The basic outline of an MPI program follows these general steps:

1. Initialize communications
2. Communicate to share data between processes
3. Exit in a "clean" fashion from the message-passing system when done communicating

A programmer new to MPI can usually make do with only six functions. These functions, illustrated and discussed in our sample program, are:

Initialize communications

MPI_INIT

initializes the MPI environment

MPI_COMM_SIZE

returns the number of processes

MPI_COMM_RANK

returns this process's number (rank)

Communicate to share data between processes

MPI_SEND

sends a message

MPI_RECV

receives a message

Exit from the message-passing system

MPI_FINALIZE

leave the MPI environment