Re: Mersenne: double-check mismatches
On Saturday 17 January 2004 02:32, Daran wrote: > On Thu, Jan 15, 2004 at 07:15:46PM +, Brian J. Beesley wrote: > > ...matching > > residuals mean that the chance of an error getting into the database as a > > result of a computational error is of the order of 1 in 10^20. > > That's per exponent, isn't it? The chance that one of the roughly quarter > million status-doublechecked exponents being in error is about five orders > of magnitudes higher. Sure. That's why I ran the project to triple-check a not inconsiderable number of smaller exponents where one (in some cases both) of the residues was reported to less than 64 bits, usually only 16. No discrepancies were discovered. > > Still acceptible, or at least a minor consern in comparison to the other > security issues. > It's easy enough - and computationally exceedingly cheap - to report more residue bits but, as you say, other issues are not so easy to fix. Regards Brian Beesley _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: double-check mismatches
On Thu, Jan 15, 2004 at 07:15:46PM +, Brian J. Beesley wrote: > ...matching > residuals mean that the chance of an error getting into the database as a > result of a computational error is of the order of 1 in 10^20. That's per exponent, isn't it? The chance that one of the roughly quarter million status-doublechecked exponents being in error is about five orders of magnitudes higher. Still acceptible, or at least a minor consern in comparison to the other security issues. > Regards > Brian Beesley Daran G. _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: double-check mismatches
On Thursday 15 January 2004 01:00, Max wrote: > Hello! > > Is any statistix on double-check mismatches available? > How often this happens? ~2% of all runs are bad. > > If my result get mismatch with some other's will I get any notice about > that? No. But you can check the database - any results in the file "bad" have been rejected because of a residual mismatch. > Can I learn which of my results were confirmed by others? Yes. Check the "lucas_v" database file. > > P.S. Having periodical problems with overheating (coolers become dusty) > causing ``roundoff'' etc. hardware errors in mprime, Can you not run a hardware monitor program based on lm_sensors so that an alarm sounds at a temperature below that which causes problems? Most P4 chipsets will also automatically throttle the CPU clock if/when overheating occurs, so you will be notified by increasing iteration times rather than errors. > I don't much believe in computational results unless they're confirmed > by several parties. This attitude is entirely reasonable for long runs given consumer-grade hardware. > BTW, how error-proof is mprime ? On its own, not particularly. The computational cost of reasonably robust self-checking would be too much to bear. However, given that independent double checks are run, the _project system_ is pretty good - matching residuals mean that the chance of an error getting into the database as a result of a computational error is of the order of 1 in 10^20. _Detected_ errors - roundoff or otherwise - are not a problem. It's the undetected ones which are dangerous. If you have any ideas about how to improve this, I'm sure that George will consider them. There _are_ significant weaknesses in the project - in particular there is a _possibility_ that forged double check results could be submitted - that is one reason why I'm trying to triple-check all the exponents where both tests were run by the same user. Yes, I'm aware that a determined person with a working forging formula could bypass that check, too, but we've got to start somewhere. Regards Brian Beesley _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
RE: Mersenne: double-check mismatches
> Is any statistix on double-check mismatches available? > How often this happens? See http://www.mersenneforum.org/showthread.php?s=&threadid=1116 Combined error rate is between 3 and 4% _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: double-check mismatches
On Wed, Jan 14, 2004 at 05:00:18PM -0800, Max wrote: > Is any statistix on double-check mismatches available? > How often this happens? About 0.5%, IIRC. /* Steinar */ -- Homepage: http://www.sesse.net/ _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: double-check mismatches
Hello! Is any statistix on double-check mismatches available? How often this happens? If my result get mismatch with some other's will I get any notice about that? Can I learn which of my results were confirmed by others? P.S. Having periodical problems with overheating (coolers become dusty) causing ``roundoff'' etc. hardware errors in mprime, I don't much believe in computational results unless they're confirmed by several parties. BTW, how error-proof is mprime ? Thanks, Max _ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
