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rebirther 2015-12-10 19:53

Sieving for CRUS
 
Hi Followers,

If someone is able to sieve some S/R Bases from 25-100k this would be great. Also 100-200k and 200-400k are welcome. I am out of running these ranges soon in BOINC and I don't want to lose time. Thx in advance!

See recent posts in this thread for incomplete sieving reservations. See completed sieve files in the right-hand column of our reservations pages here:
[url]http://www.noprimeleftbehind.net/crus/Riesel-conjecture-reserves.htm[/url]
[url]http://www.noprimeleftbehind.net/crus/Sierp-conjecture-reserves.htm[/url]

gd_barnes 2015-12-10 21:12

[QUOTE=rebirther;418837]Hi Fellowers,

if someone is able to sieve some S/R Bases from 25-100k this would be great. Also 100-200k and 200-400k are welcome. Iam out of running these ranges soon in BOINC and I dont want to loose time. Thx in advance![/QUOTE]

My suggestion is to sieve some of the lowest difficulty bases as shown here:
[URL]http://www.noprimeleftbehind.net/crus/vstats_new/crus-unproven.htm[/URL]

Most of them will be 100-200k or 200k-400k. There are a lot of bases in that area that can more easily be proven or reduced to 1k or 2k remaining by BOINC.

LaurV 2015-12-11 06:30

Ok, can you tell me one base I could sieve, preferable sr1sieve or sr2sieve job, the limits to go to (about) and the time frame when you need it, and I can allocate some resources to it.

wombatman 2015-12-11 06:34

I'm sieving R347 (with its remaining k of 22) from n=200k to 400k. Not quite to P=1e12 yet, at which point I'll run a PRP test to get a feel for how far I need to sieve.

gd_barnes 2015-12-11 10:08

[QUOTE=LaurV;418892]Ok, can you tell me one base I could sieve, preferable sr1sieve or sr2sieve job, the limits to go to (about) and the time frame when you need it, and I can allocate some resources to it.[/QUOTE]

Using that list in the link that I posted above, the lowest difficulty bases are S428, S638, and S332. (Wombatman is doing R347.) I'd suggest starting with S428 for n=200k-400k.

LaurV 2015-12-11 10:32

[QUOTE=gd_barnes;418905]Using that list in the link that I posted above, the lowest difficulty bases are S428, S638, and S332. (Wombatman is doing R347.) I'd suggest starting with S428 for n=200k-400k.[/QUOTE]
Ok, sieving S428 for n>200k for a while, to see what's going on. Starting in one hour. Do you need factors file?

gd_barnes 2015-12-11 10:56

[QUOTE=LaurV;418907]Ok, sieving S428 for n>200k for a while, to see what's going on. Starting in one hour. Do you need factors file?[/QUOTE]

No

unconnected 2015-12-11 11:04

[QUOTE=rebirther;418837]Hi Fellowers,

if someone is able to sieve some S/R Bases from 25-100k this would be great. Also 100-200k and 200-400k are welcome. Iam out of running these ranges soon in BOINC and I dont want to loose time. Thx in advance![/QUOTE]

I have sieve file for S333 100K-250K, but sieve limit is only 1T. Will sieve deeply and send file to Gary.

MyDogBuster 2015-12-11 11:54

Check for doubles
 
People should check when starting a sieve for a base and range to see if the other side (Riesel or Sierp) has the same base with the same range and sieve them together. Saves time and resources.

I'll be working on the 25K-100K range doing the doubles first.

We don't take sieving reservations so using this thread to give a general area of work would help out a bit.

LaurV 2015-12-11 14:21

R428 seems proven, which saves me of the troubles to learn how use srXsieve to sieve both sides in the same time... :razz:

LaurV 2015-12-13 04:31

S428 200k<n<1M sieved to 2e12 (it was faster than I expected). At this score, I have ~125 seconds per factor, which would mean ~1000 seconds per factor in the 200k-300k range. Some cllr test in the same cpu says about 1800-2000 seconds for one test.

There are <7500 candidates remaining in 200k<n<1M.

[B]Question for the people knowing more about this subject: how much further should I go with sieving? And should I post the file here (~70kB) or send it to Gary?[/B]

---------------

In the same time I ran cllr in a different core for 8*428^n+1 for n to about 70k (continuing) - this is a doublecheck. [B]Gary, do you need residue file for DC purposes?[/B]

--------------

I also ran low-sieving and cllr for all other k's (as there are only 9 all together) for n>=2, as I just didn't like those numbers being prime for n=1. :razz: This is for the category "futile work", but it still can be posted like a puzzle. I found primes for n higher than 1 for all of them, except 2 and 6, but 6 is eliminated by algebraic factorization, it seems that all of them are divisible by 7. So here the primes with higher n:
[CODE]
2*428^1+1 = 857 is prime! (trial divisions)
5*428^1+1 = 2141 is prime! (trial divisions)
9*428^1+1 = 3853 is prime! (trial divisions)
3*428^2+1 = 549553 is prime! (trial divisions)
7*428^2+1 = 1282289 is prime! (trial divisions)
9*428^3+1 = 705624769 is prime! (trial divisions)

[COLOR=Red][COLOR=Red]1*428^32+1 is prime! (85 decimal digits) Time : 9.273 ms.[/COLOR]
[/COLOR][COLOR=Red][COLOR=Red]3*428^15+1 is prime! (40 decimal digits) Time : 9.067 ms.
[/COLOR]4*428^14+1 is prime! (38 decimal digits) Time : 13.575 ms.
[/COLOR][COLOR=Red]5*428^21+1 is prime! (56 decimal digits) Time : 9.341 ms.[/COLOR]
[COLOR=Red]7*428^20+1 is prime! (54 decimal digits) Time : 9.544 ms.
9*428^1665+1 is prime! (4383 decimal digits) Time : 156.265 ms.
[/COLOR]
[/CODE]Now, the "puzzle" is that I didn't find any prime for k=2, although I sieved to 1T and I cllr it to n=69133 - still running.

(I am not so happy with the prime for k=4 also, as that is long known, and not a "new find", hehe, but I didn't do any action in that direction. :razz:)

One outcome from this futile playing with numbers is that I uncovered a small bug in cllr. My first sieving file was including 10*428^n+1 too, and it was sieving from n=0, therefore after srsieve kept 10*428^0+1 (which is prime) and eliminated all the other, so in the resulted sieved file (I stopped srsieve at 1e8 and continued with sr2sieve, then split and used sr1sieve for 2 and 8) - so in resulted file after first application of the srsieve, the 2*428^1+1 (=857, prime) followed after 10*428^0+1 (=11, also prime). In this very particular situation, cllr is testing the first one, and says it's prime, but is skipping the other one (i.e. misses the prime 857). Now I know this is a buggy situation, which will never happen in real life, but I wonder which other primes it can miss...


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