On Thu, May 29, 2014 at 11:31 AM, Danny Lathouwers - TNW < [email protected]> wrote:
> Dear users, > > > > I have a problem where I step time and repeatedly solve a system with > differing rhs. > > At some time step petsc solver returns that initial solution is good > enough (converged reason = 2 with 0 iterations done). > > I do not expect this behaviour. I use rtol = 0.001, atol=0 and dtol =large > number. > > > > The manual seems to suggest the criterion is: rnorm < MAX (rtol * rnorm_0, > abstol) (probably based on preconditioned residual). > > How could this lead to zero iterations being done? Or is the criterion based > on rnorm/bnorm instead (which I found in some reference on the internet > concerning petsc and would explain the observed behaviour). > > Its ||b||, not ||r_0||. You can change it to get the other behavior, as detailed here http://www.mcs.anl.gov/petsc/petsc-dev/src/ksp/ksp/interface/iterativ.c.html#KSPConvergedDefault Matt > Thanks, > > Danny. > > > > > > > -- 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
