[petsc-users] Composite shell preconditiner

[Alexander Grayver]

On 17.08.2012 16:03, Jed Brown wrote:
>
> Fine, sounds like you are doing divergence cleaning for an 
> incompatible spatial discretization. Since the change lies within the 
> null space of the intended continuous operator, you should be okay. 
> But note that this procedure is fragile and will have different effect 
> with different Krylov methods and preconditioning sides.

Right.
Could you please explain what do you mean by fragile?

>
>     Looks a bit tricky. The number of fgmres iterations then defines
>     number of the cycles correction will be applied, doesn't it?
>
>
> Yes.

If I do this command line only setup:
-pc_type composite -pc_composite_type multiplicative -pc_composite_pcs 
ksp,shell

How does petsc know what ShellPCApply routine to take? I guess I have to 
specify this in the code anyway?


-- 
Regards,
Alexander

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