Environment Routines
•There are a number of important routines for monitoring and controlling an MPI environment .
•MPI_INIT(ierr),MPI_Init(&argc,&argv)
•   This initialises the MPI environment e.g setting up node id..
•MPI_INITIALIZED(flag,ierr)
•    This tells whether MPI_INIT has been called or not.
•MPI_COMM_SIZE(comm,size.ierr)
•   This returns the total number of processors in the communicator ‘comm’
•MPI_COMM_RANK(comm,rank,ierr)
•    This returns the rank of the processor on which it is called.