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MPI: the Message Passing
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Communicators
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Getting Information
MPI_Comm_size
function
number of processes
MPI_Comm_rank
function
label of the calling process
The calling sequences of these routines are as follows:
int MPI_Comm_size(MPI_Comm comm, int *size) int MPI_Comm_rank(MPI_Comm comm, int *rank)
The function MPI_Comm_size returns in the variable size the number of processes that belong to the communicator
comm
.
Every process that belongs to a communicator is uniquely identified by its
rank
.
The rank of a process is an integer that ranges from zero up to the size of the communicator minus one.
Up on return, the variable
rank
stores the rank of the process.