Two 10-lines functions
tg at gmplib.org
Wed Jan 20 22:57:51 CET 2010
"gianrico.fini at terra.es" <gianrico.fini at terra.es> writes:
I was challenged... the challenge was: write a 10-lines substitute for the
There is no function mpn_mulmod_2expp1 in any version of GMP. (But an
early version of mpn_mulmod_bnm1 was called something like that.)
It computes the product of xp and yp modulo 2^b+1. It assumes that xp and yp
have exactly b bits.
What does it mean that "xp has exactly b bits"? That 2^(b-1) <= xp <
2^b? It looks like your code does not handle any b value, or there
should be some shifting.
This function is needed for a benchmark checking if some Fermat's numbers are
prime or not.
I'd suspect mpn_mul_fft might be directly applicable for that. It has
existed in GMP since the dark ages...
I am not sure what do do with your contribution, and where it would fit
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