[petsc-users] How to implement projection preconditioner?

[Jed Brown]

On Wed, Jun 13, 2012 at 10:54 AM, Abdul Hanan Sheikh <hanangul12 at yahoo.co.uk
> wrote:

> Thanks for reply!
> Well at first look, it looks like that M can be put as precondittioning
> operator for smoother
> where keeping ksp as preonly in pre-smoother context.
> I am not sure, this leads to the preconditioner desired, coz putting M as
> preconditioner in
> pre-smoother alters the residual passed to coarse-grid correction,  i.e.
> CGC corrects the pre-smoothed solution.
>

That's kind of the point of pre-smoothing. Can you explain more precisely
(or just try it).


>
>
>
>   ------------------------------
> *From:* Jed Brown <jedbrown at mcs.anl.gov>
> *To:* Abdul Hanan Sheikh <hanangul12 at yahoo.co.uk>; PETSc users list <
> petsc-users at mcs.anl.gov>
> *Cc:* Abdul - CITG <A.H.Sheikh at tudelft.nl>
> *Sent:* Friday, 8 June 2012, 19:01
> *Subject:* Re: [petsc-users] How to implement projection preconditioner?
>
> Isn't this just putting M and M_H as the preconditioning operator for the
> smoother?
>
> On Fri, Jun 8, 2012 at 11:58 AM, Abdul Hanan Sheikh <
> hanangul12 at yahoo.co.uk> wrote:
>
> Dear all,
> Summer greetings,
> I am back with an other query.
> Before I successfully implement the projection preconditioner which was
> simply
> the coarse grid correction operator P = I - A*(P*A_H*R);
> I implemented this simply keeping both pre and post smoothing dummy in
> PCMG setup.
> Now I need to revise this and re-implement this where I replace A and
> coarse operator A_H with
> preconditioned one i.e. M^-1 A and M^-1 A_H respectively. Thus new
> projection reads as
>
>
> P_new = I - (M^-1 A) {P*(M_H^-1 A_H)*R}
>
> Any suggestion to implement this in Petsc would be appreciated.
>
> Thanking in anticipation.
> with regards, Abdul
>
>
>
>
>
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