mersenneforum.org Combine sieving with SoB?
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 2005-07-07, 01:28 #1 Mystwalker     Jul 2004 Potsdam, Germany 33F16 Posts Combine sieving with SoB? Hi there! Currently, over at SoB, there is a big effort on the way to sieve all candidates with n < 50M (instead of n < 20M), as this is supposed to be the optimal sieving range. They will soon reach 100T with a recheck (991 < n < 50M) and it could be possible to combine PSP and SoB searches afterwards, doing both to 50M. The corresponding thread: http://www.free-dc.org/forum/showthr...&threadid=9663
 2005-07-07, 04:31 #2 Citrix     Jun 2003 22·397 Posts Give me a day to do some calculations and Riselsieve can also be included in the sieve the program will work as if all of RS's k's were +1. Citrix
 2005-07-07, 04:34 #3 hhh     Jun 2005 373 Posts For everybody who is to lazy to read all the thread, in a few words the facts. SoB has pushed first pass sieve near to 2^50, which is expected to be reached next spring. That's why SoB started a resieving effort with a larger dat, for 991
 2005-07-07, 15:22 #4 VJS     Dec 2004 13×23 Posts I would also like to point out that with the current implementation of proth. A dat size of 53M is the most efficient with respect to time vs work done. 53M is optimal but an odd size number. There is a flat spot in the optimal dat size curve between about 45-55M, any higher than 55M the efficiency drops dramatically. Anything smaller than 45M your out of the optimal size. What this means in a nutshell... Differences between 20M (your dat and SoB's older dat) vs a dat size of 50M. Well 50M dat is 2.5x larger sure... Takes about 50% more memory once you reduce the size (40T). However it is only between 10-20% slower than the 20M dat. So theortically 250% x 85% = ~212% more work done per unit time. Second adding k's isn't that bad on the sieve speed. Doubling the number of k's doesn't half the sieve speed. There is also the issue that by combining k's more mod's will be shared etc... The major problem is that you would have to sieve everything from 20M
 2005-07-07, 18:42 #5 ltd     Apr 2003 77210 Posts I would like to see the merge of ranges if possible. To be honest it would help PSP much more then it would help SOB due to the fact that you have a lot of siever over there compared to our sieve effort at the moment. If you give me time till end of next week i can create a sieve file 1006 to 50Mil. I would push the PSP sieving of the low ranges with all the power i have to have removed as many factors as possible if we decide to merge. Edit: I hope that i can hold the schedule for creating the file. That depends alot on the installation i have to do at a customer site this weekend (friday to monday :( ). If i have to stay there longer then monday evening i think it will take longer as there is lots of work on my desk. Lars Last fiddled with by ltd on 2005-07-07 at 19:08
 2005-07-07, 19:41 #6 VJS     Dec 2004 12B16 Posts You have alot of time to do so, it's more of a think project currently. It will take SoB at least another 6 months if not more to finish secondpass to 100T and first pass to the limit of proth. The major point is getting the dat done, and the first... 3T is a killer ... With a 20M
 2005-07-07, 19:59 #7 VJS     Dec 2004 4538 Posts Alot one more thing... http://www.free-dc.org/forum/showthr...&threadid=8014 This thread is the development of the 991-50M sieve effort, worth a read IMHO since I was one of the people who started it. Some of the earlier post were just plain wrong but I didn't have the data. The graphs will be roughly the same. There is good graph on the second page showing factor density drop off. Around 18T as I had stated earlier. I'd also like to add simply creating the dat and sieving out the first T is a start. Also don't forget to use newpgen or some other program for the first ?? 1G ??? or 64K ??? can't remember. Proth has a minimum value to which it will sieve, 1G though the interface I think 64K if you fudge a pmin= manually. Alot of factors exist below the 1G of course. If you need some advice don't hesitate to ask here, I can tell you only what I know from experience using the client. Last fiddled with by VJS on 2005-07-07 at 20:00
 2005-07-08, 03:03 #8 hhh     Jun 2005 373 Posts As soon as you are ready, PM me and I will give you and email adress that can take the dat or so; I would be pleased to take a chunk. H.
 2005-07-08, 06:24 #9 Citrix     Jun 2003 22·397 Posts Well here is the mathematical calcualtions I did Running time of prothsieve= ***** (sqrt(sum of weight of all k's) + #of k's )* constant * sqrt(range (max-min)) Using this formula the time it would take SOB alone and PSP alone will be 2.4X compared to 1.7 X if PSP and SOB merged. Clearly, it would be better if the 2 project's sieving efforts merged. But if you consider having PSP find all the primes upto 10 million and then sieve upto 50 million the time would be 2.0 X. So it makes sense logically to merge the project's sieving efforts. At the same time it makes alot of sense to merge the rieselsieve and PSP's sieiving effort upto 20M. But the question arises that does PSP want to go to 50M? The answer to this is yes, but with the current computing power it seems almost a fantasy for PSP to reach 50 M in the near future. So, unless more people contribute to the PRP section it will be a waste of computing time for the helpful SOB sievers, Since PSP might never use those sieve ranges (20M to 50M) **** irrespective of whether k's are +1 or -1 constant depends on your machine Hopefully, the above makes sense! Citrix Last fiddled with by Citrix on 2005-07-08 at 06:30
 2005-07-08, 09:32 #10 hhh     Jun 2005 373 Posts Citrix, the above makes sense, I think, but what is your point?, do you want it or not? IMHO, it is true that SoB is behind in sieving, but this is no reason not to help PSP. One project is behind, the other one ahead, no big deal. Anyway, if one day one project is finished, people will probably not retire, but head over for an other. As for rieselsieve, when you look at the discussion on the SoB-site, there seem to be - at least - obstacles. I'm not in the maths, and I have even no idea how the siever works in detail, but these obstacles seem to me (from the discussion), not trivial. If you can solve them, and write a siever that can take rieselsieve into account, I would even opt for taking rieselsieve, too. PSP, SoB, and Riesel would of course be even more efficient. That's BTW why I think we should sit back, think over all these things very well, and then make them good, and once and for all. H.
 2005-07-08, 10:30 #11 thommy   354810 Posts OK, here is a negative thought. PSP is more or less just a fun project. What is so special about a prime sierpinski? Even if it is the lowest. Thats like who was the first afro american on the moon. Its just not important, and most people do not care. SoB seems more worthy for me. What is when the comes a new project testing all k's that are multiples of 15 and 8 mod 25 or whatever just some new k values for form k*2^n+1. Would you like combining that one too in your sieving effort? But i dont sieve anyway, so thats just my opinion.

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