[petsc-users] Issue using multi-grid as a pre-conditioner with KSP for a Poisson problem

[Mark Adams]

>
>
>
> What are the differences between gamg and mg with -pc_mg_galerkin option
> (apart from the default smoother/coarse grid solver options, which I
> identified by comparing the ksp_view output)? Perhaps there’s an issue with
> the restriction, as you suggest?
>


Not sure if this got answered. GAMG is for unstructured problems. A "pure"
AMG method.

mg with -pc_mg_galerkin is semi-AMG, it still has geometric interpolation,
and it is generally better if you can use it.
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