Matt, Barry,

Should I do any particular trick to solve block matrices in ksp?

I am doing a silly 3x3 cavity test case and I am struggling to converge using CG+bjacobi. It might be I have an error in the matrix, but just to be sure I am not missing something fundamental in the setup.

This is my log that shows how norm residual is far to be happy:

10000 KSP unpreconditioned resid norm 2.273088479279e+03 true resid norm 2.273088479279e+03 ||r(i)||/||b|| 6.561841227018e+02
Reason = -3
ERROR: KSP has not converged. Simulations stopped.
[0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
[0]PETSC ERROR: KSPSolve has not converged, reason DIVERGED_ITS

Thank you