On Mon, Mar 17, 2008 at 5:28 PM, Randall Mackie <rlmackie862 at gmail.com> wrote: > If I want to compute H = L^T L where L is a sparse matrix which is an > approximation to the > laplacian, and hence H is the biharmonic (also sparse), and if I have L as > an MPI matrix > in PETSc, will MatMatMult work for this (assuming I create the transpose of > L first). > > In other words, does MatMatMult look at the non-zero structure only that > would result, > or does it think the result is a dense matrix?
It builds the structure dynamically, which explains the "fill" argument. This is not a great thing to do unless you have no idea how to form it directly. Matt > Thanks, Randy -- 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
