[petsc-users] MG Preconditioning

[Matthew Knepley]

On Fri, Aug 31, 2012 at 10:05 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Fri, Aug 31, 2012 at 10:03 PM, Gaetan Kenway <kenway at utias.utoronto.ca>wrote:
>
>> I distilled the problem down further to a simple subroutine in mgtest.F,
>> copied directly from ex8f.F
>>
>>       subroutine MGTest()
>>       implicit none
>>
>> #include "include/finclude/petsc.h"
>>
>>       KSP ksp
>>       PC pc
>>       PetscErrorCode ierr
>>       PetscInt nlevels, two
>>       two = 2
>>
>>       call KSPCreate(PETSC_COMM_WORLD,ksp,ierr)
>>       call KSPGetPC(ksp,pc,ierr)
>>       call PCSetType(pc,PCMG,ierr)
>>       call PCMGSetLevels(pc,two,PETSC_NULL_OBJECT,ierr)
>>
>>       call KSPDestroy(ksp)
>>
>
> You are certainly missing an argument (ierr) to KSPDestroy...
>

True, but the backtrace also shows that comm = 0x0 on the call to
KSPCreate(), which
leads me to believe that your petsc4py has not initialized PETSc, and
therefor not
initialized PETSC_COMM_WORLD.

   Matt

-- 
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
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