The Periodic BC solution given by mikael-mortensen in the post Is it possible to specify more than one periodic boundary condition? has been referred by many. But one question remains unresolved: Why do we have the last else conditions mapping H to somewhere outside the mesh domain.
However it is essential because otherwise it gives the following error:
*** Error: Unable to periodic boundary mapping.
*** Reason: Need to set coordinate 0 in sub_domain.map.
*** Where: This error was encountered inside PeriodicBoundaryComputation.cpp.
To this end, it would be very help if someone or mikael-mortensen himself can resolve the issue, since many like me might have the same confusion.
Thanks in advance.
Sincerely,
Shankha