petsc-users Digest, Vol 11, Issue 17

[Barry Smith]

    This only gives the final residual norm as computed by the Krylov  
method; so depending on your options it may be a preconditioned  
residual norm.

    If you want the true residual norm then you should compute it via  
the formula || b - A*x|| in your Fortran code after the KSPSolve()

    Barry

On Nov 18, 2009, at 2:21 PM, Matthew Knepley wrote:

> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPGetResidualNorm.html
>
>   Matt
>
> On Wed, Nov 18, 2009 at 2:19 PM, <hxie at umn.edu> wrote:
> Hi,
>
> I want to output the true residual norm after calling KSPSolve in a  
> fortran program. I know there is a command option '- 
> ksp_final_residual', but I cannot do this using the PBS job  
> submission. What is the related fortran subroutine for this? Thanks  
> for your help.
>
> Bests,
> Hui
>
>
>
> -- 
> What most experimenters take for granted before they begin their  
> experiments is infinitely more interesting than any results to which  
> their experiments lead.
> -- Norbert Wiener