"Marco Bodrato" <bodr...@mail.dm.unipi.it> writes: > Ciao, > > Il Dom, 18 Agosto 2019 9:44 am, Niels Möller ha scritto: >> Do we have all needed gcd_11 so we can switch to using it, without >> performance regressions? > > I glanced at mpn/generic/gcd.c > > The initial comment says: > /* mpn/gcd.c: mpn_gcd for gcd of two odd integers. > > A comment inside slightly relaxes the conditions with: > /* Due to the calling convention for mpn_gcd, at most one can be > even. */ > > ...but I can not find any documented restriction (odd/even) in the manual.
This seems a bit confused, yes. Long ago, mpn_gcd mpn_gcd required one input odd, but documentation was relaxed with change 71efb0367192 in 2011. The hgcd loops don't care about odd/even, To me it looks like the code path mpn_gcd -> gcd_22/gcd_2 will fail if both inputs to mpn_gcd are even, also before recent changes. And we have no separate unittests; the gcd tests call mpz_gcd, which takes out factors of two before calling mpn_gcd. So we either have to update the docs to say that at least one of the inputs to mpn_gcd must be odd, or handle common factors of two before calling gcd_11 and gcd_22. Regards, /Niels -- Niels Möller. PGP-encrypted email is preferred. Keyid 368C6677. Internet email is subject to wholesale government surveillance. _______________________________________________ gmp-devel mailing list gmp-devel@gmplib.org https://gmplib.org/mailman/listinfo/gmp-devel
