On Friday, 11 November 2016 21:00:49 UTC+1, parisse wrote: > > > > Le vendredi 11 novembre 2016 07:03:46 UTC+1, Bill Hart a écrit : >> >> 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. >> > > I'm using a trick for the last step of psrgcd: since the gcd should be of > degree 6 wrt y (obtained by evaluation of other variables), when I have the > remainder of degree 6 (1276 monomials), I check that the division from the > previous remainder (102 monomials) with the primitive part of this > remainder is exact, this saves one pseudo-division. >
I was looking at the source code yesterday and noticed that you figure out the likely degree of the gcd, but I couldn't figure out where it was actually used. But now I think I see where you are using it. > Looking how the content (188 monomials) is computed, it's done by exact > divisions only (it's the leading coefficient up to trivial coefficients). > Can you give me a hint where this is implemented. I didn't find this yesterday. It's a nice trick. Bill. -- 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.
