Dear all, I am trying to use Boomer AMG of hypre + GMRES for my nonlinear problem, which is solved by MUMPS or GMRES +ILU previously. However AMG does not convergence. The -ksp_monitor shows that there are huge residual during inner GMRES iteration, as large as 1e30. I only change PC from ILU to boomeramg. Can anyone tell me what's wrong with it? Gong Ding