Broadcast

MPI_BCAST( buffer, count, datatype, root, comm )
[ INOUT buffer] starting address of buffer (choice)
[ IN count] number of entries in buffer (integer)
[ IN datatype] data type of buffer (handle)
[ IN root] rank of broadcast root (integer)
[ IN comm] communicator (handle)

int MPI_Bcast(void* buffer, int count, MPI_Datatype datatype, int root, MPI_Comm comm )

MPI_BCAST(BUFFER, COUNT, DATATYPE, ROOT, COMM, IERROR)
<type> BUFFER(*)
INTEGER COUNT, DATATYPE, ROOT, COMM, IERROR

MPI_BCAST broadcasts a message from the process with rank root to all processes of the group, itself included. It is called by all members of group using the same arguments for comm, root. On return, the contents of root's communication buffer has been copied to all processes.

General, derived datatypes are allowed for datatype. The type signature of count, datatype on any process must be equal to the type signature of count, datatype at the root. This implies that the amount of data sent must be equal to the amount received, pairwise between each process and the root. MPI_BCAST and all other data-movement collective routines make this restriction. Distinct type maps between sender and receiver are still allowed.