On 30 July 2015 at 22:10, <20100.delecr...@gmail.com> wrote: > Thanks for the answer! (and sorry for my very late reply) > > Le dimanche 3 mai 2015 18:54:43 UTC+2, Bill Hart a écrit : >> >> >> >> On 3 May 2015 at 12:51, <20100.d...@gmail.com> wrote: >> >>> Hello, >>> >>> I would like to know whether it it is possible to compare a mpz_t and a >>> mpq_t more efficiently than: >>> - creating a mpq_t with denominator 1 >>> - swap the numerator with the mpz_t >>> - call mpq_cmp >>> - swap back the numerator with the mpz_t >>> - free the memory of the mpq_t >>> >> >> Sure. Take a look at the mpq_numref and mpq_denref functions. There is no >> need to create an mpq_t, though you do need a temporary mpz_t for the >> result of the multiplication. >> >> Of course, any function which performed such a comparison would have to >> create this internally anyway. So in terms of efficiency, it's about the >> best you can do. You can special case denominator = 1 or numerator = 0 and >> a few other cases like that. But it's about the best you can do. >> > > I asked the question after I had a look at mpq_cmp. This function first > tries some comparison based on the size of numerators and denominators. So > I deduced that calling mpq_cmp would be faster (in simple cases) rather > than direct cross multiplication even if I had to initialize an mpq_t with > a denominator 1. > > >>> If not, would it be useful to have this as a standalone function (like >>> "mpq_cmp_mpz")? There is a need within Sage [1,2] where often integer and >>> rational types are mixed. >>> >> >> I'd be inclined to just add such a thing as a macro if you need it often. >> It's only about four lines to implement. >> > > What would be this macro? Calling mpq_cmp? Cross multiplication? >
Yes, I intended cross multiplication. You can special case it for denominator = 1, perhaps. Bill. > > Vincent > -- 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.
