Awfully small factors....

[petrw1]

Some recently turned in Manual Testing factors are under 40 bits???

GrunwalderGIMP       Manual testing   128557967 F        Nov 19 2009  2:11AM   0.0   0.0000  58879548887                                  
GrunwalderGIMP       Manual testing   128556863 F        Nov 19 2009  2:11AM   0.0   0.0000  46280470681 
GrunwalderGIMP       Manual testing   128556803 F        Nov 19 2009  2:11AM   0.0   0.0000  762341841791

and many more at that time....

They are listed, valid factors but how is it that such small factors are being turned in now? This range was likely factored to that level a 'long' time ago.

[Batalov]

Ah, that's clear. These numbers already have aneven smaller factor, so for the search purposes they are eliminated. There used to be a configuration flag to report all factors or just one.

E.g.
M128557967 has a factor: 31882375817
M128557967 has a factor: 58879548887
M128557967 has a factor: 10081001540273

M128556863 has a factor: 3085364713
M128556863 has a factor: 46280470681

M128556803 has a factor: 80219445073
M128556803 has a factor: 762341841791

[Prime95]

Ugh, a bug in prime95's factoring code? A computer glitch at the time that range was factored? Maybe some other program did that low level factoring?

Try seeing if prime95 will find those factors.

If the problem is widespread, I'll have to do some statistical analysis to see what ranges need refactoring.

[Batalov]

Someone used
SendAllFactorData=0
in prime.txt?

[S485122]

Looking at what is in the database for one of those exponents, one can only conclude that another program than Prime95 was used :

Exponent Date found Bits Factor
128557967 2007-10-08 14:14 35 31882375817
128557967 2009-11-19 02:11 36 58879548887
128557967 2009-11-19 02:11 44 10081001540273
128557967 2009-11-19 02:11 63 5171044349132734223

Even with the (undocumented in 25.11) SendAllFactorData option Prime95 would only continue looking for factors in one bit level : it would look for smaller factors than the first one found. Another possibility are multiple Factor lines for one exponent, instead from factor from 0 to 64 bits one line per bit level...

Best thing would be to ask Gareth William or Grunwalder, the producer of those results. But his GIMPS referenced web page explains all :

In addition, I've been running my own searches for factors of Mersenne numbers, doing what is known as Lone Mersenne Hunting (or LMH). This searching is proving to be very successful: a summary page is available. Two different types of searches are being undertaken: for exponents without any known factors, I try to extend the range of possible factors that has been searched and hopefully find a factor (this is successful in about 5% of cases); for exponents with at least one known factor, I try to find additional factors by searching to higher limits (this is successful in about 29% of cases, with an average of 1.20 new factors for each successful case and including two cases where five new factors were found!). The number of "1st factors" claimed on the summary page is based on the very useful datafiles provided by Will Edgington. This work is not credited in the V4 PrimeNet statistics ...

So, don't worry George, it is no indication of a bug.

Jacob

[Batalov]

I also used to have a million factors submitted (with a small 64-bit 40-liner program), but now, a year had passed and they are gone from stats. I did submit multiples, though...

[petrw1]

Originally Posted by S485122

But his GIMPS referenced web page explains all :

Jacob

I don't see any reference to finding "small" factors in that excerpt; only that he is factor more and to higher bit levels

[petrw1]

Prime95 25.9B4 wouldn't let me refactor it to lower levels than it currently is...

[Main thread Nov 19 09:01] Mersenne number primality test program version 25.9
[Main thread Nov 19 09:01] Starting workers.
[Comm thread Nov 19 09:01] Registering assignment: Trial factor M128557967
[Comm thread Nov 19 09:01] URL: http://v5.mersenne.org/v5server/?v=0.95&px=GIMPS&t=ra&g=4f402bc7132e14b4bd6e989d4475e683&c=0&w=2&n=128557967&sf=20&ef=60&ss=959
[Comm thread Nov 19 09:01] RESPONSE:
[Comm thread Nov 19 09:01] pnErrorResult=40
[Comm thread Nov 19 09:01] pnErrorDetail=ra: trial factoring not required, exponent: 128557967, ef: 60
[Comm thread Nov 19 09:01] ==END==
[Comm thread Nov 19 09:01] 
[Comm thread Nov 19 09:01] PrimeNet error 40: No assignment
[Comm thread Nov 19 09:01] ra: trial factoring not required, exponent: 128557967, ef: 60
[Comm thread Nov 19 09:01] Done communicating with server.

[mdettweiler]

Originally Posted by petrw1

Prime95 25.9B4 wouldn't let me refactor it to lower levels than it currently is...

[Main thread Nov 19 09:01] Mersenne number primality test program version 25.9
[Main thread Nov 19 09:01] Starting workers.
[Comm thread Nov 19 09:01] Registering assignment: Trial factor M128557967
[Comm thread Nov 19 09:01] URL: http://v5.mersenne.org/v5server/?v=0.95&px=GIMPS&t=ra&g=4f402bc7132e14b4bd6e989d4475e683&c=0&w=2&n=128557967&sf=20&ef=60&ss=959
[Comm thread Nov 19 09:01] RESPONSE:
[Comm thread Nov 19 09:01] pnErrorResult=40
[Comm thread Nov 19 09:01] pnErrorDetail=ra: trial factoring not required, exponent: 128557967, ef: 60
[Comm thread Nov 19 09:01] ==END==
[Comm thread Nov 19 09:01] 
[Comm thread Nov 19 09:01] PrimeNet error 40: No assignment
[Comm thread Nov 19 09:01] ra: trial factoring not required, exponent: 128557967, ef: 60
[Comm thread Nov 19 09:01] Done communicating with server.

I could have sworn there was an option somewhere in prime.txt that let you tell Prime95 to keep looking even after finding a factor. That, combined with turning off PrimeNet communication, might do the trick.

[ATH]

Prime95 25.11.2 finds them when factoring offline:

UID: athath/work2, M128557967 has a factor: 31882375817
UID: athath/work2, M128557967 has a factor: 58879548887
UID: athath/work2, M128557967 has a factor: 10081001540273

UID: athath/work2, M128556863 has a factor: 3085364713

UID: athath/work2, M128556803 has a factor: 762341841791
UID: athath/work2, M128556803 has a factor: 80219445073

But there is no "ContinueFactoring=1" command like the existing "ContinueECM=1", so its hard to find more factors without manually doing upper ranges.

[S485122]

Originally Posted by petrw1

I don't see any reference to finding "small" factors in that excerpt; only that he is factor more and to higher bit levels

Higher than the first factors found.

For the exponent I cited you can clearly see a 35 bits factor found in October 2007 and three LARGER factors found by Gareth (they may be larger but are still small at 36, 44 and 63 bits.) The 36 and 44 bits factors certainly qualify as awfully small factors for ranges that have already been factored to 63 bits.

Jacob