20080621, 12:20  #1  
Jan 2006
Hungary
2^{2}·67 Posts 
Discussion about CPU time needed and k's remaining
Quote:
Willem. 

20080621, 15:19  #2  
Quasi Admin Thing
May 2005
1111010000_{2} Posts 
Quote:
Does anyone know, is it possible to use sr2sieve to sieve different bases? and is it possible to use sr2sieve to sieve both Riesels and Sierpinskis? If it is, I really think that even better sieving could be carried out 

20080624, 07:18  #3  
May 2007
Kansas; USA
2×41×131 Posts 
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This is likely to be 2550 CPU years (or more) of work and you'd probably want to have 1020 total quads dedicated to prime searching in order to complete it in a semireasonable timeframe...half of them or more to work on this and the other half for other efforts to keep things interesting. Remember that these are bases 22 and 23 not base 3. Base 3 is a very prime base and the tests are much smaller for the same nvalue. I could perhaps see attacking 10 k's on base 3 to n=1M on a single quad (or 6 cores) but that would also likely be several CPU years of work and could still take up to a year on a single quad, depending on how lucky you were to find primes early on. It's OK if you want to sieve n=100K1M. That's a very good idea and it helps the project greatly. I just want you to be aware of the boredom factor when LLRing (or PFGWing or Phroting or whatever software you use), which will set in very quickly on these bases especially as you push past n=200K250K on all kvalues remaining. Thanks, Gary 

20080627, 05:46  #4  
May 2007
Kansas; USA
2·41·131 Posts 
Quote:
Completing the Sierp base 19 run on just 2 cores to n=100K will likely take 6 months to a year or more with 1539 k's remaining at n=11.12K. Can you give an update on that effort before getting too much into the base 22 and 23 effort? Thanks, Gary Last fiddled with by gd_barnes on 20080627 at 05:50 

20080628, 05:37  #5  
Quasi Admin Thing
May 2005
2^{4}·61 Posts 
Quote:
Regarding base 22 and 23, sieving is also really greatly progressing. At the moment you can decide what kind of reservation you would make for me. At least for the next 4 weeks or so, sieving will be the only work done at these Bases. This is the sieve status on the bases: Riesel Base 22: Sieved to 2645779448941 and less than 34527 k's remain Riesel Base 23: Sieved to 2841008935111 and less than 29079 k's remain Sierpinski Base 22: Sieved to 1721884962157 and less than 59047 k's remain Sierpinski Base 23: Sieved to 2944135041649 and less than 26058 k's remain Iteration timing: Must wait... but will come So let me know, what kind of reservation you would like for me to do, sieve/LLR vice? It's fine with me to do just sieving, though it actually makes this kind of prime searching more boring if one only gets to look for factors and never gets the chance to look for primes KEP! 

20080628, 06:54  #6 
Quasi Admin Thing
May 2005
1720_{8} Posts 
@ Gary:
I've given my reservations some thoughts, and here is what I've decided: I'll sieve for 1 week more on all my Base 22 and Base 23 reservations. Maybe 2 weeks if I have to work in the next weekend. After that I will see if I can complete the verification process of the k<250M for Base 3. The sieve files will be 4, and maybe somone can merge them among different bases and/or Riesel and Sierpinski combined, so it actually works If I'm going home for the next weekend (living 2 places, thats what actually makes it difficult to give feedback), then I will put all 4 cores from the quad working on the base 19. Hopefully this will bring it much faster down and closer to 0 k's. Now let me hear what you say Gary... maybe a sieve drive before LLRnet should be considered, especially since I may consider to do some more work on these bases once I wrap the base 19, but that holds for the future to see Take care everyone. KEP Ps. Sieve speed for the Riesel Bases is ~5,000,000 p/sec. For sierpinski base 22 sieve speed is ~3,000,000 p/sec and for Sierpinski base 23 sieve speed is ~5,200,000 p/sec. Last fiddled with by KEP on 20080628 at 06:56 Reason: Just added some sievespeed measurements 
20080628, 09:28  #7 
May 2007
Kansas; USA
2·41·131 Posts 
KEP,
Thanks for the response. I had noted in your last status for Riesel base 3 that you were taking it to k=500M. I'll change in now to k=250M. No, I'm not encouraging you to only sieve. Few people would find only sieving interesting. I currently have you reserved for the following: Riesel base 3 to k=250M and n=25K. (A big amount of work) Sierp base 19 to n=100K for all 1500+ kvalues remaining. (A huge amount of work) Riesel and Sierp bases 22 and 23 to n=1M for all 10 k's remaining. (An astromically enormous amount of work) I can't dictate what people reserve. I can only attempt to keep efforts moving if possible. I can ask that they continue working on things that they reserve or unreserve part of their reservation if they determine that they reserved too much or if they are no longer interested in them, which you have done. I can also remind them of the amount of work that they are reserving. That's what I'm reminding you about here. If I were to make a recommendation for these 6 bases for 6 highspeed cores and you would like to do plenty of sieving AND primality testing, I would suggest this: Keep your Riesel base 3 reservation as is and put 2 cores on it nonstop if possible. This will likely take 48 weeks. Reduce your reservation on Sierp base 19 to n=30K or 35K. I know this seems small but I promise you it will be much more work than you may realize for 1500+ k's for a base that isn't very prime. Initially put 2 cores on it and sieve and LLR as you go as needed. When Riesel base 3 is complete, put its 2 cores on this to get it completed quickly. This would take perhaps 23 months by adding the extra 2 cores after 48 weeks. Reduce your reservation on Riesel and Sierp bases 22 and 23 to n=250K. Initially have 2 cores on it for sieving and then LLRing as needed. When Sierp base 19 is complete, move all 4 cores over to it for a total of 6. This will still be a very large amount of work. I have no idea how long this will take. I will speculate 48 months by adding the extra 4 cores after 23 months. It all depends on how quickly the 10 k's drop but I will guess that they will be very slow to drop. Reference bases 22 and 23, on my reservation for Sierp base 12 using your sieved file, it has taken me 10 days to process n=129K160K on one highspeed core but it is slowing greatly. My estimated time to n=250K (the limit of your sieved file) on one core is ~3 months. Tests at n=160K are coming in at 2200 secs. or about 37 mins.! Extrapolating without an actual test, I can say that it will take 900010000 secs. or 2.53 hours per test at n=250K!! And that's only base 12! In suggesting this, I'm not saying that you should reduce the range of what you are sieving. Many people, Jean Penne is our main one, sieve much larger ranges then they intend to test to help out the effort. When complete with Sierp base 19, leave your n=30K or 35K to 100K file for the team and when complete with Riesel and Sierp bases 22 and 23, leave your n=250K1M file for the team. Even when you complete the above, I'm sure a large portion if not all of them will still be available and besides, you may find a more interesting effort at that point. Gary Last fiddled with by gd_barnes on 20080628 at 09:34 
20080628, 09:55  #8 
Quasi Admin Thing
May 2005
2^{4}·61 Posts 
@Gary:
First a timing for k=68 n=999991 for sierpinski base 23: ~44 ms or 199,035.232 seconds per test. So at now a maximum completion time of: 31,447,566,656 seconds. However sieving is moving 9 k's an hour per core still, so huge amount of work is still saved by doing sieving. However here is some comments to your plan (which I really liked and may stick to): 1. Keep my reserved range for Riesel Base 3 for k<=500M, since it has been PRP tested to n<=500 and verification of the PRPs will start monday on both the 250M k ranges and sieving of the Base 19 will be haulted for now. 2. Next friday I will bring all my 4 cores on the quad working on each ~385 k's. This will mean that by next friday I'll stop sieving on the bases 22 and 23. With the current speed more than a thousand candidates should be factored. 3. In 46 weeks at least the Base 19 should be completed to n<=100K and hopefully the Base 3 Riesel will have been completed to n<=25K, so at this time I should be able to put six cores working on these 4 bases. When that happens I plan to sieve a great deal further (hopefully to 25T) which is about 10 weeks of sieving time. After that I intend to split the sieved files up in pieces which can keep my 6 cores run individually for 6 weeks without running dry. The above plan I hope to see greatly progressed around christmas, and if any of the base 22 and base 23 k's should remain, I figure that about that time the k/n pairs has gotten so high that further sieving might be nescessary for the remaining k's before a public release... Anyway hope this is not to long an outcast, and looks forward to be able to send you a lot of primes every week untill the Base 19 is completed. Also I hope that it is OK with you if I keep my reservations for now. Maybe later on if the task of running the bases 22 and 23 gets to scary or turns out to be to hard to complete, of course we can then discuss a public release. Also sorry if I sounded agrevated, but I really believed that I could get somewhere and I also thinks if I put 46 cores on sieving the high bases, no problems with getting somewhere will in fact be seen Take care my friend! Kenneth! 
20080628, 15:30  #9 
Jan 2005
479_{10} Posts 
As for an idea how long it all takes:
Riesel base 31, there are 9 k's left. On 1 core, it took 2 months (minus 2 days) to go from n=68133 to 78661! I haven't checked whether I'll be hitting another FFTswitchover, but if so, timings will be much worse after that happens. If nothing interesting happens (primes :)) I'll have about 5 months of work only for 9 k's to only 100k! and... 31,447,566,656 seconds is about 1000 CPUyears...!! (ok... that is the MAX time :) ) anyways, I hope you can turn up your muscles and get it done with :) (Finding primes early on will most certainly help a lot!) Last fiddled with by michaf on 20080628 at 15:31 
20080628, 16:12  #10  
Quasi Admin Thing
May 2005
1111010000_{2} Posts 
Quote:
Thank you! KEP 

20080628, 20:57  #11  
May 2007
Kansas; USA
2·41·131 Posts 
Quote:
On sieving, you're mistaking the elimination of candidates as substantially reducing the overall testing time of the entire nrange. It does not if you're sieving optimally because when estimating, you have to account for sieving and LLRing time. It only saves time at the nranges in which LLRing takes longer than the removal rate of your sieving. If you're sieving optimally, the sieving removal rate SHOULD be slower than the lower nrange testing level and faster than the higher nrange testing level. That is for n=100K, your testing time might be 1800 secs. but your optimal removal rate might be 3500 secs. for the range of n=100K200K because you need to sieve until the removal rate is the same of an LLRtest at 70% of the nrange that you are breaking off for primality testing (would be n=170K for n=100K200K). I may have stated this before but the optimal thing to do in sieving is to sieve until the removal rate is about the same as the primality testing time at 70% of the nrange but break off sieving pieces in powers of 2 nranges for primality testing. So for n=100K1M, you'll LLR a candidate at n=170K to get a testing time, break off n=100K200K from sieving for primality testing when the sieve rate is about the testing time, then LLR a candidate at n=340K to get a testing time, break off n=200K400K when the sieve rate is about that testing time, LLR a candidate at n=680K, break off n=400K800K when the sieve rate is about that testing time, LLR a candidate at n=940K, and finally sieve n=800K1M until the sieve rate is about that testing time. In other words, you don't continue to sieve the entire nrange the whole time. Technically, the more pieces you break off, the more efficient it is CPUwise. It's just a matter of how much you want to mess with it. But the efficiency begins to drops greatly if you don't break it off at least in powers of 2 nranges. By powers of 2, I mean your lower candidate (100K in this case) times 2^q. It sounds like you'll be reducing your reservation at some point on the bases 22 and 23 and providing a sieved file for the team for the nranges above that which you test. Great! At n=~1M on base 23, that's over 2 days to test! One more thing that I'll add on that: I would be surprised if we found primes for more than 6 out of the 10 k's remaining on those bases to n=1M! It might only be 35 of them. These high bases and nranges on bases that are not very prime are TOUGH to find primes for! Many of these conjectures I do not expect to be proven in our lifetimes! (believe it!) :) I have a suggestion for you to get a better rough estimate of the time it will take to LLR Sierp base 19. Find a candidate that is at about 60% of your nrange. So for n=10K100K, that would be n=64K. Then LLR that candidate. Now multiple that time by the total number of candidates you have remaining in your sieved file. THAT should be close to the total time it will take you to LLR the entire nrange. Of course we can probably reduce that by 1020% because kvalues can be removed as primes are found. Also, of course further sieving reduces that LLRing time but you're taking time to sieve also. If you sieve in the optimal manner above, you should get close to the most efficient combination of sieving and LLRing. If you want to LLR an n=64K candidate and provide me with the time it takes and also let me know the number of candidates remaining in your n=10K100K (or n=11.2K100K or whatever) sieved file, then perhaps I can give you a better idea of how to estimate the level of resources needed or how long it will take with your current allocated resources to complete Sierp base 19 to n=100K. At that point, we might be able to get a good idea of how high you'd like to take bases 19, 22, and 23. Gary Last fiddled with by gd_barnes on 20080628 at 21:06 

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