Dear all, I try to extract boundary region by running: FieldConvert -m extract:fldtoboundary=1 cylinder1_Spherigon.xml cylinder1_Spherigon_5.chk cylinder1_Spherigon_5-boundary.chk Here my cylinder1_Spherigob_5.chk is a folder which contains: [image: Screen Shot 2019-06-05 at 6.06.53 PM.png] This is due to we use mpirun command to do simulation. However, we get the errors when running the above command: Fatal : Level 0 assertion violation Variable index out of range. libc++abi.dylib: terminating with uncaught exception of type ErrorUtil::NekError: Level 0 assertion violation Variable index out of range. Abort trap: 6 May I know how can I deal with such .chk file? Thank you very much! Best, Shan