Thank you for your advice.<br>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. <br> <br>Yujie<br><br><div><span class="gmail_quote">
On 1/14/08, <b class="gmail_sendername">Matthew Knepley</b> <<a href="mailto:knepley@gmail.com">knepley@gmail.com</a>> wrote:</span><blockquote class="gmail_quote" style="margin-top: 0; margin-right: 0; margin-bottom: 0; margin-left: 0; margin-left: 0.80ex; border-left-color: #cccccc; border-left-width: 1px; border-left-style: solid; padding-left: 1ex">
You can use<br><br><a href="http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPComputeEigenvaluesExplicitly.html">http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPComputeEigenvaluesExplicitly.html
</a><br><br>with and without a preconditioner. We have not coded the SVD<br>counterpart, but you can use<br><br><a href="http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPComputeExplicitOperator.html">
http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPComputeExplicitOperator.html</a><br><br>and then call the LAPACK yourself.<br><br> Matt<br><br>On Jan 13, 2008 11:23 PM, Yujie <
<a href="mailto:recrusader@gmail.com">recrusader@gmail.com</a>> wrote:<br>> Hi, everyone<br>><br>> I want to select iterative methods by observing the singular values<br>> decompostion of the matrix. However, I don't know how to get all the
<br>> singular values of the matrix in PETSc. I know the command<br>> "-ksp_monitor_singular_value" may get the max and min singular values at<br>> each iteration. How to get the singular values of the matrix I want to
<br>> solve? In addition, when I use the preconditioned iterative method, how to<br>> get the singular values of the preconditioned iterative operator?<br>><br>> thanks a lot.<br>><br>> Regards,<br>> Yujie
<br>><br><br><br><br>--<br>What most experimenters take for granted before they begin their<br>experiments is infinitely more interesting than any results to which<br>their experiments lead.<br>-- Norbert Wiener<br><br>
</blockquote></div><br>