The Trilinos backend isn't in a shape as good as PETSc is, and the
same goes for the Trilinos codebase itself and everything surrounding
it ("community managment").
That said, I believe that Trilinos offers a number of things that are
not included in PETSc itself. For example, the variety of linear
solvers included in Trilinos::Belos is quite large,

BlockCG
BlockGCRODR
BlockGmres
GCRODR
GmresPoly
Gmres
LSQR
Minres
PCPG
PseudoBlockCG
PseudoBlockGmres
PseudoBlockStochasticCG
RCG
TFQMR

Not all of them are interfaced by Dolfin, but I suppose this can be done.
Moreover, ML has a number of AMG options that are not available from
other preconditioning packages; one of them is the important class of
AMG for curl-curl problems.

> I don't think Trilinos nicely supports Schur complement preconditioners

Trilinos::Teko <http://trilinos.sandia.gov/packages/teko/> is designed
for this purpose. I haven't used it myself though.

> That said, my reason for using Trilinos was mainly its nice Python interface,

PyTrilinos is virtually dead.

I think a big selling point of Trilinos is the development that
happens in Trilinos::Tpetra -- it shows great promise in  the HPC
arena when computing large problems in heterogeneous environments (for
example). Currently, Dolfin hooks up to (legacy) Epetra, so adopting
this may be worthwhile.

I do understand Garth's concerns, though, and I don't use the Trilinos
backend too often now. I can see myself in the situation though where
I run Dolfin code in an HPC environment and would like to see what
Trilinos can do for me.

Also, let's not forget about the uBLAS layer which I find
exceptionally useful for debugging purposes. Removing Trilinos alone
would not do away with the abstraction layer Generic*.

Are there other ways of reducing the maintenance burden for the developers?

Cheers,
Nico


On Mon, May 26, 2014 at 5:32 PM, Garth N. Wells <[email protected]> wrote:
> Are there any strong opinions on keeping or removing the Trilinos backend
> from DOLFIN? I ask now because there is a maintenance burden in having both
> (I'm feeling this acutely with the switch to local dof indices), and the
> Trilinos backend gets far less polishing and testing than the PETSc backend,
> which can make a less favourable impression on users who use the Trilinos
> backend.
>
> Another issue is that it is becoming difficult to provide users with a
> common interface to more sophisticated solvers since these are closely tied
> to the design of the underling linear algebra backend.
>
> Garth
>
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