It's unbelievable. With v=T[0], all of these take a ridiculous time: sage: V2=v.parent() sage: VQ=V2.change_ring(QQ) sage: vQ=VQ(v) In my code I have had to avoid using change_ring on vectors and matrices for this.
On 25 November 2013 20:07, Jeroen Demeyer <[email protected]> wrote: > Why does this take such a long time? > > sage: M = random_matrix(ZZ,2000,1000) > sage: T = M.change_ring(GF(2)).left_kernel().basis() > sage: %time r = T[0].change_ring(QQ) > CPU times: user 73.49 s, sys: 0.33 s, total: 73.83 s > Wall time: 74.01 s > > Especially compared to > sage: %time r2 = Matrix(T).change_ring(QQ).rows()[0] > CPU times: user 7.40 s, sys: 0.01 s, total: 7.41 s > Wall time: 7.40 s > > Or even > sage: %time r3 = vector(QQ, T[0].list()) > CPU times: user 0.01 s, sys: 0.00 s, total: 0.01 s > Wall time: 0.01 s > > -- > 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 [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sage-devel. > For more options, visit https://groups.google.com/groups/opt_out. -- 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/groups/opt_out.
