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Old 2007-07-24, 21:57   #1
petrw1
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Default Can anyone explain 'iterations' for factoring?

We typically see numbers between 1 and 16 under iterations for factoring; however there is the odd exception where the number of iterations is significantly higher:

For example:
43163371 F 63 10 1.5 0.8 60.8 23-Jul-07 09:13 22-Jul-07 03:33 jamamastaha Rusada65

43159609 F 63 10851596 1.7 0.3 60.3 22-Jul-07 22:42 21-Jul-07 22:42 Team_Bundu GordonVista

Last fiddled with by petrw1 on 2007-07-24 at 21:58
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Old 2007-07-30, 19:45   #2
WsF
 
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Unhappy 16 series, 16 iterations

Numbers 1..16 are can be explained if George W. still uses his trick: there are 16 numbers between 0 and 120=2^3*3*5 mutually prime with 3,5 and equal +/-1 mod 8: 1,7,17,23, 31,41,47,49, 71,73,79,89, 97,103,113,119. Possible divisors (in a form 2kp+1) belong to one of these 16 series and the numbers you ask indicate them, I think.

I have completely no idea on 10851596.
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Old 2007-07-31, 05:01   #3
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Quote:
Originally Posted by WsF View Post
Numbers 1..16 are can be explained if George W. still uses his trick: there are 16 numbers between 0 and 120=2^3*3*5 mutually prime with 3,5 and equal +/-1 mod 8: 1,7,17,23, 31,41,47,49, 71,73,79,89, 97,103,113,119. Possible divisors (in a form 2kp+1) belong to one of these 16 series and the numbers you ask indicate them, I think.
Makes sense but if I am factoring for 63 bits, then 64, then 65 ... to 68 should I not see iterations 1 - 16 for each of these bits?
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Old 2007-07-31, 08:17   #4
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Quote:
Originally Posted by petrw1 View Post
Makes sense but if I am factoring for 63 bits, then 64, then 65 ... to 68 should I not see iterations 1 - 16 for each of these bits?
Perhaps you would if the computer reported progress really, really often? Automatic check-in can't be more often than daily.

43159609 is interesting... that status data is probably showing it being LL tested, but only TFd to 63 bits. The latest GIMPS nofactor data, from about the same time as the OP, has it TFd to 67 bits - better but not good enough. It ought to be done to 68 bits. This might explain why it's now not in either cleared.txt or status.txt (dated 31 Jul 2007 07:00 UTC). It's probably available for the last bit of TF, despite having completed LL testing.
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Old 2007-07-31, 08:57   #5
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Thumbs up

Quote:
Originally Posted by markr View Post
Perhaps you would if the computer reported progress really, really often? Automatic check-in can't be more often than daily.
You are right!
Each range (to 63, 64, and so on) is proceeded from 1 to 16. At least it was when I was more interested in algorithms and methods used by George.
If you use Manual Communications just before and just after switch from 2^b to 2^(b+1) you can see (in your individual report at the PrimeNet) that iteration number has dropped from, say, 15 to 2.
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Old 2007-07-31, 09:18   #6
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Lightbulb PS

It is why Prime95/mprime does not determine the smallest factor as a rule. After finding a factor = 47 mod 120, e.g., it does not work on further possiblities (49, 71, ... mod 120). Remember that GIMPS means "Mersenne Prime Search". This project organized by G. Woltman does not bother with factoring composite Mersenne numbers, but some other projects do.
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Old 2007-07-31, 16:04   #7
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From my experience, the 1 - 16 method was used in version 24 and prior. It would cycle through 1 through 16 for each bit level. Version 25 now shows the progress at each bit level in a manner similar to the progress of LL tests. That is in absolute numbers up to the the value of M being tested.
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Old 2007-08-10, 23:47   #8
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Quote:
Originally Posted by petrw1 View Post
43159609 F 63 10851596 1.7 0.3 60.3 22-Jul-07 22:42 21-Jul-07 22:42 Team_Bundu GordonVista
Woot! My team stats have been quoted on this forum for the first time!!

is it because that pc in my team is running v25.3?
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Old 2007-08-11, 18:28   #9
petrw1
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Well this does support "monst" suggestions that V25 shows iterations differently ... not 1-16 but rather 1 - P.
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