20230919, 23:40  #12  
Jun 2010
100010000_{2} Posts 
Quote:


20230920, 00:10  #13 
Random Account
Aug 2009
Oceanus Procellarum
2^{2}×5×151 Posts 

20230920, 03:18  #14  
"Gary"
May 2007
Overland Park, KS
11000100000100_{2} Posts 
Quote:
n=1.7M seemed like a good choice based on where it feel on the FFT and no one had any notions that they would get top5000 primes from it. I don't know why a change is being considered. If any change is done, I would suggest running the remainder of PrimeGrid's n=1.29M file when they shut their effort down. That would give a reasonable chance at a #1 twin. I'll go further and say that we should replace our port 13000 work for n=3.322M with the n=1.29M effort. Last fiddled with by gd_barnes on 20230920 at 03:21 

20230920, 03:46  #15  
Jun 2010
2^{4}·17 Posts 
Quote:


20230920, 04:26  #16  
"Michael Kwok"
Mar 2006
1,213 Posts 
Quote:
For n=1950000, the graph and timings I posted do show an efficiency gain over n=1700000, but the effect is quite small. On a core i7 7700K, n=1.95M tests will take ~1115 seconds to complete, vs. ~947 seconds to complete for n=1.7M. Quote:
Quote:


20230920, 04:31  #17  
"Gary"
May 2007
Overland Park, KS
2^{2}·3,137 Posts 
Quote:
Why deviate from the n=1.7M search for top5000 primes that will only be there for a few months? It takes n=1.833M to make the top5000 now. What would be the point of n=1.95M? The bottom of the list would likely be near ~1.9M before we started. You may as well have stayed at n=1.7M at that point. And if you go to n=2.58M, you have next to zero chance of twin. If anything, we could consider replacing the n=3.322M tests with 1.95M/2.58M. The idea being that this is a twin search, not a top5000 search. Otherwise we are continuously chasing the top5000 list. Last fiddled with by gd_barnes on 20230920 at 04:33 

20230920, 12:04  #18 
"Alexander"
Nov 2008
The Alamo City
2×7×73 Posts 
PrimeGrid has already mentioned that a reboot of their Sophie project at a larger n is a possibility. If so, there is no point in doing work at these larger n's, as PrimeGrid would likely test (or surpass) them anyway. Chasing the top 5000 is pointless, as it would require constantly sieving new n's and ditching old ones as soon as they fall below the threshold (likely before the files are done).
This is the Twin Prime Search. We aim to find (large) twin primes, with Sophie Germain primes as a side effect. Any project decisions should be made with the goal of finding twin and Sophie Germain primes as the primary objective. 
20230920, 15:00  #19  
Dec 2010
44_{10} Posts 
Quote:
"With a decently wellcoded set of nonpowerof2 FFTpass routines this effect should be on the 5%penaltyorless ballpark, when normalized by FFT length. If you see a timing effect much larger than that it's usually due to cachemapping issues or quirks of the multithreading, both of which can be difficult to track down." Finding a twin or Sophie at n=1.95M requires 55% more work than finding one at n=1.7M even after those efficiency gains are included: (1115/947)*(1.95/1.7)*(1.95/1.7) = 1.549 I'm in favor of sticking with n=1.7M. There's already n=3.322M at port 13000 for those who want a prime in the top 5000. On a related note, will there be any additional sieving done on either n=1.7M or n=3.322M beyond the current p=1047T / p=1130T limits? 

20230921, 20:51  #20 
"Norman Luhn"
Jan 2007
Germany
2×5×7×11 Posts 
Don't want to out myself now...
Has anyone ever had the idea to pick out an area after intiution where a twin could be, without systematically searching everything. I have the ability to do that. That can save years ! Last fiddled with by Cybertronic on 20230921 at 20:51 
20230922, 04:08  #21 
Dec 2010
54_{8} Posts 

20230922, 07:39  #22 
"Michael Kwok"
Mar 2006
1,213 Posts 

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