Re: how to get all the singular values of the matrix?

[Yujie <recrusader@xxxxxxxxx>]

Thank you for your advice.
I have used -ksp_compute_eigenvalues_explicitly to get the eigen values. However, it is very very slow because the dimension of the matrix is about ten thousand. 
 
Yujie

On 1/14/08, Matthew Knepley <knepley@xxxxxxxxx> wrote:

You can use

http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPComputeEigenvaluesExplicitly.html

with and without a preconditioner. We have not coded the SVD
counterpart, but you can use

http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPComputeExplicitOperator.html

and then call the LAPACK yourself.

  Matt

On Jan 13, 2008 11:23 PM, Yujie < recrusader@xxxxxxxxx> wrote:
> Hi, everyone
>
> I want to select iterative methods by observing the singular values
> decompostion of the matrix. However, I don't know how to get all the
> singular values of the matrix in PETSc. I know the command
> "-ksp_monitor_singular_value" may get the max and min singular values at
> each iteration. How to get the singular values of the matrix I want to
> solve? In addition, when I use the preconditioned iterative method, how to
> get the singular values of the preconditioned iterative operator?
>
> thanks a lot.
>
> Regards,
> Yujie
>



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What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which
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