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Old 2009-06-12, 05:13   #1
cipher
 
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Default Improving Sieving by 18%.

I decided to help with PSP sieving. http://www.mersenneforum.org/showthread.php?t=2666

when i downloaded the sieve file "Sievecomb" or Sob.dat i realized that the n values have not been truancted, hence i truncated n from n=1 to n=6mil as all the k's have been PRP'd upto n=6mil min. The resulting file was 14% lighter and 18% faster with sr2sieve.

So here it is the new sieve file (unofficial) where n=6mil to 50mil, for all the K's. (The file is RAR'd use winrar or winzip to unzip the file.)
http://www.sendspace.com/file/iwjqzl

Now when you start sr2sieve you have to make one small change. On your command prompt.
Code:
Before: Example
sr2sieve -s -p 70115500e9 -P 70123500e9
Now:
sr2sieve -i sr_2.abcd -p 70115500e9 -P 70123500e9
Everything else stays the same and you get same results.

Thanks
Cipher
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Old 2009-06-12, 05:30   #2
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I have not tried your file so far but there is at lesast one problem with it. The lower bound for sieving PSP is at 1.5M !!! As our second pass testing for all k has only reached the 1.5M level all factors above that are still very important.
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Old 2009-06-15, 14:00   #3
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Yes we have contimplated this before...

reducing to 6M is actually too much at a max the reducion would be 1.5M as lars said.

Please remove your file

Second the calculated increase should be

[(41^6)/(50^6)]^0.5 = which is about 9% not 18%, which is a little weird. I think you might have removed a little too much.

Also if the efficiency were really that different we should crop the top end. Bring it back to say 1.5M<n<30-40M. But with all the effort we introduced shrinking to top end is not a good idea, we would probably never go back on do the 40-50M we missed.
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Old 2009-06-16, 09:03   #4
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As an information about the next steps.
I have at home the most recend dat files (all known factors removed) in a form starting at 991 and also starting at 1.5M. I will start a testrun under identical conditions to see the real speed changes.
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Old 2009-06-16, 10:34   #5
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Quote:
Originally Posted by ltd View Post
As an information about the next steps.
I have at home the most recend dat files (all known factors removed) in a form starting at 991 and also starting at 1.5M. I will start a testrun under identical conditions to see the real speed changes.
I'm looking forward to hearing the results.

Also, I'm planning on finding a prime this summer... Will that help?
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Old 2009-06-16, 15:51   #6
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Quote:
Originally Posted by opyrt View Post
I'm looking forward to hearing the results.

Also, I'm planning on finding a prime this summer... Will that help?
Finding a prime is the best thing that you can do!

Finding two primes would be even better!.
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Old 2009-06-16, 20:05   #7
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Quote:
Originally Posted by Joe O View Post
Finding a prime is the best thing that you can do!

Finding two primes would be even better!.
Stop slacking and get to it.
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Old 2009-06-16, 21:21   #8
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Quote:
Originally Posted by Sloth View Post
Stop slacking and get to it.
Oh, sorry! I'll get to it straight away! I'll just copy what you did, and we should have them any time soon!
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Old 2009-06-17, 03:12   #9
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Joe and I spent god only know how many weeks and CPU hours perfecting that dat at 991<n<50M and found that a 4#M dat was most efficient???

Joe, perhaps you can remember and elaborate but the selection of a 50M dat was not hap-hazard. The discussion of if it should be shortened or lengthend is for another debate...


Lars speed test would be a good one to start with, when Joe and I did it we used the old sieve client that predated JJsieve ( a significant speed improvement ). Perhaps the sieve speed is more directly related to n-range but I doubt it.

In any case please continue with the current offical dat, the mess of not using it takes more CPU hours an manpower to clean up than one might expect. And certainly more than the user would save.

I appologize for not having more time to invest in the testing, I'm working around 60 hours a week right now.
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Old 2009-06-18, 14:52   #10
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The testrun has finished. The gain was even smaller then expected.
The file with n>1.5M needed 151354 seconds
The file with n=991 needed 152360 seconds.
This would mean there is a gain of 0.66% by changing to a shorter file.
I expect that there is a possible error of around +/-0.2% due to the fact that the machine was in normal use for 3hours during the test.
So the expected gain would be between ~0.45% and ~0.85%.

Last fiddled with by ltd on 2009-06-18 at 14:52
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Old 2009-07-01, 13:34   #11
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Please forgive me what I write here is totally moronic, but aren't all factors interresting with regards to having more complete data as to what candidates are not primes? LLR tests only say "this is not prime", while sieving says "this candidate is divisible by that factor and is not prime", right?

In my mind, this is a good reason not to cut down the sieve span.
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