On Apr 26, 2011, at 6:50 AM, Nathan Collier wrote:

Good day,

I am solving a linear problem using finite elements with PETSC and I want to look at the H1 norm of my true error as a function of KSP iterations. I registered my own monitor function with KSP which looks something like the last function in this example:

http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-dev/src/ksp/ksp/exampl...

where I get the current state of the solution vector using

KSPBuildSolution(kps,PETSC_NULL,&U)

Try using KSPBuildSolution(ksp,work,0); where you create the work vector in your monitor routine. There could be a bug in the usuage you are using. Let us know if this works. Barry

Then I use U to compute the H1 norm. As per the documentation I do not Destroy U after. When I have this monitor function registered, my H1 norm diverges while the KSP residual converges. Also, I compute the final H1 norm (outside of the monitor) and it is divergent, which matches the last iteration. If I remove my monitor function, things work well.

What am I screwing up? How can I access the current solution vector in a KSP monitor? Do I need to use a vector that I create from a DA since my FEM matrix assembly is based in DAs?

Thanks, NAte

-- Nathan Collier Postdoctoral Researcher King Abdullah University of Science and Technology (KAUST) [email protected] [email protected]