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-   -   P-1 using P95 for stage 1 & gmp-ecm for Stage 2? (https://www.mersenneforum.org/showthread.php?t=21511)

Gordon 2016-08-17 21:55

P-1 using P95 for stage 1 & gmp-ecm for Stage 2?
 
Hi,

I know that you can do ecm using the above combo as that is how I'm tackling the (very) small exponents with no factor known.

Is it possible to do what the title says?

For arguments sake

M4007 do P-1 with B1=2e12

LaurV 2016-08-18 03:43

If you think about taking stage 1 file saved by P-1 and use it for stage 2 of ECM, the answer is "no".
Anyhow, you can do P-1 with a GPU, much faster, for both stage 1 and 2, and it is not limited to ~1200 bits like the gpu-ECM is.
That because P-1 for mersenne numbers is very efficient, moving the problem from "q-1 is smooth", to "k is smooth", where q=2kp+1 is the factor you are looking for, which means about "2p times" faster than ecm (well, that is a coarse approximation, and not exactly correct).


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