Performance degradation after upgrade to 3.0.0

[Matthew Knepley]

In order to determine what is happening you first should:

  1) Confirm that the solver setup is identical using -ksp_view for
both versions

  2) Determine that the matrices are identical. Output both matrices using
      MatView() with a PetscBinaryViewer. You can diff the files, and
you can also
      solver both matrices using KSP ex10.

  3) Look at the residuals using -ksp_monitor. If they are different, something
      else has changed.

  Matt

On Sun, Feb 1, 2009 at 6:32 AM, Billy Araújo <billy at dem.uminho.pt> wrote:
>
> Hi,
>
> I have also verified that there has been a degradation of performance using
> the new 3.0 version:
>
> This is my function calling PETSc:
>
>   KSP ksp;
>   PC pc;
>
>   KSPCreate (PETSC_COMM_WORLD, &ksp);
>
>   KSPSetOperators (ksp, *A, *A, DIFFERENT_NONZERO_PATTERN);
>
>   KSPSetType (ksp, KSPFGMRES);
>
>   KSPGetPC (ksp, &pc);
>
>   PCSetType (pc, PrecondProc);
>
>   KSPSetInitialGuessNonzero (ksp, PETSC_TRUE);
>
>   KSPSetTolerances (ksp, 1E-50, maxtol, PETSC_DEFAULT, maxiter);
>
>   KSPSetFromOptions (ksp);
>
>   KSPSolve (ksp, *b, *x);
>
>   KSPGetIterationNumber (ksp, iter);
>
>   KSPGetResidualNorm (ksp, res);
>
>   KSPDestroy (ksp);
>
>
> with previous version 2.3.3-p6:
>
> Number of iterations: 42 Residual: +7.073781E-13 Time: +8.615024E-03
>
> now:
>
> Number of iterations: 500 Residual: +2.746161E-05 Time: +1.026870E-01
>
> It is reaching maximum number of iterations. The only thing I changed was:
>
> MatSetOption (*A, MAT_SYMMETRIC);
>  to
> MatSetOption (*A, MAT_SYMMETRIC, PETSC_TRUE);
>
> I think I didn't change anything else.
>
>
> Regards,
>
> Billy.
>



-- 
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