MPI_Graph_neighbors_count(3) on Linux
The text 1271d16ccf42, as Debian 13 (Trixie), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy) shipped it.
Returns the number of neighbors of a node associated with a graph topology