MPI_Cart_shift(3) on Linux
The text 17b2795cf2e6, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy) shipped it.
Returns the shifted source and destination ranks, given a shift direction and amount