20081031, 10:14  #1 
"Nathan"
Jul 2008
Maryland, USA
5·223 Posts 
Recommended TF bit levels for M(>10^8)
Hi,
Wondering if anyone knows around what bit level we should TF up to for LMHsized numbers. I think I remember seeing something like 2^72 for numbers around M100,000,000, but I'm thinking about even bigger numbers  for instance, I was looking at numbers around M867530900 ("Jenny numbers"!)  it seems like it might be wise to go almost up to 80 bits here? I recently also worked on M999999937 (biggest number PrimeNet lists), factoring up to 2^73  that took the better part of 24 hours, but considering that the LL test timed out to almost 70 years, I guess it's worthwhile to go much higher. Where should we start P1'ing numbers this huge? 
20081031, 11:23  #2 
"Jacob"
Sep 2006
Brussels, Belgium
2^{2}×439 Posts 
The values I have (from the sources of v24 and v25) are :
Code:
Bits up to Exponent 56 1 000 000 57 1 480 000 58 1 930 000 59 2 360 000 60 2 950 000 61 3 960 000 62 5 160 000 63 6 515 000 64 8 250 000 65 13 380 000 66 23 390 000 67 29 690 000 68 37 800 000 69 47 450 000 70 58 520 000 71 75 670 000 72 96 830 000 73 115 300 000 74 147 500 000 75 186 400 000 76 227 300 000 77 264 600 000 78 337 400 000 79 420 400 000 80 516 000 000 Code:
#define FAC80 516000000L #define FAC79 420400000L #define FAC78 337400000L #define FAC77 264600000L #define FAC76 227300000L #define FAC75 186400000L #define FAC74 147500000L #define FAC73 115300000L #define FAC72 96830000L #define FAC71 75670000L #define FAC70 58520000L #define FAC69 47450000L #define FAC68 37800000L #define FAC67 29690000L #define FAC66 23390000L /* These breakevens we're calculated a long time ago on unknown hardware: */ #define FAC65 13380000L #define FAC64 8250000L #define FAC63 6515000L #define FAC62 5160000L #define FAC61 3960000L #define FAC60 2950000L #define FAC59 2360000L #define FAC58 1930000L #define FAC57 1480000L #define FAC56 1000000L Jacob 
20081031, 11:50  #3 
"Nathan"
Jul 2008
Maryland, USA
2133_{8} Posts 
That's just what I was looking for
Thanks, Jacob. This should almost be made into a sticky, at least in the LMH forum. It makes sense that there's no information about numbers over M5xx,000,000; I believe the current version of Prime95 will not do an LL test over M596,000,000.
You really gain an appreciation for just how expensive LL testing on these kinds of numbers is when you consider that weeks, or even *months* of trial factoring makes good sense. Like on M999,999,937, I took a day to get to 73, so it would be roughly 2+4+8+16+32+64+128+256 = 510 days, or just under 1 1/2 *YEARS* :surprised just on trial factoring to 81 bits (and I bet M999,999,937 ought to go out to 84 or 85 bits, really). Wow. Then again 1 1/2 years factoring is just a brief prelude to the 7080 year LL test my computer estimated for M999,999,937. I think I'll stick with my 30M exponents for now. Thanks again for the info! 
20081101, 03:35  #4 
Dec 2003
Hopefully Near M48
6DE_{16} Posts 

20081101, 04:10  #5 
6809 > 6502
"""""""""""""""""""
Aug 2003
101×103 Posts
53·191 Posts 
Last fiddled with by garo on 20081101 at 08:02 Reason: removed link due to a virus warning. Are you sure Batalov? 
20081101, 07:40  #6 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
9,623 Posts 
This page is virusinfected, did you know that?

20081101, 09:10  #7 
Dec 2003
Hopefully Near M48
2·3·293 Posts 
Funny. Prime95 v24.14 at least doesn't seem to give estimates beyond 30 years (it just says estimated completion time after 2038).

20081101, 09:32  #8 
"Nathan"
Jul 2008
Maryland, USA
5×223 Posts 
LL testing time
I should have elaborated on how I got 7080 years. I used the Advanced > Time option in Prime95 v25.7 to run several 1000 iteration tests of M999,999,937. From the average iteration time, I extrapolated out to 999,999,937 iterations requiring somewhere between 70 and 80 years.
You're right that Prime95 will not display completion times beyond 2038 (actually, beyond whatever second marks the Unix time rollover  2,147,483,647 seconds after midnight on January 1, 1970  hint: what's the largest value that'll fit in a 32bit integer?). If you look in prime.ini (I think), you'll see references to estimated completion times given in Unix time. WRT the link, I actually went there and watched the video, and didn't get virusized. Hope there's not now something going on in my computer that I'm not aware of... 
20081101, 12:38  #9 
Banned
"Luigi"
Aug 2002
Team Italia
4834_{10} Posts 

20081101, 12:46  #10  
Undefined
"The unspeakable one"
Jun 2006
My evil lair
6302_{10} Posts 
Quote:
Last fiddled with by retina on 20081101 at 12:46 

20081101, 17:04  #11 
6809 > 6502
"""""""""""""""""""
Aug 2003
101×103 Posts
53×191 Posts 
I didn't until later. The problem did crop up for me until about 10 pages in, on that site. Thanks Garo. I don't want to be the cause of a problem.
Last fiddled with by Uncwilly on 20081101 at 17:25 
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