On 2012-12-05, John Cremona <john.crem...@gmail.com> wrote: > ------=_Part_32_14834482.1354721238473 > Content-Type: text/plain; charset=ISO-8859-1 > > > > On Wednesday, December 5, 2012 1:56:55 PM UTC, Jason Grout wrote: >> >> On 12/5/12 7:46 AM, John Cremona wrote: >> > I don't know why this takes so long: >> > >> > I have a field F (a snumber field of high degree, 288 in fact) and >> > want to create a 100x100 matrix over F from a list of 100 lists of 100 >> > elements of F, while I will call "entries". If I do >> > >> > M = Matrix(entries) >> > >> > which certainly works fine with smaller examples, then I get tired of >> > waiting (after 10 or 15 minutes) and cannot even interrupt with >> > Ctrl-C. But if I do >> > >> > M = copy(MatrixSpace(F,100).zero_matrix()) >> > for i in range(100): >> > for j in range(100): >> > M[i,j] = entries[i,j] >> > >> > it works in a few seconds. So what is going wrong with the first >> (simpler) way? >> >> If you just do Matrix(entries), it tries to guess the right base ring >> (using the Sequence() command, IIRC). In the second example, you are >> explicitly telling Sage the base ring. I wonder if that is what is >> going on. To check, can you try doing: >> >> matrix(F, entries) >> >> > That is slow too. Try > > > Q1092.<z>=CyclotomicField(1092) > entries = [[Q1092.zero_element() for i in range(100)] for j in range(100)] > M=Matrix(Q1092,entries) > > which takes a long time (*) and cannot be interrupted with Ctrl-C.
from what Volker wrote, it can be gathered that M=Matrix(Q1092,entries,sparse=True) might work much faster. Dima -- You received this message because you are subscribed to the Google Groups "sage-support" group. To post to this group, send email to sage-support@googlegroups.com. To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support?hl=en.
