This routine allows the user to map processes to the process grid in an arbitrary manner.
holds the process number of the process to be placed in
of the process grid. On most distributed systems, this process number is a machine defined number between 0 ...
-1. For PVM, these node numbers are the PVM TIDS (Task IDs). The
routine is intended for an experienced user. The
routine is much simpler.
simply performs a
where the first
nprow * npcol
processes are mapped into the current grid in a row-major natural ordering. If you are an experienced user,
allows you to take advantage of your system's actual layout. That is, you can map nodes that are physically connected to be neighbors in the BLACS grid, etc. The
routine also opens the way for multigridding
: you can separate your nodes into arbitrary grids, join them together at some later date, and then re-split them into new grids.
also provides the ability to make arbitrary grids or subgrids (for example, a "nearest neighbor" grid), which can greatly facilitate operations among processes that do not fall on a row or column of the main process grid.