[petsc-users] gmres restart

[Verena Kuhlemann]

On Mon, Nov 29, 2010 at 6:08 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> On Nov 29, 2010, at 5:04 PM, Verena Kuhlemann wrote:
>
> > Hello,
> >
> > I have a (hopefully) quick question about setting the restart for gmres.
> >
> > I set the restart to be 50, but when I use KSPView it looks like GMRES
> > still uses a restart of 30. It is possible that I overwrite my settings
> > somehow? Here is the relevant part of my code:
> >
> > KSPCreate(PETSC_COMM_WORLD,&ksp);
> > KSPSetOperators(ksp,A,A,DIFFERENT_NONZERO_PATTERN);
>
>    KSPSetType(ksp,KSPGMRES);
>
> > KSPGMRESSetRestart(ksp,50);
>
>   You have not set the type to GMRES by this point, therefor the setting of
> restart is ignored. Must set the type before this.
>

Ah, I thought I don't have to set it, since GMRES is the default. Now it
works, thanks.










>
>   BTW: we highly recommend just calling KSPSetFromOptions() and setting
> parameters from the options database, much nicer IOHO then hardwiring in the
> source code.
>
>   Barry
>
>
> > KSPSetInitialGuessNonzero(ksp,PETSC_TRUE);
> > KSPSetTolerances(ksp,1.e-12,1.e-12,PETSC_DEFAULT,100000);
> > KSPSetUp(ksp);
> > KSPGetPC(ksp,&pc);
> > PCSetType(pc,PCNONE);
> > KSPView(ksp,PETSC_VIEWER_STDOUT_WORLD);
> > KSPSolve(ksp,b,x);
> >
> >
> > Thanks,
> > Verena
>
>


-- 
Verena Kuhlemann
Ph.D. Candidate
Mathematics and Computer Science Department
Emory University
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