[petsc-users] multigrid preconditioning and adaptivity

[Matthew Knepley]

On Mon, Mar 7, 2016 at 6:58 AM, Lukasz Kaczmarczyk <
Lukasz.Kaczmarczyk at glasgow.ac.uk> wrote:

> Hello,
>
> I run multi-grid solver, with adaptivity, works well, however It is some
> space for improving efficiency. I using hierarchical approximation basis,
> for which
> construction of interpolation operators is simple, it is simple injection.
>
> After each refinement level (increase of order of approximation on some
> element) I rebuild multigrid pre-conditioner with additional level. It is a
> way to add dynamically new levels without need of rebuilding whole MG
> pre-conditioner.
>

That does not currently exist, however it would not be hard to add, since
the MG structure jsut consists of
arrays of pointers.


> Looking at execution profile I noticed that 50%-60% of time is spent on
> MatPtAP function during PCSetUP stage.
>

Which means you are using a Galerkin projection to define the coarse
operator. Do you have a direct way of defining
this operator (rediscretization)?

  Thanks,

    Matt


> Kind regards,
> Lukasz




-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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