BLACS -- Advanced Topics
The BLACS context is the BLACS mechanism for partitioning communication space. A defining property of a context is that a message in a context cannot be sent or received in another context. The BLACS context includes the definition of a grid, and the process coordinates within it.
create arbitrary groups of processes,
create multiple overlapping and/or disjoint grids,
isolate each process grid so that grids do not interfere with each other.
BLACS context MPI communicator