Schedule groups

Implementation Boundary creates two schedule groups

ApplyBCs

and

BoundaryConditions in ApplyBCs BEFORE Boundary_ClearSelection

and schedules two functions Boundary_ApplyPhysicalBCs in BoundaryConditions and Boundary_ClearSelection in ApplyBCs. Boundary_ApplyPhysicalBCs goes through the list of all selected grid variables, and calls the registered function corresponding to the requested boundary condition on each. Boundary_ClearSelection clears the list of selected grid variables. A thorn which wishes to have boundary conditions applied simply schedules ApplyBCs at the appropriate point. Please schedule it as e.g. <MyThorn>_ApplyBCs, to make each instance of it unique. Boundary_ClearSelection ensures that each boundary condition gets executed exactly once for each selected grid variable.