On Mon, May 19, 2008 at 8:34 AM, Anders Logg <[EMAIL PROTECTED]> wrote: > On Mon, May 19, 2008 at 08:30:20AM -0500, Matthew Knepley wrote: >> On Mon, May 19, 2008 at 8:20 AM, Anders Logg <[EMAIL PROTECTED]> wrote: >> > It looks to me like the storage needed is indeed n^2*num_cells. I'm >> > not fluent in Fortran, but that's how I interpret this line: >> > >> > atw(idxatw(el,li,lj)) = atw(idxatw(el,li,lj)) + Atmp(li,lj) >> > >> > This looks expensive (in terms of memory), but maybe not that >> > expensive? >> >> I think I should make the aggregation point again. The above line executes >> a function call for insertion of every value. This is a lot of >> overhead, > > No, I think the above code would be very much faster than PETSc, but > use more memory. The way I interpret it, atw is an array and idxatw is > a *dense* rank 3 tensor so there's no searching, only lookup.
Okay, I see what the notation is now. That would mean a lot of storage, probably more than the matrix itself. >> not only >> for the call, but setting up loop bounds etc. That is why MatSetValues takes >> logical blocks, exactly what you get from FEM, I believe this could be the >> difference between our timing results. > > No, the above code is not what we use in DOLFIN. We use MatSetValues > with blocks. The above code is femLego Fortran code. Okay, if it is blocked than we should have the same numbers. Matt > -- > Anders > _______________________________________________ > DOLFIN-dev mailing list > [email protected] > http://www.fenics.org/mailman/listinfo/dolfin-dev > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
