problems with KSPComputeEigenvalues

[Barry Smith]

   From the manual page:

  Notes:
    The number of eigenvalues estimated depends on the size of the  
Krylov space
    generated during the KSPSolve() ; for example, with
    CG it corresponds to the number of CG iterations, for GMRES it is  
the number
    of GMRES iterations SINCE the last restart. Any extra space in r[]  
and c[]
    will be ignored.

   Likely you just have n too small by 1 or something, just make n and  
the sizes of
realpart and complex part a bit longer.

    Barry

On Jul 15, 2008, at 2:44 PM, mafunk at nmsu.edu wrote:

> Hi,
>
> i am trying to get some idea on the spectrum of my system. In order  
> to do
> that i am calling KSPSetComputeEigenvalues right before calling  
> KSPSetUp.
> Right after the call to KSPSolve i call KSPComputeEigenvalues as such:
>
> ...
>
>
>  PetscInt n = -1;
>  PetscReal * realpart;
>  PetscReal * complexpart;
>  PetscInt * neig;
>
>  KSPComputeEigenvalues(m_ksp, n, realpart, complexpart, neig);
>
> ...
>
> (I am not sure whether i have to allocate the memory for the arrays,
> however, i tried that and it made no difference).
>
> Anyway, the issue is when it enters the KSPComputeEigenvalues call.
> The error i get is:
>
> ...
>
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: Nonconforming object sizes!
> [0]PETSC ERROR: Not enough room in work space r and c for eigenvalues!
>
> ...
>
> What does that mean/how do i debug that? I.e. am i doing something  
> wrong
> in terms of usage?
>
>
> thanks
> matt
>