Re: Mersenne: Version 18.1
On Thu, 1 Apr 1999, George Woltman wrote: As alluded to earlier, version 18.1 is available. Those that already upgraded to 18.0 can upgrade at your leisure. Version 18.1 will get LL tests assigned to it, whereas version 18.0 will only get double-checks assigned. The deleting of v17 save files below 4.2M is fixed. I hope you didn't do as said in the whatsnew.txt, shouldn't it be KEEPING those below 4194304? 2) Only v17 save files below 4194304 are deleted. -- Henrik Olsen, Dawn Solutions I/S URL=http://www.iaeste.dk/~henrik/ Get the rest there. Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Re: Mersenne: A dreadful Virus called Milessa!
On Wed, 31 Mar 1999 [EMAIL PROTECTED] wrote: Gosh! I just read an artical about new virus called "Melissa". When a user opens this email in his or her MS Outlook, the MS Visual Basic macro virus automatically sends a copy of itself to the first 50 people in the user's address book. The subject heading reads, "Very important message from [user]", (user = the last person who unknowingly sent it.) It spreads like fire, from anyone who was unintentionally sent this email, opening this email will breed another 50 copies. I read it in England's Telegraph newspaper (31 March, 1999). Summery: dont open any messages with the "important message..." business in the heading. I just thought a bunch of emailers like you guys might need this info. Let me know if you find out anything about this virus. -oliver This is a report that would normally have triggered all my hoax detectors due to the total lack of references, but luckily I'd already been informed by a more reliable source. For more info and the straight dope, check http://www.cert.org/advisories/CA-99-04-Melissa-Macro-Virus.html -- Henrik Olsen, Dawn Solutions I/S URL=http://www.iaeste.dk/~henrik/ Get the rest there. Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Mersenne: Re: Is bug a hoax?
Hi all, At 06:45 PM 4/2/99 +0200, Henrik Olsen wrote: Somehow I find it suspicious that the assignments status report http://entropia.com/primenet/status.txt shows no change at all in the pattern of assignments, something that should have been immediately visible if ~1 exponents had been recycled for first time LL-testing The first task was to fix the program. Scott and I are now working out a plan to get the 1 affected exponents back in the queue. That should happen sometime over the next few days. There should be a slight uptick in double-check assignments that go out. Unfortunately, the server cannot contact the v17 clients and tell them to ditch their current assignments and get new ones. So only those that are running low on work will get double-check assignments. Best regards, George Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Re: Mersenne: IMPORTANT: BUG IN VERSION PRIME95 17
George, I have plenty of reasons to feel that you should not be so worried with what happened : - Since I joined GIMPS project more than three years ago, you always impressed me with your thorough work. You have proved several times your professionalism, up to the way you announced this bad news, honestly and humbly. - Don't forget your motto : 'just for fun'. A small bug in a program whose primary goal is to entertain all of us is nothing compared with e.g what happens now in Kosovo.. - Even the great Mersenne himself commited two bugs, by incorrectly 'proving' primality of M(67) and M(257). You have been wrong only once... George, the hardest is now behind us, let's discover M38 quickly and everything will be forgotten. Regards, Jean-Yves -Original Message- From: George Woltman [EMAIL PROTECTED] To: [EMAIL PROTECTED] [EMAIL PROTECTED] Date: 02 April 1999 01:07 Subject: Mersenne: IMPORTANT: BUG IN VERSION PRIME95 17 Hi all, Please forgive me. I'm terribly sorry. I've discovered a bug in version 17 of prime95 and its variants (ntprime, mprime, OS/2 version). All Lucas-Lehmer tests above 4,194,304 (except those that were done as a continuation of a v16 run) are no good. I feel sick. Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
RE: Mersenne: Re: Is bug a hoax?
The first task was to fix the program. Scott and I are now working out a plan to get the 1 affected exponents back in the queue. That should happen sometime over the next few days. There should be a slight uptick in double-check assignments that go out. Unfortunately, the server cannot contact the v17 clients and tell them to ditch their current assignments and get new ones. So only those that are running low on work will get double-check assignments. Would I be right in assuming that Primenet keeps track of which version was used to check in a certain result? If so, what about folks that manually check in numbers? Does one of those numbers besides the residue indicate version? And once all suspect results are identified, those exponents will be removed so they can be retrieved as LL tests rather than double-checks...yes? Otherwise, double-checking will take a while to get up to those numbers since the current range of double-checks being passed out are in the 2^2.6M range... And finally, is there a plan to send an email notice to everyone? We on this list found out, but alot of folks are probably running the software but aren't on the list...I know I was for quite some time. They might like to know that their current test needs to be restarted right away. I'm just full of questions... :-) Fortunately (?) they're turning off our building power this weekend so I was going to have to work on all my machines anyway... Aaron Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Re: Mersenne: Questions answered on v17 bug
George Woltman wrote:
The bug was in the routine mulmod which was supposed to compute a * b
mod c
The implementation was a rather sloppy:
unsigned long tmp;
tmp = a * (b 0x3FF);
tmp += ((a 10) % c) * (b 10);
return (tmp % c);
You can see in the first computation of tmp there will be an overflow
if
a exceeds 2^22 or 4194304. The new implementation is:
double tmp;
unsigned long q;
tmp = (double) a * (double) b;
q = (unsigned long) (tmp / (double) c);
return ((unsigned long) (tmp - (double) q * (double) c));
This implementation isn't perfect, but will work as long as a * b does
not exceed 53 bits.
This got me thinking, since I've had a use for modular multiplication in
some of the little programs that I've bee writing. Based on your code, I
wrote the following:
unsigned long mulmod(unsigned long a, unsigned long b, unsigned long n)
{
long double tmp, q;
tmp = a * (long double)b;
q = floorl(a * (long double)b / n);
return tmp - q * n;
}
In my testing, this appears to give the correct result for any 32-bit
values of a, b, and n, thanks to the 64-bit precision of Intel's 80-bit
floating point type. Is there anything wrong with this approach? It
depends on having a long double version of the floor function, which is
available on my Borland compiler.
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Mersenne: Goodbye...
After the latest two events, I am saying good-bye to Prime95. The latest rumors (?) caused some concern, but then I upgraded to version 18.1 and lost two months of work (it deleted the intermediate files). That did it. Ah, well, it has been fun for two years. I'll probably miss the little red icon -- for a while. Randy Given [EMAIL PROTECTED] http://members.aol.com/GivenRandy public key at http://members.aol.com/GivenRandy/pgpkey.asc Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Mersenne: Recent Happenings
Hi, I'd just like to chime in with what I'm sure must be the feelings of most of us here. We understand that accidents happen, bugs creep in, especially ones that are subtle and hard to detect. Without George's expertise and long hours spent programming and organizing the effort, very very few of us would be searching for Mersennes. It continues to be a highly enjoyable experience, so I want to take this opportunity to echo Robert, Jean-Yves, and others in saying Thank You George. Just For Fun, Chad Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
RE: Mersenne: Goodbye...
From: [EMAIL PROTECTED] After the latest two events, I am saying good-bye to Prime95. The latest rumors (?) caused some concern, but then I upgraded to version 18.1 and lost two months of work (it deleted the intermediate files). That did it. Ah, well, it has been fun for two years. I'll probably miss the little red icon -- for a while. Randy Given Hmmm...I'd ask you to reconsider. Remember, it's something to harness that extra computing power that otherwise is wasted. Sure, it's a setback to lose 2 months worth. Heck, I had NTPrime running on about 20 processors for quite a while and now those exponents 4.2M need to be rechecked, but what else would those computers do in their spare time? Heck, I had a terrible setback in regards to prime numbers, my own fault of course, but I still use what computers I'm *allowed* to use (heh) looking for primes. Just today I scrounged up a 200MHz PPro PC from spare parts at work and got it searching...it's fun in some strange way. So, I hope you'll reconsider. If not, I understand that too. Aaron Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
