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In many applications the processes are arranged with a particular topology,
such as a two- or three-dimensional grid.
MPI provides support for general application topologies that are
specified by a graph in which processes that communicate a significant amount
are connected by an arc. If the application topology is an n-dimensional
Cartesian
grid then this generality is not needed, so as a convenience MPI provides
explicit support for such topologies. For a Cartesian grid, periodic or
nonperiodic boundary conditions may apply in any specified grid dimension.
In MPI, a group either has a Cartesian or graph topology, or no topology.
In addition to providing routines for
translating between process rank and location in the topology, MPI also:
-
allows knowledge of the application topology to be exploited in order to
efficiently assign processes to physical processors,
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provides a routine for partitioning a Cartesian grid into
hyperplane groups by removing a specified set of dimensions,
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provides support for shifting data along a specified dimension of a
Cartesian grid.
By dividing a Cartesian grid into hyperplane groups it is possible to
perform collective communication operations within these groups. In particular,
if all but one dimension is removed a set of one-dimensional subgroups is
formed, and it is possible, for example, to perform a multicast in the
corresponding direction.
top500@rz.uni-mannheim.de
Tue May 28 14:38:25 PST 1996