[petsc-users] Petsc with ML and ILU

[Jed Brown]

Lucie Freret <lfreret at arrow.utias.utoronto.ca> writes:

> Hello,
>
> I would like to solve linear systems using Gmres preconditioned by ML  
> and use ILU(0) on all levels (mg_coarse and mg_levels_x).
> As I have MATMPIAIJ matrix, I'm using
> -ksp_type gmres
> -pc_type ml
> -mg_levels_ksp_type preonly (-mg_coarse_ksp_type preonly)

This should be -mg_levels_ksp_type richardson (the default when using
ML), which will compute a residual as necessary before applying the
preconditioner.  Note that this may need damping, or you could use
-mg_levels_ksp_type chebyshev to compute a spectral estimate to combine
damping and targeting a range of the spectrum.
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