[petsc-users] Seq vs MPI convergence

[Jed Brown]

Hugo Gagnon <opensource.petsc at user.fastmail.fm> writes:

> Hi,
>
> I have a problem that converges fine in sequential mode but diverges
> in MPI (other problems seem to converge fine for both modes).  I am no
> expert in parallel solvers but, is this something I should expect?
> I'm using BiCGSTAB with BJACOBI ILU(3).  Perhaps I'm overseeing some
> parameters that could improve my convergences?

The most common problem is that you assemble a different operator in
parallel.  So check that and check that you get the same answer when
using redundant solves.

  -pc_type redundant -redundant_pc_type ilu