MPI send and receive Calls
mpi_send(buf,count,datatype,dest,tag,comm,ierr)
mpi_recv(buf,count,datatype,dest,tag,comm,stat,ierr)
buff data to be send/recv
count number of items to be send; size of buf for recv
datatype type of data items to send/recv (MPI_INTEGER, MPI_FLOAT, MPI_DOUBLE_PRECISION, etc.)
dest id of the pear process (MPI_ANY_SOURCE)
tag integer mark of the message (MPI_ANY_TAG)
comm communication handle (MPI_COMM_WORLD)
stat status of the message of MPI_STATUS type; in Fortran INTEGER stat(MPI_STATUS_SIZE) call mpi_get_count(stat,MPI_REAL,nitems) where nitems can be <= count
if(ierr.ne.MPI_SUCCESS) call abort()