GMRES as a Geometric Multigrid Smoother

[Thomas Cheetham]

Hi all,

I have a matrix-free code which uses geometric multigrid as a preconditioner (based on step 37). I've found that for my case the Chebyshev smoother does not work well under certain conditions. From literature I think replacing this with few iterations of GMRES as a smoother may work well. However I'm struggling to see how to implement this in deal.ii multigrid framework. Any help in pointing me in the right direction would be greatly appreciated.

Many thanks,

Tom

[Peter Munch]

Hi Tom

you need to impelement MGSmootherBase (see: https://www.dealii.org/developer/doxygen/deal.II/classMGSmootherBase.html) in particular its smooth/apply methods. Here you would call GMRES. This new class is what you would use instead of  MGSmootherRelaxation.

Hope this helps!

Best,
Peter