MatGetSubMatrix question

Lisandro Dalcin dalcinl at
Tue May 26 12:11:47 CDT 2009

On Mon, May 25, 2009 at 10:20 AM, Jed Brown <jed at> wrote:
> Is it really necessary that iscol be a sequential index set that covers
> all columns, with csize selecting the local columns?  I realize this
> might be natural/easy for AIJ formats, but it feels clumsy (not to
> mention not scalable due to the ISAllGather).

Your are right, this is not scalable, but...

> I'm guessing this is a relic from when IS was not a real parallel
> object.  Am I missing some deep reason for this interface, or could
> iscol be parallel and csize be dropped?

unless things have changed very recently (after 3.0.0 release), IS is
far from being a real parallel object.

Lisandro Dalcín
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594

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