MPI Functions - An Overview of the Syntax

Function	Syntax
MPI_Init	int MPI_Init(int* argc, char*** argv);
MPI_Finalize	int MPI_Finalize(void);
MPI_Comm_size	int MPI_Comm_size(MPI_Comm com, int* size);
MPI_Comm_rank	int MPI_Comm_rank(MPI_Comm com, int* rank);
MPI_Send	int MPI_Send(void* data, int count, MPI_Datatype datatype, int destination, int tag, MPI_Comm com);
MPI_Recv	int MPI_Recv(void* data, int count, MPI_Datatype datatype, int source, int tag, MPI_Comm com, MPI_Status* status);
MPI_Reduce	int MPI_Reduce(void* sendbuf, void* recvbuf, int count, MPI_Datatype datatype, MPI_Op op, int root, MPI_Comm comm);
MPI_Bcast	int MPI_Bcast(void *buffer, int count, MPI_Datatype datatype, int root,MPI_Comm comm);

Note: MPI_COMM_WORLD is not a function but a predefined constant used in most of these functions as the comm parameter.

MPI_COMM_WORLD	MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);

Parameters:

• argc, argv: Command line arguments (passed by reference)
• com: MPI communicator (typically MPI_COMM_WORLD)
• size: Pointer to store number of processes
• rank: Pointer to store process rank
• data: Pointer to data buffer
• count: Number of elements to send/receive
• datatype: MPI data type (e.g., MPI_INT, MPI_CHAR)
• destination/source: Target/source process rank
• tag: Message tag for identification
• status: Status object for receive operations

All functions return an integer status code indicating success or failure. on operations: MPI_SUM, MPI_MAX, MPI_MIN, MPI_PROD

Quick Reference:

• Single values: use &
• Arrays: no & (e.g., MPI_Send(array, 10, MPI_INT, ...))
• Common datatypes: MPI_INT, MPI_DOUBLE, MPI_FLOAT, MPI_CHAR
• Common operations: MPI_SUM, MPI_MAX, MPI_MIN, MPI_PROD