There are special cases, the explanation can be rather lengthy. I instead point you to the actual code:
http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/src/ksp/ksp/interface/iterativ.c.html#KSPDefaultConverged Matt On Thu, Apr 3, 2008 at 6:34 AM, Stephen R Ball <Stephen.R.Ball at awe.co.uk> wrote: > Hi > > I am trying to determine the default convergence test used by PETSc. > Your pdf user's guide states the default test is based on the decrease > of the residual norm relative to the right-hand-side while your html > documentation for KSPDefaultConverged() seems to imply that the default > test is based on the decrease of the residual norm relative to the > initial residual norm. Can you tell me which is actually the default? > > Regards > > Stephen > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
