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2008-01-17, 23:13   #177
gd_barnes

May 2007
Kansas; USA

10,357 Posts

Quote:
 Originally Posted by michaf Usually, taking a bigger range doesn't affect the speed too much. Then again, whenever you find a prime, the extra time is 'wasted'. I'd say that after n=0-100k, a good choice would be n=100-500k. Best would be to test-sieve a few ranges and see how it affects the speed

Agreed on the range to sieve. The speed varies by the square root of the n-range so n=100K-500K should sieve about 50% slower [1-1/sqrt(100K/400K)] than n=100K-200K. If you don't want that kind of slowdown, you could do n=100K-300K, which should sieve about 29% slower [1-1/sqrt(100K/200K)]. The main thing here is that on these low-weight k's, the chance of finding a prime in any n=2X range, i.e. n=100K-200K, is well under 50% so the bigger range is better. Clearly you'll want to break off pieces of the range and LLR them as you go while continuing to sieve the higher ranges.

About how to sieve: For 2 k's, you would generally use 2 instances of sr1sieve. But for 3 to ~50-100 k's, use sr2sieve on all of them. >~50-100 k's use srsieve for all sieving. There may be exception situations on 2 or 3 k's since that's kind of the dividing line on what to use. But sr1sieve running 1 k would have to be 3X as fast as sr2sieve running 3 k's, which seems unlikely in most situations. You might test it out to be sure and post back here what you find out.

Gary

2008-01-18, 00:43   #178
jasong

"Jason Goatcher"
Mar 2005

350710 Posts

Quote:
 Originally Posted by gd_barnes I just realized that I'll have a dual-core machine freed up later tonight. I'd like to fill in the 'factor holes' first so that it is cleanly sieved up to P=1T. That should take < 1 day. I'll then send the files to you for sieving to P=1.5T. Look for them sometime late Thurs./early Fri. Are you familiar with how to run sr2sieve? If not, I should mention that it doesn't remove candidates, it only writes out factors. I'm fine if you want to run the sieve and send me the factors. I can then remove the candidates using srfile. Gary
That'd be great. Thanks. And yes, I do know how to run sr2sieve.

I've removed factors in the past using srsieve, it's simply a matter of carefully reading the instructions. :)

2008-01-18, 01:08   #179
jasong

"Jason Goatcher"
Mar 2005

3×7×167 Posts

Quote:
 Originally Posted by Siemelink 342*27^36291+1 is prime. found PRP by LLR, proven with pfgw. I won't continue that range obviously. Has anyone ever found a PRP that turned out not to be prime after all? Willem.
I'm not familiar with the actual math, but I've heard that the bigger the number, the less likely it is to be a PRP that's not prime. In terms of the top-5000, it's probably next to impossible.

As Dr. Silverman would say: "Trust, but verify."(This applies to my assertion about PRPs, as well as the PRP itself)

Last fiddled with by jasong on 2008-01-18 at 01:09

 2008-01-18, 06:25 #180 mdettweiler A Sunny Moo     Aug 2007 USA (GMT-5) 3·2,083 Posts Riesel Base 30 k=25 sieving status: Currently at about 340G, planning to go to 600G. Should be done sometime next week (hopefully). It's running on an older machine that isn't on all the time.
 2008-01-18, 22:52 #181 gd_barnes     May 2007 Kansas; USA 101000011101012 Posts Sierp base 16 single-k reservations... Reserving Riesel base 16 k=2297, 2993, and 13854. I'll take them up to n=100K. If I find one for k=13854, that'll knock out the same k on base 4. If someone reserves Riesel base 4 k=13854, please let me know and we'll coordinate. My LLRing for base 16 to n=100K will have the effect of testing all of the even n's for base 4 up to n=200K. In this situation, I would usually suggest reserving and testing base 4 to n=200K to accomplish finishing both of them more easily but I figure I'll do it this way and knock both of them out if I find a prime. Gary
 2008-01-19, 06:24 #182 mdettweiler A Sunny Moo     Aug 2007 USA (GMT-5) 624910 Posts My 2nd Drive file will probably be done sometime tomorrow, so when that's done, I've decided I'll try some sieving for a change. I've decided to reserve the following Sierpinski Base 6 k's for sieving: 154797*6^n+1 157473*6^n+1 166753*6^n+1 168610*6^n+1 172257*6^n+1 I'm reserving all five of them for sieving in the range 30K
2008-01-19, 15:13   #183
mdettweiler
A Sunny Moo

Aug 2007
USA (GMT-5)

3·2,083 Posts

Quote:
 Originally Posted by Anonymous My 2nd Drive file will probably be done sometime tomorrow, so when that's done, I've decided I'll try some sieving for a change. I've decided to reserve the following Sierpinski Base 6 k's for sieving: 154797*6^n+1 157473*6^n+1 166753*6^n+1 168610*6^n+1 172257*6^n+1 I'm reserving all five of them for sieving in the range 30K
Hey Gary, it looks like you made an error on the Sierp. Base 6 page: You marked one more k than I had mentioned above as reserved by me. I didn't reserve 151003, just the above listed.

2008-01-19, 16:28   #184

Sep 2004
UVic

2×5×7 Posts
reservation complete

Quote:
 Originally Posted by tcadigan ... reserving: sieve-sierp-base28.txt
no primes found.

attached is results file.

reserving sieve-riesel-base13.txt
Attached Files
 lresults.txt (198.2 KB, 222 views)

 2008-01-19, 19:28 #185 michaf     Jan 2005 479 Posts Two small successes for Sierpinski 24: 20161*24^16932+1 is prime 26801*24^17390+1 is prime Including the MOB that leaves 168 sequences to eliminate (no prime upto 34.3K) I've now included the MOB into the main files.
 2008-01-19, 20:28 #186 Xentar     Sep 2006 101110112 Posts Ok people, I made some performance tests for sieving sierp-base 17. The software I used: Windows XP Pro 32 bit srsieve 0.6.10 sr1sieve 1.2.6 sr2sieve 1.6.18 hardware: Intel C2D E6600 @2.4 GHz results: First, I used srsieve to create a sieve file and sieve it till p=1G. n-range = 100,000 - 1,000,000 srsieve started with ~800 kp/s. At the end, it got ~930 kp/s Then I used srfile to convert this sieve file to ABCD format (for use with sr2sieve) and three NewPGen files (for use with sr1sieve) sr1sieve (single k): the speed varied between 6.8 Mp/s and 7.5 Mp/s sr2sieve (all three k together): speed between 2.7 MP/s and 3.2 MP/s I think, it varies so much, because it was refreshed for every factor found (almost every second), but I can say, that sieving all three k together is faster, than every k alone.
 2008-01-19, 20:34 #187 em99010pepe     Sep 2004 283010 Posts Now try sr2sieve 1.7.5 version....

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