[petsc-users] Roles of ksp_type and pc_type

[Massimiliano Leoni]

In data giovedì 13 novembre 2014 06:39:38, Matthew Knepley ha scritto:
> On Thu, Nov 13, 2014 at 6:24 AM, Massimiliano Leoni <
> 
> This is not exactly right because here you are just using additive
> fieldsplit.
AFAI understood from the user manual, this should be right because my 
preconditioner is block diagonal, so I want to use block Jacobi.

If I used the other one, P = [[C,O],[B,Mp/nu]] then I would need a 
multiplicative fieldsplit because this would be lower triangular.

Is this correct?

> The mass matrix
> is a good preconditioner for the Schur complement, not the zero matrix.
> Take a look at these slides:
What do you mean?
I know from theory that the preconditioner I am using is optimal [iteration 
number independent of grid size].

I read the slides and the manual and the Schur complement is what I was 
talking about earlier, so it's not what I wanna do now -- even though knowing 
that it's so easy to implement my be very useful.

Anyway, thanks for the slides, they have been enlightening on the power of 
command line options!
 
>   Thanks,
> 
>     Matt
> 
Thanks again,
Massimiliano