Quote:
Originally Posted by rogue
mmff is far faster than dmdsieve for smaller exponents. I don't know if it has a limit for larger exponents. If it does, then it probably wouldn't be difficult to create a "dwdsieve".

Looking at the source code for mmff, it appears the limits are
Exponents 31, 61, 89, 107, 127 for double Mersennes and
Exponents <= 223 for Fermat numbers.
Largest bit level it can test depends on the exponent (see lines 356455 of mfaktc.c in the source of mmff).