[Trilinos-Users] [EXTERNAL] blocked problems

[Nico Schlömer]

Thanks for the advice.
I guess before venturing into the depths of Thyra I'll first bite the
bullet in jiggle with explicit insertion/dissection of Epetra_Vectors.
To be revisited.
On Aug 3, 2012 9:00 PM, "Phipps, Eric T" <etphipp at sandia.gov> wrote:

> Hi Nico,
>
> If possible you are better off using Thyra for this.  Thyra has much
> better support for blocked operators and vectors with little memory
> overhead.  You CAN use EpetraExt's block vectors for this (which is what I
> use in Stokhos) but it is a pain because Epetra_Vector's don't have a
> clone method.  Hence your input and output vectors for your blocked
> Apply() are not necessarily block vectors themselves (but are map
> equivalent to blocked vectors) and thus you have to create a view of them
> as blocked vectors to get access to the blocks.  If you want to do this in
> your model evaluator too, it gets even more messy to go back and forth
> between the blocked and non-blocked interfaces.
>
> -Eric
>
> On 8/3/12 12:22 PM, "Nico Schlömer" <nico.schloemer at gmail.com> wrote:
>
> >Hi all,
> >
> >I would like to extend a (let's say) linear system A by system blocks
> >E=(A, B; C, D) without disturbing the circles of A (which lives in an
> >EpetraExt::ModelEvaluator). Given a map mapA for and a map mapE for E,
> >matrix vector multiplication Y=E*X could certainly be implemented by
> >first dissecting X, copying over its entries into x, perform y=A*x,
> >copy its values into Y, and do the rest of the blocks in a similar
> >fashion. Since all this copying forth and back seems wasteful, I was
> >wondering if there's a better alternative. In principle, there could
> >be a vector/operator class stack that sticks a bunch of Epetra_Vectors
> >and does the right thing for matrix-vector multiplication.
> >I just looked at EpetraExt::BlockVector and friends which does sound
> >promising by its name, but I can't quite get the hang of how it's
> >supposed to be used. May it isn't what I want after all.
> >
> >Anyone with any experience here?
> >
> >Cheers,
> >Nico
> >
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>
>
>
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