Useless p-1 work

jocelynl · 2004-11-26, 19:16

Quote:

77900201,825000,22893750
77900461,825000,22893750
77900497,825000,22893750
77909939,825000,22893750
79279351,825000,15881250
79299397,780000,11700000
79299421,725000,7612500
79299433,660000,3465000
79299719,780000,12480000
79299821,1110000,1110000
79299907,1110000,1110000
79299959,740000,16465000

What a waste of cpu cycles!
all b1's are smaller than m so they assume that the largest factor of p-1 is m and they don't reach it.

what a waste!

Joss

xilman · 2004-11-26, 20:55

Quote:

Originally Posted by jocelynl

What a waste of cpu cycles!
all b1's are smaller than m so they assume that the largest factor of p-1 is m and they don't reach it.

what a waste!

Joss

Be careful! George's code includes an additional m over and above the ones implied by the b1 limit. I asked him this very question some time ago.

Paul

jocelynl · 2004-11-26, 21:21

So I see!

I tested 2^251-1
b1=2 b2=2 and found the factor 27271151

Tks xilman
You're right, b1 is actually b1+m
There was no wasted cycle.
I pushed the

too early.

Joss

cheesehead · 2004-11-28, 13:21

Quote:

b1 is actually b1+m

No. Prime95 enforces minimum values on b1 and b2, so b1 = b2 = 2 got bumped up. The minimum used to be 30; maybe now it's 60 or more.

27271151 - 1 = 2 × 5^2 × 41 × 53 × 251

cheesehead · 2004-11-28, 13:28

Pminus1=79299433,660000,3465000,0,0

This will find any factor of 2^79299433-1 where

factor = 2 * k * 79299433 + 1

and

k has largest factor =< 3465000 and all other factors =< 660000.

Actually, there are stage 2 extensions such that some k with largest factor =< (3465000 * a small integer) will be found, in certain cases.

2004-11-28, 13:28	#5
cheesehead "Richard B. Woods" Aug 2002 Wisconsin USA 2²·3·641 Posts	Pminus1=79299433,660000,3465000,0,0 This will find any factor of 2^79299433-1 where factor = 2 * k * 79299433 + 1 and k has largest factor =< 3465000 and all other factors =< 660000. Actually, there are stage 2 extensions such that some k with largest factor =< (3465000 * a small integer) will be found, in certain cases. Last fiddled with by cheesehead on 2004-11-28 at 13:31

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Posts that seem less than useless, or something like that	jasong	Forum Feedback	1054	2022-06-20 22:34
Fedora gedit for bash has become useless	EdH	Linux	11	2016-05-13 15:36
Useless SSE instructions	__HRB__	Programming	41	2012-07-07 17:43
Useless DC assignment	lycorn	PrimeNet	16	2009-09-08 18:16

2004-11-26, 21:21	#3
jocelynl Sep 2002 106₁₆ Posts	So I see! I tested 2^251-1 b1=2 b2=2 and found the factor 27271151 Tks xilman You're right, b1 is actually b1+m There was no wasted cycle. I pushed the too early. Joss