Please do file issues on slicing. The implementations have a bit of effort put into them, but there is most likely room for a lot of optimization. It would be useful to have the exact cases where performance doesn't meet expectations.
In general for stiffness matrix assembly, I believe that using `sparse(I,J,V)` should be the way to go, if it works. I should also write some performance notes for working on sparse matrices too. -viral On Wednesday, January 7, 2015 11:26:09 PM UTC+5:30, Tim Holy wrote: > > flipping (or, I guess, rotation) has already been fixed by kshyatt, who > has been > writing tests. (!) > > https://github.com/JuliaLang/julia/pull/9593 > > I guess the flip is more of a mirror symmetry, but you should be able to > copy > her pull request to implement it. (Please do submit as a pull request.) > > The slicing thing also needs to be fixed, that would be good to open as an > issue. > > --Tim > > > On Wednesday, January 07, 2015 12:35:48 PM Stefan Karpinski wrote: > > I suspect this is precisely the case. Please do open an issue. > > > > On Wed, Jan 7, 2015 at 12:24 PM, Kevin Squire <[email protected]> > > > > wrote: > > > I would suggest doing a quick search on github for any issues related > to > > > sparse matrices, and if none are relevant, opening a new one. One > likely > > > possibility is that neither function has been specialized for sparse > > > matrices, and that the general fallback version of these functions are > > > slow > > > for sparse matrices. In either case, a specialized function should be > > > easy > > > to code. > > > > > > Cheers, > > > > > > Kevin > > > > > > On Wed, Jan 7, 2015 at 9:20 AM, Christoph Ortner < > > > > > > [email protected]> wrote: > > >> I don't have a solution, but a related comment: slicing of large > sparse > > >> matrices is very slow too. E.g., I like to assemble a stiffness > matrix > > >> (for > > >> a PDE) with free boundary conditions and then impose clamped > boundaries > > >> by > > >> taking a subset of the matrix, > > >> > > >> B = A[Ifree, Ifree] > > >> > > >> this is so slow that I had to completely give up on it and rewrite > all my > > >> assembly codes. > > >> > > >> I suspect that the flipxx functions and this are a similar issue? > > >> > > >> Is there already an issue filed for this? > > >> > > >> Christoph > >
