about?) One idiot even had her settings such that the screensaver I have to agree here. I installed Prime95 on my parent's computer, and took it off again after I found out the screen saver keeps going after windows turns the monitor off (3D flowerbox or something like that). I guess I overestimated microsoft's intelligence when I actually expected the screen saver to quit after the monitor was blanked (end eventually turned off). Is there any way somebody could modyfy this behavious? Marcel - -- "'Chapter Fifteen, Elementary Necromancy'", she read out loud. "'Lesson One: Correct Use of Shovel...'" Terry Pratchett, Jingo _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 04 Feb 2001 17:58:24 +0100 From: Martijn <[EMAIL PROTECTED]> Subject: Mersenne: Statistics Hi I think the overall statistics updated ~ daily makes seti and distributed.net "sexier" than primenet. When hooking up that brand new 1.2 GHz machine, you have the first results in 1-2 days, (Score wise) I think it might help to award primenet points at every progress report. The score can be sorted on total score for finished work + a Work In Progress (WIP)score (1 partial score / computer ID) That way people will get faster statistic results which actually is important to a lot of people. When a computer reports the final result the WIP can be reset to 0 and the finished work score can be increase with the points for the finished exponent (as now). The comptational overhead can be kept low if only one top list is made a day (this is the same frequency as distributed.net and probably also the same as the seti statistics charts.) Kind Regards, Martijn _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 04 Feb 2001 18:07:31 +0100 From: Alexander Kruppa <[EMAIL PROTECTED]> Subject: Re: Mersenne: idea for a new prime95 version "Brian J. Beesley" wrote: > > On 4 Feb 2001, at 0:27, Alexander Kruppa wrote: > > Well, you could bump NTprime's priority to 4; that would let NTprime > steal CPU cycles off the screensaver, without being too obvious to > the user :) Don't go any higher, as you would risk seriously > impacting the performance of foreground tasks. One big point you can use to convince coworkers/managers etc is that Prime95 only uses cpu time that no other process wants. Most everyone I asked wanted explicit confirmation that Prime95 does not take cpu time while other processes are running. I can just see them frowning at me when I say that Prime95 will now steal only such a little amount of cpu time.. No, I think Prime95 really should run at idle priority. > > With the selection > > Microsoft offers right now, that means "Blank Screen" or "Marquee" - > > neither is extremely exciting to watch. Before long, most of them went > > back to the old screen savers and NTprime slowed down to a halt. > > Does that mean that the primary purpose of the computers used by your > coworkers is to provide a colourful distraction? Putting a picture on a wall in an office is not the primary purpose of an office either, yet most everyone I know does it. Everyone can set up his workplace the way he wants it. I can't go and tell them what to do with their computers, I was happy enough when they agreed to let me install a strange piece of software. If they like colorful displays then why shouldn't they have them? The solution would be to write a screen saver that is pleasing to look at (and not just for tech dweebs) and yet leaves enough cpu time for an idle-priority background process. > I suppose you could try fibbing that something interesting happens > occasionally in the blank screen (like the teapot in the 3D pipes > saver), and see how long you can make them stare at it ;-> > > Regards > Brian Beesley How about a cute kitten that sleeps for hours, wakes up, stretches, walks to another corner of the screen and sleeps some more? 99% static graphics, has the "oh sweet!!" bonus and people will try to leave the computer alone as not to disturb the kitten while Prime95 happily crunshes away :) Ciao, Alex. _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 05 Feb 2001 06:32:52 +1300 From: "Halliday, Ian" <[EMAIL PROTECTED]> Subject: [Fwd: Re: Mersenne: Distributed Computing Mandatory For Juno's Free Users] >From Nathan, for the list From: Nathan Russell <[EMAIL PROTECTED]> References: <[EMAIL PROTECTED]> Halliday, Ian wrote: > http://au.dailynews.yahoo.com/headlines/20010203/nbtech/981156900-2685255736.html > describes new conditions for free juno users - once again SETI is cited > as a "successful" example of distributed computing. IIRC, we have had > four successes, they haven't had any... Yes, we have. If GIMPS succeeds yet again, the finder of the prime will get money, and fame within the mathematical community. Ditto if a user of the distributed.net project finds a RC5 key (except less money and more transitory fame). It could be argued that someone who finds /them/ with SETI and is announced as a co-discoverer will not be wanting for fame or money for the rest of his/her life. Additionally, SETI is as likely to make a discovery now as it ever was (read: not very). d.net and GIMPS are both attempting tasks which are orders of magnitude less likely to succeed than those they have completed in the past. As another point, I know many who are in SETI solely for the nice graphical display. I don't know whether GIMPS, given the abstract nature of the work we do, could ever really develop such a display. > > How will the new conditions described in their terms affect us (or any > other voluntary distributed project for that matter) ? I sincerely doubt that many Juno users will stick with that service if Juno ever attempts to fully enforce the terms: "[users permit Juno to] upload such results to Juno's central computers during a subsequent connection, whether initiated by you in the course of using the Service or by the Computational Software." (snip) "Juno may require you to leave your computer turned on at all times, and may replace the 'screen saver' software that runs on your computer while the computer is turned on but you are not using it. " Does that mean that Juno will become angry at subscribers who take their machines down for maintence, or do a reboot mandated by the operating system? My ex-girlfriend from high school and her family use Juno as their free email provider. I sincerely doubt that, if Juno began enforcing these sorts of terms, they would switch to e.g. NetZero or another adware internet provider, and begin using web-based email. The privacy concerns alone of Juno running software quasi-voluntary on customer systems are chilling. I just checked Slashdot, but they've had something up since yesterday: http://slashdot.org/article.pl?sid=01/02/01/2127239&mode=nested > > > On a different matter, what happened to Lennart's offer of champagne to > the person who guessed a milestone date correctly? Have we reached that > milestone yet? If so, who won? > > Regards, > > Ian Nathan Russell _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 04 Feb 2001 15:10:22 -0500 From: "Joshua Zelinsky" <[EMAIL PROTECTED]> Subject: Mersenne: Re: idea for a new prime95 version >Could I respectfully point out that the windoze screensavers run at >priority 4. If you raise Prime95/NTPrime's priority to 4, you will >split CPU time more or less evenly between the screensaver and the >Mersenne client. In fact there should be a bit more going our way >than the screensaver does; the screensaver does voluntarily >relinquish the CPU occasionally - otherwise a client running at >priority 1 would get nothing. It would be really useful if this was in the readme file _ FAQ list. Regards, Joshua Zelinsky _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 4 Feb 2001 21:22:22 +0100 From: Lars Lindley <[EMAIL PROTECTED]> Subject: Re: Mersenne: idea for a new prime95 version, QA, primenet etc > >> Nothing built by human hands is perfect, so, sure, the program could > >> be improved! Personally I'd like to see an optimization for Athlon; > >> at the expense of having to load different versions for different > >> processor types, I'd like to see seperate "streamlined" versions of > >> the code optimized for different processor types rather than one > >> monolithic program with everything embedded in it; Optimizations for Athlon would be very welcome :) Using a modularized version of the program (sort of like dll's) would keep the simlicity in using the program AND keep it resource-efficient. The added download time shouldn't be a problem since it is a one-time download and for example SETI@Home requires daily downloads on a fast machine. (That project isn't going all to bad :)) just my two cents... /Lars _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Sun, 4 Feb 2001 15:38:37 -0600 From: "Steve" <[EMAIL PROTECTED]> Subject: Re: Mersenne: Re: screensavers >Could I respectfully point out that the windoze screensavers run at >priority 4. If you raise Prime95/NTPrime's priority to 4, you will >split CPU time more or less evenly between the screensaver and the >Mersenne client. In fact there should be a bit more going our way >than the screensaver does; the screensaver does voluntarily >relinquish the CPU occasionally - otherwise a client running at >priority 1 would get nothing. A while back I set the priority for Prime95 to 5 at night and left it at 1 during the day on several PCs. In some cases in helped tremendously but in other cases it had no effect whatsoever. I don't remember if that correlated with machine type, OS or screensaver type; it was quite some time ago. I may revisit that and look for a pattern. I do remember one in particular, the "win95" screensaver running on a pentium pro with Win95 OS brought Prime95 almost to a dead stop, but changing the priorities at night slowed the screensaver so much you could barely see it move while Prime95 ran almost at optimum speed. I remember that one because it was the most successful implementation of the resetting of priorities. Others ranged from some effect to no effect. I believe the least successful were some screensavers which did not come with windows but were downloaded from elsewhere; but I am also sure there were some that came with the OS that were just as bad. Steve Harris _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 5 Feb 2001 00:09:46 +0000 (GMT) From: Russel Brooks <[EMAIL PROTECTED]> Subject: Re: Mersenne: idea for a new prime95 version Idea for a screensaver for Prime95, let the user specify a directory of picture files and Prime would pick one to display every few minutes. Decoding a JPG or GIF would suck up some cycles but between picture updates Prime would get them all. Cheers... Russ _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 5 Feb 2001 22:45:23 +0000 (GMT) From: Russel Brooks <[EMAIL PROTECTED]> Subject: Mersenne: Re: idea for a new prime95 version Joshua Zelinsky wrote: > >directory of picture files and Prime would pick one to display > > Unfortunately, the people who care enough about their screensavers to make > them Prime95 non-friendly are probably not going to be willing to settle for > a few still shots. The cat idea still sounds really good. Maybe, but with the increasing popularity of digital camers it would allow people to build a 'personal' screen saver with their own pictures. Cheers... Russ _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Tue, 6 Feb 2001 01:55:32 +0100 From: "Robert van der Peijl" <[EMAIL PROTECTED]> Subject: Mersenne: Reliability of prime95 vs. PRP Hi all, some of us may have an old Pentium-I or similar system standing around. Those systems could be set to good use in our mersenne prime search. They could get factoring or double-checking assignments. But what if you just want to do first-time tests? Newcomers may not want to wait many months to get just one result. Maybe at first they just want to discover a prime that makes it to the top 100. So they could go for a prime of, say, formula k*2^n+1. They could run NewPGen to screen a range of numbers of that formula for small factors. Then run PRP to test each number in turn for probable primality. If it finds a probable prime, the Proth program could do the final and definitive test on that number. It all works really well. Once they would discover such a big prime -- which usually doesn't take very long to do -- they may have developped a taste for it, and decide to join in and help us in our search for a new #1. But what about the reliability of the result of each test in PRP? Prime95 reports errors such as 'ILLEGAL SUMOUT' and roundoff errors if they occurr during the Lucas-Lehmer test. I'm wondering if PRP is about equally good at detecting errors during a calculation? Maybe it would be useful to show a 64-bit residue after completion of the probable prime test? Re-running the same test would then tell you if the number is indeed composite. For now, it looks to me like GIMPS is the most reliable way of looking for primes. Does anyone on the list have a view on this? Robert van der Peijl Eindhoven, The Netherlands _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 05 Feb 2001 22:06:07 -0500 From: George Woltman <[EMAIL PROTECTED]> Subject: Re: Mersenne: Reliability of prime95 vs. PRP Hi, At 01:55 AM 2/6/2001 +0100, Robert van der Peijl wrote: >So they could go for a prime of, say, formula k*2^n+1. >They could run NewPGen to screen a range of numbers of that formula for >small factors. >Then run PRP to test each number in turn for probable primality. >If it finds a probable prime, the Proth program could do the final and >definitive test on that number. It all works really well. For those unfamiliar with the Proth prime search, visit http://www.utm.edu/research/primes/programs/gallot/ for more details. NewPGen sieves out k*2^n+1 that have small factors, Proth tests the remaining candidates for primality. About a year ago, I wrote PRP, based on prime95's multiplication routines, to run as an intermediate step to do a probable prime test. I publicized the program on the primes mailing list: http://groups.yahoo.com/group/primenumbers Also, scan Chris Caldwell's excellent site for the OpenPFGW program (grossly misnamed with my initials when Chris Nash did all the work!) This tests the primality of other special forms of numbers again using prime95's multiplication routines. Using either of the above programs, it is relatively easy to find a prime that cracks the top 5000 list at http://www.utm.edu/research/primes/largest.html >But what about the reliability of the result of each test in PRP? >I'm wondering if PRP is about equally good at detecting errors during a >calculation? PRP uses the same sumout checks that prime95 does. >Maybe it would be useful to show a 64-bit residue after completion of the >probable prime test? True, but no one has volunteered to keep a central list of residues, much less organize a rigorous search of Proth candidates. >For now, it looks to me like GIMPS is the most reliable way of looking for >primes. Does anyone on the list have a view on this? Both are quite reliable methods for finding primes. One is good at finding good sized primes, the other good at finding record primes. BTW, the Proth program and OpenPFGW program could be used to find world-record primes. They are less than half as efficient as prime95 - but you get to test numbers that are much smaller than the M12000000 currently being assigned by Primenet. Regards, George _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 5 Feb 2001 22:38:18 -0600 From: "Steve" <[EMAIL PROTECTED]> Subject: Re: Mersenne: Re: idea for a new prime95 version Excellent idea, Russ. I was discussing with Like Welsh the problem of people attached to their killer screensavers, and as he pointed out: "But maybe they'd watch pic of their kids/dog/vacation instead? The *particular* screensaver I was thinking of was the Photo Slide Show variety. Slap an image on the screen, wait 15 seconds, fade out, display another. Lots of free CPU time between pics." Certainly it won't work for everybody, but I'm sure there would be a lot of takers. Now, anybody know how to write such a thing? Could be released with the prime95/NT software or as a seperate item to be downloaded from the same site. Steve Harris - -----Original Message----- From: Russel Brooks <[EMAIL PROTECTED]> To: [EMAIL PROTECTED] <[EMAIL PROTECTED]> Date: Monday, February 05, 2001 5:19 PM Subject: Mersenne: Re: idea for a new prime95 version >Joshua Zelinsky wrote: >> >directory of picture files and Prime would pick one to display >> >> Unfortunately, the people who care enough about their screensavers to make >> them Prime95 non-friendly are probably not going to be willing to settle for >> a few still shots. The cat idea still sounds really good. > >Maybe, but with the increasing popularity of digital camers it >would allow people to build a 'personal' screen saver with their >own pictures. > >Cheers... Russ > >_________________________________________________________________________ >Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm >Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Tue, 6 Feb 2001 00:56:58 -0600 From: "Jeramy Ross" <[EMAIL PROTECTED]> Subject: Mersenne: Re: idea for a new prime95 version From: "Steve" <[EMAIL PROTECTED]> *snip* Could be released with the prime95/NT software or as a seperate item to be downloaded from the same site. Steve Harris *snip* I'd rather the seperate item bit. That would allow those who wanted such a beast to install it at their will, and those of us whom dislike the idea of having a screensaver taking *any* cycles away from prime95 can stick with the good ol' interface we have grown to love. ;-) Jeramy Ross _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Tue, 6 Feb 2001 19:58:49 -0000 From: "Brian J. Beesley" <[EMAIL PROTECTED]> Subject: Re: Mersenne: Reliability of prime95 vs. PRP On 5 Feb 2001, at 22:06, George Woltman wrote: > >Maybe it would be useful to show a 64-bit residue after completion of the > >probable prime test? > > True, but no one has volunteered to keep a central list of residues, much > less organize a rigorous search of Proth candidates. Is this really neccessary? I'd be more interested in what happens to those candidates which pass PRP and go on to Proth, or PrimeGen. If Proth finds "not prime" it doesn't tell you anything else. There is a chance that something glitched. Presumably also the residue will depend on which base you use for the Proth test, I'm not sure the program always makes the same choice. Please excuse my ignorance. However I certainly agree that the search needs to be organized better before anyone starts worrying about possibly missing ~1% of the primes in a "searched" range. I messed around with Proth a couple of years ago, registered some ranges (the mechanism doesn't seem to have changed since) and found 4 primes over 20,000 digits in a couple of P100 CPU months - these were just about "top 500" at the time - of which 2 turned out to be rediscoveries from someone else working on the same ranges without bothering to register them. Not very encouraging :( When Proth does find a prime, it verifies it by a second test using the same program on the same system but using a different base. This doesn't "feel" as good as GIMPS/PrimeNet's independent double- checking mechanism. Incidentally, am I missing something? The Fermat test for pseudoprimality (which is equivalent to a Proth test for true primality, given a suitable candidate number and a suitable choice of base) takes as long to run as a LL test on a number of the same size. So, what test is PRP running? Obviously there's no point in running Fermat's test with base 2 for Mersenne numbers, but I find it somewhat less obvious that Fermat's test with base 2 would eliminate a useful proportion of Proth candidates. If PRP is doing something else, and runs significantly faster than Fermat's test, is there any point in using it to pre-filter Mersenne candidates??? > > >For now, it looks to me like GIMPS is the most reliable way of looking for > >primes. Does anyone on the list have a view on this? > > Both are quite reliable methods for finding primes. One is good at finding > good sized primes, the other good at finding record primes. BTW, the > Proth program and OpenPFGW program could be used to find world-record > primes. They are less than half as efficient as prime95 - but you get to > test numbers that are much smaller than the M12000000 currently being > assigned by Primenet. Before June 1999 there was some discussion about using Proth to find a million-digit prime for the EFF prize. Things may have changed since, but I seem to remember that a new version of Proth was rushed through to give it this capability, and even then the code used was becoming distinctly marginal when testing numbers of that size. The (semi-)organized use of Proth has concentrated on smaller numbers; the biggest would be candidate Cullen prime numbers (p.2^p+1) with p around 1 million, i.e. the order of 300,000 digits. Robert's suggestion of using old, slow Pentium systems would make very little sense if you were wanting to use Proth or OpenPFGW to look for prime numbers around 2^7,000,000. The run times would be just as long as LL test assignments using Prime95. Regards Brian Beesley _________________________________________________________________________ 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 #813 ******************************
