The two additional functions introduced in this section can be used to implement all other topology functions. In general they will not be called by the user directly, unless he or she is creating additional virtual topology capability other than that provided by MPI.
| MPI_CART_MAP(comm, ndims, dims, periods, newrank) | |
| IN comm | input communicator (handle) |
| IN ndims | number of dimensions of Cartesian structure (integer) |
| IN dims | integer array of size ndims specifying the number of processes in each coordinate direction |
| IN periods | logical array of size ndims specifying the periodicity specification in each coordinate direction |
| OUT newrank | reordered rank of the calling process; MPI_UNDEFINED if calling process does not belong to grid (integer) |
int MPI_Cart_map(MPI_Comm comm, int ndims, int *dims, int *periods, int *newrank)
MPI_CART_MAP(COMM, NDIMS, DIMS, PERIODS, NEWRANK, IERROR)
The function MPI_CART_CREATE(comm, ndims, dims,
periods, reorder, comm_cart), with reorder = true can be implemented by
calling
MPI_CART_MAP(comm, ndims, dims, periods, newrank), then calling
The function MPI_CART_SUB(comm, remain_dims, comm_new) can be
implemented by a call to MPI_COMM_SPLIT(comm, color, key, comm_new),
using a single number encoding of the lost dimensions as color and a
single number encoding of the preserved dimensions as key.
All other Cartesian topology functions can be implemented locally, using
the topology information that is cached with the communicator.
( End of advice to implementors.)
int MPI_Graph_map(MPI_Comm comm, int nnodes, int *index, int *edges, int *newrank)
MPI_GRAPH_MAP(COMM, NNODES, INDEX, EDGES, NEWRANK, IERROR)
The function MPI_GRAPH_CREATE(comm, nnodes, index, edges,
reorder, comm_graph),
with reorder = true can be implemented by calling
MPI_GRAPH_MAP(comm, nnodes, index, edges, newrank),
then calling
All other graph topology functions can be implemented locally, using the
topology information that is cached with the communicator.
( End of advice to implementors.)
INTEGER COMM, NDIMS, DIMS(*), NEWRANK, IERROR
LOGICAL PERIODS(*)
{ int MPI::Cartcomm::Map(int ndims, const int dims[], const bool periods[]) const (binding deprecated, see Section Deprecated since MPI-2.2
) }
MPI_CART_MAP
computes an ``optimal'' placement for the calling process on the
physical machine. A possible implementation of this function is to always
return the rank of the calling process, that is, not to perform any reordering.
Advice
to implementors.
MPI_COMM_SPLIT(comm, color, key, comm_cart), with
color = 0 if newrank 
MPI_UNDEFINED, color = MPI_UNDEFINED otherwise,
and key = newrank.
The corresponding new function for general graph structures is as follows.
MPI_GRAPH_MAP(comm, nnodes, index, edges, newrank) IN comm input communicator (handle) IN nnodes number of graph nodes (integer) IN index integer array specifying the graph structure, see
MPI_GRAPH_CREATE IN edges integer array specifying the graph structure OUT newrank reordered rank of the calling process; MPI_UNDEFINED if the calling process does not belong to graph (integer)
INTEGER COMM, NNODES, INDEX(*), EDGES(*), NEWRANK, IERROR
{ int MPI::Graphcomm::Map(int nnodes, const int index[], const int edges[]) const (binding deprecated, see Section Deprecated since MPI-2.2
) }
Advice
to implementors.
MPI_COMM_SPLIT(comm, color, key, comm_graph), with color = 0
if newrank 
MPI_UNDEFINED, color = MPI_UNDEFINED
otherwise, and key = newrank.
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