FillBoundary for corner ghost outside valid region

[ankithadas]

Dear AMReX team,

I want to fill corner ghost cells which are located outside physical boundary (at the corner of a box) overlapping a ghost cell of the adjacent box. Currently, FillBoundary will copy over values from valid cells from adjacent box and place it in the ghost cell of the current box. This works as expected and fills corner ghost cells when the boxes are strictly inside the domain. However, when the box is adjacent to a physical boundary, corner ghost cells are not copied over as these ghost cells are not overlapping valid cells.

How could I achieve this without manually filling these corner cells?

Kind regards,
Ankith

[WeiqunZhang]

You want to copy from a non-corner ghost cell of a box to a corner ghost cell of another box. This will involve MPI communication, and we do not have a function for that. It's possible to write a function for this, but I think you are better off by avoiding communication and repeating the computation locally, unless that is not possible (e.g., it involves random numbers).