I assume you are using the modular algorithm to remove the final lot of content at the end of the psr algorithm. Otherwise the algorithm takes quite a long time, since even if we remove the known factors of the content along the way, as specified by the algorithm, the result is far from primitive, and so computing the content in the final step of the algorithm takes a long time.
Bill. On Wednesday, 9 November 2016 20:24:56 UTC+1, parisse wrote: > > > > Le mercredi 9 novembre 2016 17:42:32 UTC+1, Bill Hart a écrit : >> >> I implemented a multivariable psr GCD algorithm in Julia and now the >> timings are as follows: >> >> * if z or x is the main variable, it takes a long time (too long to wait >> for) >> >> * if t or y is the main variable it takes 0.1 - 0.2s on average, >> depending on the exact ordering, with the one exception below >> >> * for variables in the order y, x, z, t with y the main variable, it >> takes 1.1s >> >> I have to admit this was about my fourth attempt at implementing the psr >> algorithm. I settled on a sparse univariate format for the main variable >> and sparse distributed format for the remaining variables. >> >> Of course there are much better algorithms for sparse gcds like this. >> Funnily enough, Magma takes 4s, though its timings presumably don't depend >> on the ordering, since they are proper sparse gcd algorithms. >> >> > Comparing with my own timings (0.1s for psrgcd and 18s for modular gcd), I > would guess that Magma is using the modular gcd algorithm and does not have > heuristics to select psrgcd unlike giac. > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
