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Old 2016-12-17, 02:04   #1
carpetpool
 
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"Sam"
Nov 2016

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Post Sieving in PFGW

Using PFGW's nextprime (or previousprime) with input.txt function, does adding

pfgw -f -e10000 input.txt

sieve values with small factors, and not prp test them. (In other words, does this save a lot of time from what this would normally take?) Also, I remember reading in pfgwdoc.txt that there is a sieve option (included in the ABC and ABC2 files) that trial divides numbers, and if a factor is found will not prp test that number, if no factor is found, a PRP test will begin. The PRPs are reported to pfgw.log as usual. Does anyone know the pfgw command-line switches for this? Thanks for helping me figure out a sieve with pfgw.
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Old 2016-12-17, 03:38   #2
rogue
 
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Quote:
Originally Posted by carpetpool View Post
Using PFGW's nextprime (or previousprime) with input.txt function, does adding

pfgw -f -e10000 input.txt

sieve values with small factors, and not prp test them. (In other words, does this save a lot of time from what this would normally take?) Also, I remember reading in pfgwdoc.txt that there is a sieve option (included in the ABC and ABC2 files) that trial divides numbers, and if a factor is found will not prp test that number, if no factor is found, a PRP test will begin. The PRPs are reported to pfgw.log as usual. Does anyone know the pfgw command-line switches for this? Thanks for helping me figure out a sieve with pfgw.
Use the -f option. pfgw only does trial factoring. It does not sieve. If a trial factor is found, it will not PRP test the number.

You are always better off using a sieve, even if you have to write one.
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Old 2016-12-17, 07:58   #3
carpetpool
 
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Although I am a beginner at finding primes, I only know sieving programs which work with sieving the range n, n+k to a certain depth. I do not know of a program which works with sieving numbers of the form pk+s, with the range p = n to n+k. Please let me know if you know of one.

Edit: I don't know if Newpgen counts, that is for numbers of the form k.b^n+-1, not for sieving numbers of the progression pk+s to a certain depth.

Last fiddled with by carpetpool on 2016-12-17 at 08:00
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Old 2016-12-17, 14:55   #4
rogue
 
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Quote:
Originally Posted by carpetpool View Post
Although I am a beginner at finding primes, I only know sieving programs which work with sieving the range n, n+k to a certain depth. I do not know of a program which works with sieving numbers of the form pk+s, with the range p = n to n+k. Please let me know if you know of one.

Edit: I don't know if Newpgen counts, that is for numbers of the form k.b^n+-1, not for sieving numbers of the progression pk+s to a certain depth.
I can't think of any program, but one might exist. I you know anything about writing software, it might be possible to take someone else's code and make it sieve this form for you. If you don't, I highly suggest that you learn C and some x86 assembly.
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