Double-checking with PFGW - Page 5

gd_barnes · 2010-09-16, 20:22

I'm curious: Have any new primes been found with version 3.3.6 that were previously missed by version 3.3.4?

gd_barnes · 2010-09-16, 20:26

Xentar, to add a little more to what Mark said, we are only asking that people doublecheck the k's where there is no prime, i.e. k's remaining. We are not requiring that the lowest prime be found for each k so it is unnecessary to doublecheck k's with primes. That should make the doublecheck of your S17 effort not too bad, especially since the remaining k is very low weight.

rogue · 2010-09-16, 21:05

Quote:

Originally Posted by gd_barnes

I'm curious: Have any new primes been found with version 3.3.6 that were previously missed by version 3.3.4?

The only ones I have found to date were ones that I found when testing k*b^b+/-1 numbers. Other primes that I found were missed by older versions of PFGW. PFGW 3.3.4 would have found them. There were some issues with small FFTs that George fixed in gwnum 25.14, which PFGW first used in v3.3.3. I have not gone back to 3.3.3 to see if they were missed there.

I have discovered other k*b^n+/-c numbers where the residues changed between 3.3.4 and 3.3.6 due to the FFT size change, but none of those were prime. I don't want anyone to think that the problem is limited to k*b^b+/-1 numbers only.

I think it is possible that other primes were missed by 3.3.3 and earlier that would have been found by 3.3.4. I would not have believed that unless I found the undiscovered primes. Eventually it would probably behoove this project (and others) to retest all k*b^n+/-c for remaining k and n < 25,000 with PFGW 3.3.6. I will not start such an effort though because it is too massive. Now if I had 1000 cores at my disposal, then I might change my mind.

Siemelink · 2010-09-16, 21:14

I've double checked the Riesel 36s that I earlier took to n = 100,000.
8363*36^n-1
42227*36^n-1
56093*36^n-1
96497*36^n-1
108439*36^n-1
112997*36^n-1
115883*36^n-1
116329*36^n-1

There were some different FFTs, only with k = 8363. But no new prime...

Willem.

rogue · 2010-09-17, 02:00

Gary, since you are a moderator, could you update this post, http://www.mersenneforum.org/showpos...0&postcount=17 to reflect what hasn't been checked for re-testing? I hope to take out as many as I can this weekend.

KEP · 2010-09-17, 11:46

Regardin S383, I did a full doublecheck to n=24K, for all 48 k's remaining. There were no difference in the residuals printed by PFGW version 3.3.4 and the residuals printed by PFGW version 3.3.6! I had about 9300 tests for n>24K for S383, I did an -F comparisation, and none was found to be using a different FFT length when running PFGW 3.3.6 compared to the prior versions. So for the next couple of weeks I'm focusing on getting S383 to n=50K, before resuming S58 to n=125K!

And again to be clear, I'm not cancelling any work, however if a prime is missed at n<=1K, it just makes no sence to test that k into the millions before it finally makes a prime, that would really be a waste of resources. Well thats just my two cents. Mark thanks for your DC effort on S58 and S70. Continuing happily with the PFGW 3.3.6 version.

Take care everyone

KEP

rogue · 2010-09-17, 14:44

I am going to look for retests for all Riesel bases >= 800. I have already looked at n < 1000 for the remaining k for those bases. I'll provide the results and stats when it has completed. I'm sieving at the moment and thus don't know how many retests are required.

rogue · 2010-09-20, 15:23

Quote:

Originally Posted by rogue

I am going to look for retests for all Riesel bases >= 800. I have already looked at n < 1000 for the remaining k for those bases. I'll provide the results and stats when it has completed. I'm sieving at the moment and thus don't know how many retests are required.

I have completed sieving and have some stats. Overall I am checking 58 bases. I need to retest about 5.75% of the tests, 19,062 of 331,392. For some bases I over-sieved and for others I under-sieved. On average I sieved to about 1e10, which is a little deeper than I actually needed to sieve.

The base with the most tests was 999, with 58199 tests after sieving, but that base only yielded 21 retests. I had one base, 931, with 0 retests and a few other bases with less than 10. The base with the highest percentage of retests was 812, with 1046 of 2667 (39.22%) needing to be retested. Base 815 has the most retests (1596 of 5294, 30.15%). I expect base 1019 to take the longest to retest as there are 207 retests for n > 114,000.

rogue · 2010-09-20, 19:45

I'm also taking all Sierpinski bases >= 800. I've double-checked to n=500 and am in the process of sieving. Fortunately the nastiest bases, 928 and 999 have well < 1% retesting needed, so I won't sieve very deeply for them.

gd_barnes · 2010-09-21, 07:29

Mark, I'm curious: Can you post primes that you found with PFGW 3.3.6 that were missed with 3.3.4? I haven't seen any yet. I think you said that none have been found except in the k*b^b-/+1 search and that thread was too long for me to dig through. The only issue that I have with that statement is that I ran the Sierp side of that search for k<=10K and b<=1K with both versions of PFGW and posted the primes for Karsten to add to his page. It was a complete doublecheck (not just the ones with fftlen differences). No differences in primes were found. (I didn't output residues.)

Were the missing prime(s) found on the Riesel side of the kbb1 search or for k>10K or for b>1K ? I'm very curious as to where these missing primes will pop up.

3 more things:

1. Without a Linux version, my testing is continuing with 3.3.4.
2. We'll need to add R51 to n=3K as well as new bases that I've been running to n=25K that were done since the time that you made your list to the bases that need to be checked.
3. For lack of wanting to administer another effort here, I'm dragging my feet on keeping track of what's been done and is left to do. I'll likely get more motivated when a missing prime is found.

kar_bon · 2010-09-21, 08:32

Quote:

Originally Posted by gd_barnes

Were the missing prime(s) found on the Riesel side of the kbb1 search or for k>10K or for b>1K ?

The candidates during testing k*b^b+1 were:

Code:

1000000006:P:1:619:1
9238 619
1000000006:P:1:626:1
9276 626
9876 626
1000000006:P:1:627:1
7504 627
8004 627
9056 627
9256 627
1000000006:P:1:635:1
9386 635
1000000006:P:1:650:1
8619 650
9732 650

What I've done was, comparing the results with LLR 3.8.1, pfgw 3.3.4 and pfgw 3.3.6 where I found errors with those pairs before.

Results:
- LLR 3.8.1: none of the candidates were found PRP/prime (ERROR: ROUND OFF for 9876*626^626+1)
- pfgw 3.3.4: same here, all composite
- pfgw 3.3.6: 9238*619^619+1 is 3-PRP, others composite

The Riesel-side I've not checked yet.

2010-09-16, 20:26	#46
gd_barnes May 2007 Kansas; USA 101·103 Posts	Xentar, to add a little more to what Mark said, we are only asking that people doublecheck the k's where there is no prime, i.e. k's remaining. We are not requiring that the lowest prime be found for each k so it is unnecessary to doublecheck k's with primes. That should make the doublecheck of your S17 effort not too bad, especially since the remaining k is very low weight. Last fiddled with by gd_barnes on 2010-09-16 at 20:26

2010-09-21, 07:29	#54
gd_barnes May 2007 Kansas; USA 101·103 Posts	Mark, I'm curious: Can you post primes that you found with PFGW 3.3.6 that were missed with 3.3.4? I haven't seen any yet. I think you said that none have been found except in the kb^b-/+1 search and that thread was too long for me to dig through. The only issue that I have with that statement is that I ran the Sierp side of that search for k<=10K and b<=1K with both versions of PFGW and posted the primes for Karsten to add to his page. It was a complete doublecheck (not just the ones with fftlen differences). No differences in primes were found. (I didn't output residues.) Were the missing prime(s) found on the Riesel side of the kbb1 search or for k>10K or for b>1K ? I'm very curious as to where these missing primes will pop up. 3 more things: 1. Without a Linux version, my testing is continuing with 3.3.4. 2. We'll need to add R51 to n=3K as well as new bases that I've been running to n=25K that were done since the time that you made your list to the bases that need to be checked. 3. For lack of wanting to administer another effort here, I'm dragging my feet on keeping track of what's been done and is left to do. I'll likely get more motivated when a missing prime is found. Last fiddled with by gd_barnes on 2010-09-21 at 07:34*

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2010-09-16, 20:22	#45
gd_barnes May 2007 Kansas; USA 101·103 Posts	I'm curious: Have any new primes been found with version 3.3.6 that were previously missed by version 3.3.4?

2010-09-17, 02:00	#49
rogue "Mark" Apr 2003 Between here and the 2⁴×397 Posts	Gary, since you are a moderator, could you update this post, http://www.mersenneforum.org/showpos...0&postcount=17 to reflect what hasn't been checked for re-testing? I hope to take out as many as I can this weekend.

2010-09-17, 11:46	#50
KEP Quasi Admin Thing May 2005 2·3·7·23 Posts	Regardin S383, I did a full doublecheck to n=24K, for all 48 k's remaining. There were no difference in the residuals printed by PFGW version 3.3.4 and the residuals printed by PFGW version 3.3.6! I had about 9300 tests for n>24K for S383, I did an -F comparisation, and none was found to be using a different FFT length when running PFGW 3.3.6 compared to the prior versions. So for the next couple of weeks I'm focusing on getting S383 to n=50K, before resuming S58 to n=125K! And again to be clear, I'm not cancelling any work, however if a prime is missed at n<=1K, it just makes no sence to test that k into the millions before it finally makes a prime, that would really be a waste of resources. Well thats just my two cents. Mark thanks for your DC effort on S58 and S70. Continuing happily with the PFGW 3.3.6 version. Take care everyone KEP

2010-09-17, 14:44	#51
rogue "Mark" Apr 2003 Between here and the 14320₈ Posts	I am going to look for retests for all Riesel bases >= 800. I have already looked at n < 1000 for the remaining k for those bases. I'll provide the results and stats when it has completed. I'm sieving at the moment and thus don't know how many retests are required.

2010-09-20, 19:45	#53
rogue "Mark" Apr 2003 Between here and the 2⁴×397 Posts	I'm also taking all Sierpinski bases >= 800. I've double-checked to n=500 and am in the process of sieving. Fortunately the nastiest bases, 928 and 999 have well < 1% retesting needed, so I won't sieve very deeply for them.