[petsc-dev] KSP monitor

[Nathan Collier]

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/examples/tutorials/ex9.c.html

where I get the current state of the solution vector using

KSPBuildSolution(kps,PETSC_NULL,&U)

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)
nathaniel.collier at gmail.com
nathaniel.collier at kaust.edu.sa