MPI_SEND
//MPI_Send - Performs a standard-mode blocking send.
int MPI_Send(const void *buf, int count, MPI_Datatype datatype, int dest,
int tag, MPI_Comm comm)
/*
buf
Initial address of send buffer (choice).
count
Number of elements send (nonnegative integer).
datatype
Datatype of each send buffer element (handle).
dest
Rank of destination (integer).
tag
Message tag (integer).
comm
Communicator (handle).
*/