Unless I am being monumentally stupid (possible), the documentation for the mpz_gcdext function looks totally different between GMP-5.0.3 and GMP-5.0.4, so either there was a change of normalisation somewhere in there, or the documentation never specified what was supposed to happen in this case before that point.
Either way, I think we are pretty much off the hook here. We now use the gmp-5.0.5 interface. This may break some doctests in Sage. Bill. On 9 June 2015 at 21:07, Bill Hart <goodwillh...@googlemail.com> wrote: > Sorry it took so long for me to look into this. Finding even an hour of > time to work on MPIR for the last year or so has been almost impossible. > > I can confirm that even GMP 5.0.5 had: > > * if |a| = |b| then s = 0, t = sgn(b) > > So in the example Jeroen gave, the result should clearly be s, t = 0, 1. > > Unfortunately, MPIR-2.6.0 did not have this, so I would consider this a > bug in earlier versions of MPIR, since we are supposed to be compatible > with GMP. It's clearly right in MPIR-2.7.0-alpha, since we use their xgcd > code not our own. > > Having said that, I don't really know the history of this function in GMP, > except that at some point, ages ago, there was a change in normalisation. > There may have been further work since then, I didn't check. So we might > just be late catching up. > > What I will now do is update both our test code and documentation to match > that of GMP for this function. This ought to ensure compliance to their > interface, for now. > > Bill. > > On 6 December 2014 at 00:49, Jean-Pierre Flori <jpfl...@gmail.com> wrote: > >> Bill, sorry to bump that post, but i would really like to see MPIR >> updated in Sage for my work. >> >> >> On Thursday, November 27, 2014 6:40:15 PM UTC+1, Jean-Pierre Flori wrote: >>> >>> >>> >>> On Monday, November 24, 2014 3:06:49 PM UTC+1, Jean-Pierre Flori wrote: >>>> >>>> Ok, the change was to be expected. >>>> The previous code swapped the args order between the calls to >>>> mpz_gcdext and mpz_gcdext in case a==b, and then the output. >>>> I guess it's not to be considered a bug then. >>>> >>>> I have no idea if anything is random in there though. >>>> >>> Bill, any comment on that? >>> It would be nice to upgrade MPIR to any 2.7.0 alpha in Sage if that's >>> possible :) >>> >> > -- You received this message because you are subscribed to the Google Groups "mpir-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to mpir-devel+unsubscr...@googlegroups.com. To post to this group, send email to mpir-devel@googlegroups.com. Visit this group at http://groups.google.com/group/mpir-devel. For more options, visit https://groups.google.com/d/optout.
