Dear Mikhail, > From: Mikhail Hogrefe <mikhailhogr...@gmail.com> > Date: Mon, 4 Mar 2019 21:44:50 -0500 > > I was digging around in the GMP 6.1.2 source, and I noticed something in > mpn/generic/mul_fft.c. > > In mpn_mul_fft_decompose, there is an if statement checking 'dif > Kl', > which is equivalent to 'nl > 2 * K * l'. But there is a comment above the > function saying 'We must have nl <= 2*K*l.', suggesting that the first > branch of the if is never taken. > > Maybe you're already aware of this, but if not I wanted to let you know. > > Best, > Mikhail Hogrefe
good remark. Indeed in the mul_fft.c file, it seems this code is dead. However if mpn_mul_fft_decompose is exported, for example if one wants to compute a product of two numbers modulo 2^n+1, where the two numbers have more than 2n bits, then this branch might be useful. Anyway this code is now obsolete (see [1] and [2]). Best regards, Paul Zimmermann [1] http://homepages.loria.fr/PZimmermann/papers/#fft [2] https://gmplib.org/devel/ "This will largely depend on ongoing work on FFT multiplication" _______________________________________________ gmp-devel mailing list gmp-devel@gmplib.org https://gmplib.org/mailman/listinfo/gmp-devel