MPI_BARRIER(comm)
[ IN comm] communicator (handle)
void MPI::Comm::Barrier() const = 0
For MPI-2, comm may be an intercommunicator or an intracommunicator. If comm is an intercommunicator, the barrier is performed across all processes in the intercommunicator. In this case, all processes in the local group of the intercommunicator may exit the barrier when all of the processes in the remote group have entered the barrier.
MPI_SCAN(sendbuf, recvbuf, count, datatype, op, comm)
[ IN sendbuf] starting address of send buffer (choice)
[ OUT recvbuf] starting address of receive buffer (choice)
[ IN count] number of elements in input buffer (integer)
[ IN datatype] data type of elements of input buffer (handle)
[ IN op] operation (handle)
[ IN comm] communicator (handle)
The ``in place'' option for intracommunicators is specified by passing MPI_IN_PLACE in the sendbuf argument. In this case, the input data is taken from the receive buffer, and replaced by the output data.
This operation is illegal for intercommunicators.