[Dune] How to use AMG with the constructor given below ?

[Markus Blatt]

Hi Benedikt,


On Tue, Nov 22, 2011 at 04:44:31PM +0100, Benedikt Oswald wrote:
> Dear Dune,
> 
> I need to instantiate the AMG preconditioner so that I can specify a specific coarseSolver
> since my problem does not work with the default behavior of AMG, i.e.
> 
> "Construct an AMG with an inexact coarse solver based on the smoother.
> 
> As coarse solver a preconditioned CG method with the smoother as preconditioner will be used. The matrix hierarchy is built automatically."
> 
> 
> Thus, I would like to use this constructor
> 
> Dune::Amg::AMG< M, X, S, PI, A >::AMG	(	const OperatorHierarchy & 	matrices,
> CoarseSolver & 	coarseSolver,
> const SmootherArgs & 	smootherArgs,
> const Parameters & 	parms	 
> )

May I ask why you cannot live with the default behaviour?

If you have parmetis and SuperLU installed, the default behaviour is
to agglomerate the data  onto fewer processor until eventualy all data
on the coarsest level is on only one processor. To solve this coarse
level system  SuperLU is solved.

I always used this approach.

If that is not sufficient, I need to take a look at the code for
specifying the coarsesolver, which I fear has not been tested lately.

Cheers,

Markus

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