mersenneforum.org > Data Useless p-1 work
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2004-11-26, 19:16   #1
jocelynl

Sep 2002

2×131 Posts
Useless p-1 work

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

2004-11-26, 20:55   #2
xilman
Bamboozled!

May 2003
Down not across

23·1,249 Posts

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

 2004-11-26, 21:21 #3 jocelynl   Sep 2002 4068 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
2004-11-28, 13:21   #4

"Richard B. Woods"
Aug 2002
Wisconsin USA

769210 Posts

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

 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

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