How to Use Prime95: Advanced Menu - ECM

# ADVANCED MENU - ECM

## ECM

The ECM choice lets you factor Mersenne numbers using the Elliptic Curve Method of factoring. Select a few exponents and bounds to factor from the http://www.mersenne.org/ecm.htm web pages.

Note: You do not reserve exponents to work on, several people can do ECM factoring on the same exponent. The program uses a random number generator to select elliptic curves to test. You must email results to me at woltman@alum.mit.edu - PrimeNet does not support ECM factoring. WARNING: ECM does not adhere to the memory limits specified in the Options/CPU dialog box. ECM requires a minimum of 192 times the FFT size. Thus, ECM factoring of F20 which uses a 64K FFT will use a minimum of 192 * 64K or 12MB of memory. You can also edit the worktodo.ini file directly. For example:

ECM=751,3000000,0,100,0,0,0,0

The first value is the exponent. The second value is bound #1. The third value is bound #2 - leave it as zero. The fourth value is the number of curves to test. The fifth value is no longer used. The sixth value is the specific curve to test - it is only used in debugging. The seventh value is 0 for 2^N-1 factoring, 1 for 2^N+1 factoring. The eighth value is no longer used.