Thanks Matt for your quick response. I got to believe that it was the relative ratio of the residual from the following petsc links:
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPSetTolerances.html and http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPDefaultConverged.html#KSPDefaultConverged Perhaps these pages are outdated? Cheers, Danny.
