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Old 2007-12-11, 03:51   #49
gd_barnes
 
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May 2007
Kansas; USA

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Quote:
Originally Posted by kar_bon View Post
something like this:

call:
pfgw -tc -q"1468*11^26258+1"

output:
PFGW Version 20031222.Win_Dev (Beta 'caveat utilitor') [FFT v22.13 w/P4]

Primality testing 1468*11^26258+1 [N-1/N+1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 2
Running N-1 test using base 3
Running N+1 test using discriminant 23, base 1+sqrt(23)
Calling N-1 BLS with factored part 100.00% and helper 0.02% (300.02% proof)
1468*11^26258+1 is prime! (813.9536s+0.1133s)

karsten
Hi Karsten,

Thanks for the feedback. I tried Axn1/Rogue's suggestion of using the -tm switch along with the -f0 switch and it speeded up the search on your prime by nearly 10 times!! Apparently the -f0 switch causes it to not do any trial factoring, which would certainly be unneccesary for a probable prime. -tc apparently does both a +1 and -1 test so it also does more testing than is needed. -tm does just what you need here...it only does a -1 test, which is what is needed for a +1 probable prime. Here is the output:

Primality testing 1468*11^26258+1 [N-1, Brillhart-Lehmer-Selfridge]
Running N-1 test using base 2
Calling Brillhart-Lehmer-Selfridge with factored part 99.99%
1468*11^26258+1 is prime! (83.0808s+0.0065s)

The input to PFGW was: "pfgw -tm -f0 -q1468*11^26258+1"

Particulars of the test:

It was run on a 1.66 Ghz Dell Core duo laptop. (It seems to run about as fast as a 3 Ghz P4.)

My version of PFGW does not accept the quotes around the equation.

Per the README file, I am using PFGW v1.2 Release (January 30, 2005). I downloaded it 2-3 months ago.


I hope this saves you a little time too! It did me...I needed to test a much larger prime for base 17 that took almost 6 times as long as the one you tested, i.e. 92*17^51311+1, which took 476.1328s+0.0087s.

Thanks Rogue, Axn1, and Karsten for helping!


Gary
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