Collective Communication and Computation Operations

• MPI provides an extensive set of functions for performing commonly used collective communication operations.
  • All of the collective communication functions provided by MPI take as an argument a communicator that defines the group of processes that participate in the collective operation.
  • All the processes that belong to this communicator participate in the operation,
  • and all of them must call the collective communication function.
• Even though collective communication operations do not act like barriers,
• act like a virtual synchronization step.
• Barrier; the barrier synchronization operation is performed in MPI using the MPI_Barrier function.

  int MPI_Barrier(MPI_Comm comm)
  

• The call to MPI_Barrier returns only after all the processes in the group have called this function.