question on MatMatMult
Matthew Knepley
knepley at gmail.com
Mon Mar 17 17:40:12 CDT 2008
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
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