mfaktc: a CUDA program for Mersenne prefactoring

[Prime95]

Originally Posted by Ungelovende

M222xxxxxx from 2^64 to 2^71
mfaktc 0.17
Win7 64/gtx570x2
ca 7750 tests - 121 factors found

That is scary -- expected is 848 factors

[davieddy]

Hmmm.
Lost here.
"Test" means?
7750/67 = 116

David

[Ungelovende]

Originally Posted by Prime95

That is scary -- expected is 848 factors

I counted 2^64 to 2^65 as one 'test'. 2^65 to 2^66 on the same exponent as another 'test'

[Prime95]

Originally Posted by Ungelovende

I counted 2^64 to 2^65 as one test. 2^65 to 2^66 on the same exponent as another test

Whew!! You did get the expected number of factors. Maybe Xyzzy is just an unlucky bloke. Let's see how his next batch does.

[davieddy]

Originally Posted by Prime95

Whew!! You did get the expected number of factors. Maybe Xyzzy is just an unlucky bloke. Let's see how his next batch does.

I was half hoping for a compliment on my "fielding"
skill there.

David

[nucleon]

Ok some stats from me. The current batch I'm looking at is 380M, I've broken down the range to 3x seperate sections:

a) 2^65 to 2^74
b) 2^74 to 2^76
c) 2^76 to 2^77

I find doing this method gives the best efficiency of compute time with my hardware.

So across my farm, no-factor/factor-found is:

a) 612/85
b) 170/1
c) 342/5

Why (c) is greater than (b), is initially I did other combos before I settled in on this plan. (i.e. 75-76, and 73-76), but I always did 76-77.

(c) seems to fit in with the 1 in 70 expectation although it might be low sample size. I've leave it up to readers with more maths ability than me to work out if (a) is within expectations.

I have 11x instances of mfaktc running, so stats are a little hard to collate :)

I've been running since April. If I have time I can get some stats on another range I looked at - 100M.

-- Craig

[Xyzzy]

Maybe Xyzzy is just an unlucky bloke. Let's see how his next batch does.

The attached image summarizes our work to date, including today's dump. We will attach the raw data in the next post.

[Xyzzy]

.

[ckdo]

Some more data...

 Range start |   Range end | Level | Tests | Factors | 1 / ...
-------------+-------------+-------+-------+---------+---------
  27,270,697 |  28,129,921 | 67-68 | 3,702 |      38 |  97.42
  29,132,821 |  29,687,591 | 66-67 | 1,419 |      12 | 118.25
  29,132,821 |  30,757,057 | 67-68 | 1,790 |      17 | 105.29
 - - - - - - + - - - - - - + - - - + - - - + - - - - + - - - -
  27,270,697 |  30,757,057 | total | 6,911 |      67 | 103.15
-------------+-------------+-------+-------+---------+---------
  40,149,029 |  47,437,847 | 68-69 |   690 |      14 |  49.29

P-1 had not been done on any of the 690 exponents from the last range but on all from the other ranges.
A test would be a single bit level, obviously. I have no idea why the last range yielded so many factors.

Originally Posted by Prime95

Maybe Xyzzy is just an unlucky bloke.

I've had a streak of 863-or-some-such NF results once. Chat hippens.

[TheJudger]

Originally Posted by Xyzzy

1:115 here.

53M range. 69 to 70 or 70-71.

The sample size is > 9000 tested.

Xyzzy: I did a quick view to your results.txt posted on June 14th. I've focused on the M53.xxx.xxx exponents and checked the exponent status of the first 4 no factor M53.xxx.xxx: all of tham had P-1 done before your TF attempt to 2^70.
http://mersenne.org/report_exponent/...&B1=Get+status

What is the expected factor rate once P-1 has been done with reasonable B1/B2 bounds?

Oliver

[TheJudger]

Xyzzy, there are two things that I recommend to you if you think something is broken.

1. run the long selftest (mfaktc.exe -st) under the same circumstances as your daily work (number of instances, settings in mfaktc.ini, ...)
2. "rediscover" some allready known factors which were initially not discovered by mfaktc.
   E.g. yesterday I ran some of my recent P-1 factors in the M53.xxx.xxx range (23 factors from 2^68 to 2^71) with 0.17. I did "full length runs", not like the selftest just a small range in the class where the factor falls in. Everything worked fine.

Oliver