Hi, I posted a ticket this morning about some profiling I did on product of matrices (see http://trac.sagemath.org/ticket/16116). Here is a minimal example:
sage: PR=PolynomialRing(QQ,[x]) > sage: I=Ideal(x^2 - 1/2*x - 1/4) sage: Q=PR.quotient(I) sage: elmt_uni=matrix(Q,[[-2*x, 1, 6*x + 2],[-2*x, 2*x, 4*x + 1],[0,0,1]]) sage: %timeit elmt_uni*elmt_uni 1000 loops, best of 3: 1.46 ms per loop > > sage: CF.<F>=CyclotomicField(2*5) sage: f5=(F+~F)/2 sage: m=matrix(CF,[[-2*f5, 1, 6*f5 + 2],[-2*f5, 2*f5, 4*f5 + 1],[0,0,1]]) sage: type(m) <type 'sage.matrix.matrix_cyclo_dense.Matrix_cyclo_dense'> sage: m.parent() > Full MatrixSpace of 3 by 3 dense matrices over Cyclotomic Field of order 10 > and degree 4 sage: %timeit m*m 100 loops, best of 3: 1.98 ms per loop > Both computation seems to take the same time although more complicated example show that the first method is faster. Then, I disactivated the verification on cyclotomic fields on line 962 of the file /src/sage/matrix/matrix_space.py to get a matrix_generic_dense instead of matrix_cyclo_dense. It gives me: sage: CF.<F>=CyclotomicField(2*5) > > sage: f5=(F+~F)/2 > > sage: m=matrix(CF,[[-2*f5, 1, 6*f5 + 2],[-2*f5, 2*f5, 4*f5 + 1],[0,0,1]]) > > sage: m.parent() > > Full MatrixSpace of 3 by 3 dense matrices over Cyclotomic Field of order 10 > and degree 4 > > sage: type(m) > > <type 'sage.matrix.matrix_generic_dense.Matrix_generic_dense'> > > sage: %timeit m*m > > 1000 loops, best of 3: 251 µs per loop > > The question is now: what is the method *_matrix_times_matrix_,* located in the module *matrix_cyclo_dense.pyx*, doing so that it takes so much time compared to the usual generic multiplication of the module matrix_generic_dense? Is there a known use case when the multiplication in matrix_cyclo_dense is faster than the generic one? Thanks, JPLab -- 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 http://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
