On Tue, Jul 22, 2008 at 10:05 AM, Martin Sandve Alnæs <[EMAIL PROTECTED]> wrote: > UFC 1.1 already has a function for tabulating the number of dofs > associated with each mesh entity, but I don't think FFC implements UFC > 1.1 completely yet. Shouldn't this be all that's needed from FFC for > DOLFIN to compute/estimate the max non-zeroes per row? Sum the local > dimension of all elements and subtract the number of dofs for each > entity shared by neighbouring elements.
I am not sure how it is implemented in UFC, but note that the algorithm stated above is inadequate to allocate both diagonal and offdiagonal blocks. Matt > -- > Martin > > > 2008/7/22 Garth N. Wells <[EMAIL PROTECTED]>: >> I've been testing assembly with various back-ends, and the bottleneck is >> std::map::insert(..). I don't see an easy away around this which would >> yield the complete sparsity pattern. >> >> For various back-ends (PETSc, MTL4, and perhaps Trilinos), I would >> suggest that we go back to how we initialised matrices before the >> introduction of the sparsity pattern, where based on the number of >> neighbours to each cell and the finite element dimension, the maximum >> number of non-zeroes per row was estimated. With this information, there >> is no time overhead in assembling PETSc and MTL4 matrices relative to >> using the complete sparsity pattern. >> >> A more sophisticated but complex approach would be to allow FFC to help >> compute the maximum number of non-zeroes. How hard would it be for FFC >> to compute the maximum number of non-zeroes per row given the number of >> neighbours of a mesh entity? Using FFC, it would be possible to take >> into account the type of finite element. >> >> Garth >> _______________________________________________ >> DOLFIN-dev mailing list >> [email protected] >> http://www.fenics.org/mailman/listinfo/dolfin-dev >> > _______________________________________________ > 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
