Re: PETSc sparsity

["Matthew Knepley" <knepley@xxxxxxxxx>]

Also, I have talked to Wolfgang many times about this. I am a firm
believer in eliminating the boundary values during assembly at the
element level. PETSc provides an easy mechanism for this. By default,
all negative indices in calls to VecSetValues and MatSetValues are
ignored.

 Matt

On 6/15/07, Mark Adams <adams@xxxxxxxx> wrote:
> Just a note, my way is much simpler - its two lines of code in a loop
> over the boundary nodes, followed by an MatAsseblyBegin/End, and you
> don't have to deal with parallel issues explicitly - PETSc does.  For
> my FE codes the cost of this (dumb) way is negligible, PETSc
> implements these methods pretty well.
>
> Mark
>
> On Jun 15, 2007, at 4:28 PM, Toby Young wrote:
>
> >
> >
> > Barry,
> >
> > Thank you for an interesting response.
> >
> >>   For algorithms that require dealing with the sparsity structure of
> >> the matrix we generally just include the appropriate private
> >> include file
> >> for the matrix format and access the data directly in the
> >> underlying format.
> >
> > Can you please elaborate. What do you mean by "the appropriate privat
> > include file for the matrix"? Sorry, I got lost there.
> >
> > Best,
> >       Toby
> >
> > -----
> >
> > Toby D. Young (Adiunkt)
> > Department of Computational Science
> > Institute of Fundamental Technological Research
> > Polish Academy of Science
> > Room 206, ul. Swietokrzyska 21
> > 00-049 Warszawa, POLAND
> >
>
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What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which
their experiments lead.
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