"Matt J" wrote in message <firstname.lastname@example.org>... > "Bruno Luong" <email@example.com> wrote in message <firstname.lastname@example.org>... > > "Matt J" wrote in message <email@example.com>... > > > > >In fact, the sparse matrix multiplication is probably even handicapped relative to accumarray, since it has to search through x for the appropriate x(J), > > > > There is no such step in sparse multiplication. > ============= > > Meaning that y=A*x is generated by looping over columns of A instead of rows? Even if so, how would that explain the speed difference? ================
Anyway, my point remains. Sparse matrix multiplication has to perform multiplications with the x(j) somewhere, whereas accumarray, in my tests, does not. So sparse mult. is further handicapped.