P-1 B1/B2 selection with "Test=" vs "Pfactor="

James Heinrich · 2005-03-19, 20:55

Why is it that the B1/B2 bounds selected are so vastly different with the same exponent on the same machine if the P-1 test is invoked with these two different lines?

Code:

Pfactor=79299821,72,1

Test=79299821,72

The Pfactor line gives

Quote:

B1=395000,B2=8295000, chance = 3.84%

The Test line gives

Quote:

B1=835000,B2=21918750, chance = 5.13%

Why would Prime95 select such vastly-different bounds for the two testing methods? Whether a LL is going to be performed immediately afterwards shouldn't make any difference... should it?

garo · 2005-03-19, 21:32

Try

Pfactor=79299821,72,0

The answer lies in whether a factor would save one test or two.

James Heinrich · 2005-03-19, 21:58

Indeed...
Pfactor=79299821,72,0 gives the same result as Test=79299821,72

Now I better understand the documentation:

Quote:

Pfactor=exponent,how_far_factored,has_been_LL_tested_once

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
GQQ: a "deterministic" "primality" test in O(ln n)^2	Chair Zhuang	Miscellaneous Math	21	2018-03-26 22:33
Stockfish game: "Move 8 poll", not "move 3.14159 discussion"	MooMoo2	Other Chess Games	5	2016-10-22 01:55
Aouessare-El Haddouchi-Essaaidi "test": "if Mp has no factor, it is prime!"	wildrabbitt	Miscellaneous Math	11	2015-03-06 08:17
Would Minimizing "iterations between results file" may reveal "is not prime" earlier?	nitai1999	Software	7	2004-08-26 18:12

2005-03-19, 21:32	#2
garo Aug 2002 Termonfeckin, IE 2⁴×173 Posts	Try Pfactor=79299821,72,0 The answer lies in whether a factor would save one test or two.