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Old 2011-01-01, 16:13   #5
Mr. P-1
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Jun 2003

7×167 Posts

Originally Posted by Mini-Geek View Post
If your goal is to expect to finish the number in the shortest amount of CPU time, (in other words, most efficiently for the systems you have) you should only run the Prime95 default settings, regardless of how many systems are available.
Moreover you should not parallelise any of the factorisation methods with each other, or with the LL, so basically you are talking about using only one machine at a time, (though it may make sense, however, to do P-1 stage 2 on a slower machine with more memory.)

If your goal is to expect to finish the number in the shortest calendar time, you should run as much TF, P-1, and maybe even ECM as you can on as many systems are available, while doing the LL test with as many cores as possible on the fastest hardware available.
In the extreme, you could continue factorisation efforts throughout the entire duration of the LL, though the returns from so doing would diminish rapidly. Specifically you would have an ever reducing probability of finding a factor which would allow you to abort the ever reducing tail end of the LL.

A good compromise might be: 1, Start LL imediately using all cores of your fastest machine. 2, in parallel, use a CUDA compatible GPU to FT to several bits deeper than normal. If you don't have one, there may be people willing to do this for you. 3, again in parallel, do P-1 to "normal" limits, doing stage two on a machine with as much memory as possible. 500MB is recommeded as a "good" amount for normal sized exponents, so probably about 4GB would be good for an exponent this size, but I don't really know. If the LL machine has significantly more memory than any other, and if no other has 4GB, then consider temporarily shifting LL work from that machine to another.

I'm not sure how worthwhile ECM would be. In general, its more expensive than P-1 and less effective as it can't take advantage the 2kp+1 from of Mersenne factors. Like P-1 it wants gobs of memory for stage two, though I don't know how much, compared with P-1.
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