Ciao, Il Ven, 16 Ottobre 2020 1:47 am, Seth Troisi ha scritto: > On Thu, Oct 15, 2020 at 10:44 AM Niels Möller <ni...@lysator.liu.se> >> Seth Troisi <brain...@gmail.com> writes: >> > Technically I can restructure the code to make both use with >> mpz_fdiv_ui
>> > static int >> > findnext (mpz_ptr p, >> > - unsigned long(*nextmod_func)(const mpz_t, unsigned long), >> > + char direction, >> > void(*nextseq_func)(mpz_t, const mpz_t, unsigned long)) >> I see. I don't think it's worth taking out a function pointer if it's >> replaced with a flag and a couple of if statements. It would be neat if >> it could be done similarly to findnext_small Well, both mpz_fdiv and mpz_cdiv have if statements in their code, to differently handle positive and negative numbers. We can avoid those branches using tdiv, and add one here (the compiler may use a cmov). I mean: /* we have 0 < prime <= 150000001 < 2^28, because of calculate_sievelimit */ #if GMP_NUMB_BITS >= 28 m = mpn_mod_1 (PTR (p), SIZ (p), (mp_limb_t) prime); #else m = mpz_tdiv_ui(p, prime); #endif m = (diff > 0) ? prime - m : m; >> with diff being +2 or -2 (and possibly generalized further), and no >> conditionals, e.g., >> >> mpz_add_si (p, p, diff * (odds_in_composite_sieve-1)); We don't have such a function :-) But adding a static function like that here, assuming that p is always positive and greater than |si|, with a single branch... can be a good idea. Ĝis, m _______________________________________________ gmp-devel mailing list gmp-devel@gmplib.org https://gmplib.org/mailman/listinfo/gmp-devel
