On Aug 20, 2009, at 2:15 AM, Tim Kroeger wrote:

> I see that there is now a Preconditioner class in libMesh that has not
> been there in earlier times.  Is that in a usable state?

Yes it is... in fact you've probably already been using it!  The  
PetscPreconditioner gets used by default now.

> Can it reuse a precoditioner between successive solves without  
> setting it up
> again?

It can if you create a Preconditioner that acts that way.  It sounds  
like what you might want to do is create your own Preconditioner  
class... maybe inheriting from PetscPreconditioner and then override  
the init() method so that it doesn't clear the preconditioner.  Then  
you might also want to create your own clear() method that does clear  
the preconditioner... and call this manually whenever you want to  
reset it.

> Is there any tutorial about how to use it?

There isn't... but it's fairly straightforward.  Just create an  
instance of a Preconditioner class and then call  
attach_preconditioner() on the linear/nonlinear solver you are  
using... ie:

system.linear_solver->attach_preconditioner(my_prec);

We do this sometime before initing our equation systems object.

Hope that helps,

Derek

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