[petsc-dev] controlling vector values while doing matrix free operations

[Bobby Philip]

Hmmmm..sorry guys - the entire thread got put away in a folder by my mail reader and I just discovered all your emails :-)

SNESVI looks interesting but as someone pointed out I am using matrix free. And as I understand from Barry a matrix free version of SNESVI is not implemented. The idea of flipping the sign seems to be a poor mans approach that might work for me though I would still need some mechanisms in SNES to put the hooks in.

Bobby

On Dec 14, 2011, at 10:45 PM, Jed Brown wrote:

> On Wed, Dec 14, 2011 at 19:40, Dmitry Karpeev <karpeev at mcs.anl.gov> wrote:
> The trouble is that the constraints can get "eliminated" only when they become active. 
> 
> That's not what I meant. I meant to transform the algebraic system so that those extra variables were eliminated. The point is that we tend to put a lot of effort into designing effective preconditioners for a standard formulation (e.g. conservative variables), and that is partly lost of we have this other system in which the evaluations of constitutive relations are added explicitly.

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