mersenneforum.org sr2sieve- number of candidates in range
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 2013-05-12, 21:37 #1 pepi37     Dec 2011 After milion nines:) 5CF16 Posts sr2sieve- number of candidates in range When I start sr2sieve then program automatically calculates number of candidates that will be removed when sieve process is over. Since it is very usefull info, can someone tell me how sr2sieve calculates that number, what formula can do that computation and give result. Thanks for answer
2013-05-13, 01:30   #2
rogue

"Mark"
Apr 2003
Between here and the

23×809 Posts

Quote:
 Originally Posted by pepi37 When I start sr2sieve then program automatically calculates number of candidates that will be removed when sieve process is over. Since it is very usefull info, can someone tell me how sr2sieve calculates that number, what formula can do that computation and give result.
The number is an approximation.

n*(1-log(p0)/log(p1))

where n is the number of terms and p0/p1 are the sieve limits.

2013-05-13, 09:05   #3
pepi37

Dec 2011
After milion nines:)

148710 Posts

Quote:
 Originally Posted by rogue The number is an approximation. n*(1-log(p0)/log(p1)) where n is the number of terms and p0/p1 are the sieve limits.
Thanks Rogue, but if I look at formula there is no connection with number is sieved and number of candidates.
As we all know, there is some "rich" sieve with many candidates, and there is some very poor sieve with only few candidates left. I know, you say it is approximation, but in whole time I use this program approximation was always very accurate.

 2013-05-13, 12:41 #4 rogue     "Mark" Apr 2003 Between here and the 647210 Posts n is the number of remaining terms in the input range
2013-05-13, 18:56   #5
pepi37

Dec 2011
After milion nines:)

1,487 Posts

Quote:
 Originally Posted by rogue n is the number of remaining terms in the input range
Yes it is ok: but how your formula "know" is sieve rich of factor or ih has very small number of factors ( sieve for K=6883 has only 20 kb and for 2145 has 1200 kb)
Or it is same ratio for all numbers

Last fiddled with by pepi37 on 2013-05-13 at 18:56

2013-05-13, 22:55   #6
rogue

"Mark"
Apr 2003
Between here and the

23·809 Posts

Quote:
 Originally Posted by pepi37 Yes it is ok: but how your formula "know" is sieve rich of factor or ih has very small number of factors ( sieve for K=6883 has only 20 kb and for 2145 has 1200 kb) Or it is same ratio for all numbers
It is the same ratio for all numbers. It is suggested that you sieve to a value like 1e6 (or higher) with srsieve. You can then use the formula to estimate the number of factors.

2013-05-14, 15:11   #7
pepi37

Dec 2011
After milion nines:)

1,487 Posts

Quote:
 Originally Posted by rogue It is the same ratio for all numbers. It is suggested that you sieve to a value like 1e6 (or higher) with srsieve. You can then use the formula to estimate the number of factors.

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