MPI Cart shift and MPI Graph neighbors such that they return
the first non-blank process according to the user settings.
ever, this would be equal to ignoring the ’distance’ vided by the user, or at least a redefinition of it.
FTMPI COMM MODE SHRINK
In this communicator mode, the ranks of MPI processes before and after recovery might change, as well as the size of MPI COMM WORLD does change. The appealing part of this communicator mode however is, that all functions specified in MPI-1 and MPI-2 are still valid without any further modification, since groups and communicators do not have wholes and blank processes.