On Apr 14, 2013, at 5:23 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> 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 See also: http://www.mcs.anl.gov/petsc/documentation/faq.html#differentiterations and http://www.mcs.anl.gov/petsc/documentation/faq.html#kspdiverged
