SNESSetUp() and matrix-free options

Lisandro Dalcin dalcinl at
Thu May 7 15:00:26 CDT 2009

On Wed, May 6, 2009 at 5:53 PM, Barry Smith <bsmith at> wrote:
>   It is ok with me if you try moving it all.

Ok, I've already started to work on this.

1) I would like to condensate -snes_mf_operator and -snes_mf_operator2
in a single option, were you have to pass the version, 1 or 2 (the
fist by default). It seems that version 2 does not work on all
configurations, so what to do if version 2 is selected? Ignore it (as
currently done)? Generate a PETSC_ERR_SUP?

2) What should happen if a user pass BOTH options -snes_mf and
-snes_mf_operators? Error? One of them should overrides the other?

3) I would like to add a call to set matrix-free programatically...
something like SNESSetUseMFFD(snes,...). Any signature suggetions
regarding my previous discussions about the many options?

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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