STEPHANE TCHOUANMO wrote: > Is there a way to get the conditionning of my Jacobian matrices? like a > command when running my exectable (-ksp_.. or -snes_.. or -pc_..)
I use -ksp_monitor_singular_value estimate at every Krylov iteration, only works with GMRES and CG -ksp_compute_eigenvalues estimate of a few eigenvalues from the iteration (GMRES and CG) -ksp_compute_eigenvalues_explicitly sometimes useful for very small systems, e.g. to find the size of a null space while debugging -ksp_plot_eigenvalues_explicitly again, only for very small problems. Note that these eigenvalues and singular values are not reliable for eigen-analysis, they are only intended to help understand why iterative methods are working a certain way. If you care about accurate eigen/singular values, use SLEPc. I noticed a few weeks ago that -ksp_compute_singularvalues didn't work as advertised. A few lines needed to be added to KSPSolve(), as for -ksp_compute_eigenvalues. I usually use -ksp_monitor_singular_value instead, so it hadn't bothered me, but it's now in petsc-dev: http://petsc.cs.iit.edu/petsc/petsc-dev/rev/3180aa7f49b4 Jed -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 260 bytes Desc: OpenPGP digital signature URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20090716/c35e0631/attachment.pgp>
