[petsc-users] V-cycle multigrid with matrix shells

[Jed Brown]

On Tue, May 17, 2011 at 20:32, Sylvain Barbot <sylbar.vainbot at gmail.com>wrote:

> You're right, I should experiment more with assembled matrices before
> choosing a solver/preconditioner. Could you be more specific about the
> command line options that I could test. I have a version of the code
> with assembled sparse matrices (default format). I tried running with
> the option -pc_type mg and got the following error:
>

You need to set grid information or interpolation operators for this to
work. If you have a grid hierarchy, you can set it by following that chapter
of the user's manual (which I think you were trying to do with matrix-free
operators everywhere). If you use a structured grid, DMMG is quite
convenient.

(petsc-dev does not seg-fault on the configuration you gave because the data
structure has been improved)
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