20100418, 01:13  #1 
Apr 2010
27_{10} Posts 
How much Trial Factoring to do?
Hello All,
I've been assigned some exponents in the 50M range to be LL tested. They were Trial factored up to 2^68 and P1 factored and not factors found. Would it make sense to manually assign the exponent to be Trial factored up to 2^70 just to make sure it does not have any low factors and then LL test it if it does not? It takes about 18 hours to Trial factor one increment like from 2^68 to 2^69 so 36 hours to go from 2^68 to 2^70 and it takes 25 days to LL test. Please tell me if this would be a waste of time. Thanks! Last fiddled with by odin on 20100418 at 01:17 
20100418, 02:46  #2 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
1000010101011_{2} Posts 
If you use the default configuration, (e.g. you use Test= and don't modify the TF'd depth, etc.) Prime95 will automatically choose what should optimally be done. According to http://mersennearies.sili.net/facto...tton=Calculate, for an exponent size 50M, Prime95 will factor to 2^69.
Last fiddled with by MiniGeek on 20100418 at 02:47 
20100418, 02:47  #3 
"Mark"
Feb 2003
Sydney
3·191 Posts 
Hi Odin,
Assignments in the 50M range should be trial factored to 2^69 before the LL test, unless the bounds have changed since version 24.12. George worked out that's optimum in terms of work done overall. The way it's supposed to happen is: TF to 2^68, P1, TF to 2^69, LL. I thought the client (mprime or prime95) automatically did any missing factoring steps before the LL, so you shouldn't need to do anything manually. Has your LL test started? (MiniGeek beat me to it!) Last fiddled with by markr on 20100418 at 02:48 
20100418, 05:38  #4  
Oct 2007
Manchester, UK
17·79 Posts 
Quote:
Each bit increase represents a DOUBLING of the work done in the previous level. To put it another way, it would take the same amount of CPU time to trial factor from scratch to 69, as it would to trial factor from 69 to 70. 

20100808, 20:23  #5  
Sep 2006
The Netherlands
704_{10} Posts 
Quote:
Todays hardware is far faster in floating point and relative slower in trial factoring, so the break even points are not so accurate anymore. "slower" i mean: the intels are ugly slow in trial factoring versus the AMD's very fast, yet in floating point both intel as well as todays AMD's are real fast for the LL. Something like moving from effectively 12 Gflops per cycle to 4+ today, versus trial factoring still same speed. Vincent Last fiddled with by diep on 20100808 at 20:25 

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