20140711, 08:59  #1 
May 2007
Kansas; USA
3×5×701 Posts 
PFGW 3.6.x problems on small primes

20140711, 09:42  #2  
"Lennart"
Jun 2007
1120_{10} Posts 
Quote:
I am only sieving at this time.. I will not start LLR. Are you redoing them from scratch ? Lennart 

20140711, 10:52  #3  
May 2007
Kansas; USA
3×5×701 Posts 
Quote:
This was pointed out to me by Phillip (MagentaSunrise) after he searched S79 for n=25K50K and subsequently doublechecked all of the k's remaining to n=100. I think we'll also need to eventually look at many other largeconjectured bases, especially bases started since PFGW 3.6.0 was released. It's part of the reason that I doublechecked Riesel base 3 for k<1G to n=100K. Last fiddled with by gd_barnes on 20140711 at 10:54 

20140711, 14:52  #4  
"Mark"
Apr 2003
Between here and the
6,427 Posts 
Quote:


20140711, 19:16  #5  
May 2007
Kansas; USA
3·5·701 Posts 
Quote:
I suppose the best thing to do would be to get a copy of every version of PFGW since 3.3.6 and run each of them on the script for a few 1000 k's on S66/S79 to n=1000 to see if there are any other erroneous versions so that people get rid of or update their bad versions. (I know that x.x.0 versions are a little more susceptible to problems since x.x.1x.x.9 versions usually correct any bugs in extensive updates to the program.) I suspect that it may be related to updates in the GWNUM libraries. I know that George does extensive testing of those when doing LLR updates but testing on very small primes may not always be done. This is such a timeconsuming effort to either do or coordinate that I haven't wanted to take the time to do either. The error was first pointed out to me about 23 months ago. Last fiddled with by gd_barnes on 20140711 at 19:21 

20140711, 21:28  #6  
"Mark"
Apr 2003
Between here and the
191B_{16} Posts 
Quote:
Did this result in erroneously reported primes, missing primes, or both? From what you've written it appears that this only affects numbers with small n. Is that correct? If so do you know the upper bound of n that was affected? 

20140712, 00:11  #7  
May 2007
Kansas; USA
3×5×701 Posts 
Quote:
Probably anytime there is a change in GWNUM libraries and before releasing to the public, there should be a test run of several 100 or 1000 small primes (n<100 on many varying bases) to make sure nothing was affected at the small end of things. I reran a good chunk of those two bases up to n=1000, although it's such a mess I haven't made an attempt to change the CRUS pages. I think I can provide both the "bad" and "good" files of primes for you if you'd like. Last fiddled with by gd_barnes on 20140712 at 00:12 

20140712, 00:23  #8  
"Mark"
Apr 2003
Between here and the
1100100011011_{2} Posts 
Quote:


20140712, 00:30  #9  
May 2007
Kansas; USA
3×5×701 Posts 
Quote:
The comparison is a bit tricky because sometimes it would miss a prime for n=4 and then later find a prime for the same k for, say, n=500. Other times it would not find a prime at all for that k. Other times for another k it would have a "prime" for n=4 when in fact the "prime" was composite. It's a difficult task to sort out all of the scenarios, which is why I don't see any alternative but to start the bases completely over. Edit: Perhaps I can send you both the good and bad files and you can come up with an automated comparison so that we're more confident in what we're dealing with. Last fiddled with by gd_barnes on 20140712 at 00:33 

20140712, 17:21  #10  
Quasi Admin Thing
May 2005
967 Posts 
Quote:
However, before starting from scratch, I feel like we have to do following: 1. choose a base <1030 2. choose a conjecture <1000 3. find as many as possible versions of PFGW (both 32 and 64bit) 4. test the choosen conjecture in each available version of PFGW 32 bit* 5. test the choosen conjecture in each available version of PFGW 64 bit* * using the starting new bases script, going from n=1 to n=25000. 6. compare the different resultfiles to each other, to see wich files is simmilar and wich is different, thereby we can see wich versions of PFGW that is at least working similarly 7. create a klist with all k's <conjectured k 8. sieve the range of k's from n=1 to n=25000, using srsieve and sr2sieve 9. LLR test the remaining candidates, using LLR 3.8.9 and StopOnPrimedK=1 10. Compare the primelist made by LLR with the primelist made by PFGW 11. compare/verify the mob list made by PFGW (manually) 12. compare/verify the trivial factors list made by PFGW (manually) 13. by finish of compare, make an official zip package, with a verified safe version of PFGW wich has to be used when starting new bases 14. start a drive to start all bases onebyone from n=1 to n=25K (maybe the good folks at Primegrid can be of help here, since it could be a great PSA project)** ** This would mean, that everything is correct and doublechecked, such that future searchers should not be concerned about mallock material. Also it will make sure that no search ranges for the relative low bases with a very big conjecture is left unsearched for months or years at a time. Maybe if a drive is setup, we should have 2 users search the same range of k's. Even though it is no easy task to compare millions of lines, I think I'll be able to offer a helping hand if you need it. On a sad note, I just noticed that my R3 13G14G range was searched using PFGW 32bit version 3.6.3 ... so I guess that will make the range suspiscious... Take care Kenneth 

20140712, 17:53  #11 
May 2007
Kansas; USA
24423_{8} Posts 
Sounds great if someone has unlimited personal time to coordinate such an effort. I think this is something that we'll just have to do piecemeal as we have the time and inclination to do so. At some point, I think I'll need to add a doublecheck column to the CRUS pages so that we know what has been done.
As for R3 k=13G14G, can you provide me with a small list of primes, perhaps k=13G13.01G to n=10K or 25K using PFGW 3.6.3? I'll then run PFGW 3.3.6 or 3.4.1 against it and we'll compare the two. 
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