Starting and Terminating the MPI Library

• MPI_Init is called prior to any calls to other MPI routines.
  • Its purpose is to initialize the mpi environment.
  • Calling MPI_Init more than once during the execution of a program will lead to an error.
• MPI_Finalize is called at the end of the computation.
  • It performs various clean-up tasks to terminate the MPI environment.
  • No MPI calls may be performed after MPI_Finalize has been called, not even MPI_Init.
• Upon successful execution, MPI_Init and MPI_Finalize return
  MPI_SUCCESS; otherwise they return an implementation-defined error code.