mersenneforum.org Riesel Primes k*2^n-1, k<300 [Was "k=1"]
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2003-12-22, 14:22   #1
wpolly

Sep 2002
Vienna, Austria

DB16 Posts
Riesel Primes k*2^n-1, k<300 [Was "k=1"]

<Edit>Links and info posted by Kosmaj on May 12, 2004. Updated Jan 23, 2007.
Quote:
</Edit>

Orginal post by wpolly:

Have anyone considered about the most "basic" of the 15k's - 15?
I'm thinking about 15*2^n-1 primes (or other low k such as 75 165 225).

Those 15k's only completed to 10000 according to 15k stats page.
Anyone interested?

Last fiddled with by Kosmaj on 2007-01-23 at 19:52

 2003-12-22, 17:41 #2 jocelynl   Sep 2002 2·131 Posts Thanks for the link wpolly. I'll update the stats with the new stuff. k=15 is not a prone prime sequence. but if you wish, the stats would be helpfull. Joss L15.
 2004-03-25, 19:36 #3 robert44444uk     Jun 2003 Oxford, UK 111011100002 Posts k=1 Since the new LLR is 400% faster then looking at this series (15*2^n-1) makes an awful lot of sense. In fact I started my main machine sieving to 1 million immediately. After a week the sieve should be nice and lean. The reason for picking this low is because the speed up will work on SSE2 apparently. I looked at this series as part of my primoproth search but gave up because it was so unprime up to n=100000, but if you are looking for big primes.... Robert Smith
 2004-03-26, 01:42 #4 jocelynl   Sep 2002 2×131 Posts Hi Robert, I'm already working on it up to 150k for the complete sequence. So it's all yours from that point. Joss
 2004-03-27, 09:06 #5 robert44444uk     Jun 2003 Oxford, UK 24×7×17 Posts n=1 Joss Thank you for telling me this, saves half a day! The sieve is reducing my candidates still at an alarming rate, and there will be very few candidates left to use this blindingly fast software on! Forecast between 100000 and 200000 ... 6, 200000..1000000 6 more. This is gut feel, no maths involved. Regards Robert Smith
 2004-03-28, 09:50 #6 jocelynl   Sep 2002 2·131 Posts Robert I'm all done to 150k. It might be interesting to team test this one. How far are you at sieving? Joss
 2004-03-30, 19:12 #7 robert44444uk     Jun 2003 Oxford, UK 190410 Posts 1 Joss I had to go away for a few days, and I started testing the number. I found two between 150 and 212K. How many did you find between 100 and 150K? I would guess 4. Disappointingly the LLR and the NewPgen sieve seem to compete for computer time in an inefficient manner. So the sieve is not as far advanced as I had hoped, only at 32 bn so far. But of course, now I am testing the numbers! So I have stopped that, and will concentrate on sieving from 212000 to 1 million, until I only get one candidate sieved in approximately 4 minutes. I think there are not enough people doing 15K to divert them from other tasks right now, especially as the other small numbers are begging to be worked on. But I am willing to share the sieve results if people are interested. I can't be expected to do much for this group, as I am horribly busy in the real world at the moment. So someone else will have to organise it. Regards Robert Smith
 2004-03-31, 08:08 #8 Kosmaj     Nov 2003 1110001001102 Posts Hello Robert, Congrats to you and Slash Dude on your new primes! Can somobody post exe times/cpu info of the new LLR for various exponents around n=200,000. Some exe times are given in the 3-2-1 forum but for much higher exponents and without cpu info, so they are not so useful. Have been thinking to try one small k myself but don't know which one...
2004-03-31, 18:12   #9
Thomas11

Feb 2003

1,907 Posts

Quote:
 Originally Posted by Kosmaj Can somobody post exe times/cpu info of the new LLR for various exponents around n=200,000. Some exe times are given in the 3-2-1 forum but for much higher exponents and without cpu info, so they are not so useful. Have been thinking to try one small k myself but don't know which one...
Seems that a few more people are testing small k's now, using the new LLR ...

For k=5 or k=7 my AthlonXP 2400+ (2 GHz) takes about 2 minutes for a test around n=200000. But I've found that only for the smallest values of k (e.g. 5, 7, 9 and may be 11) LLR behaves like for k=3. For somewhat larger k it seems that the new LLR switches much earlier to larger FFT-lengths, e.g. testing k=29 for a given n takes almost twice the time as testing the same n for k=3.

Last year I talked with Paul Underwood about extending the 321search project to k=5 and k=7, and I have already sieved k=5 and k=7 for n=191500-1000000 up to about p=300 billion. This is far from being complete, but at the moment I don't have the time and computer power to continue this work. So, I could send you the sieve files, if you're interested.

Just one last note:
Please inform Wilfried Keller http://www.prothsearch.net/riesel2.html about any ranges you have tested and the primes you have found (if any), to keep his list of primes for k<300 current and to avoid others from double and tripple testing empty ranges. It seems to me that quite a lot of k's have already been tested up to about n=400000 or 500000 by some Proth.exe users but without giving Wilfried Keller the information about the ranges they did.

-- Thomas.

2004-03-31, 18:46   #10
ET_
Banned

"Luigi"
Aug 2002
Team Italia

22×1,193 Posts

Quote:
 Originally Posted by Thomas11 Just one last note: Please inform Wilfried Keller http://www.prothsearch.net/riesel2.html about any ranges you have tested and the primes you have found (if any), to keep his list of primes for k<300 current and to avoid others from double and tripple testing empty ranges.
So I assume that Wilfried Keller has been contacted for 321 project.

Luigi

Last fiddled with by ET_ on 2004-03-31 at 18:46

 2004-03-31, 20:57 #11 SB2     Jul 2003 11410 Posts If it has not already been done or started I am preparing to sieve k=9 from 191500-1000000. or would it be better to continue the sieving of 5 and 7? Last fiddled with by SB2 on 2004-03-31 at 21:03

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