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 at gmail.com> 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 at gmail.com> 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 > > > > > > -- > 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 > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20080114/1eb733be/attachment.htm>
