[petsc-users] gmres restart

[Barry Smith]

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.

   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