NAME

       MPI_Bcast,  MPI_Ibcast - Broadcasts a message from the process with rank root to all other
       processes of the group.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Bcast(void *buffer, int count, MPI_Datatype datatype,
            int root, MPI_Comm comm)

       int MPI_Ibcast(void *buffer, int count, MPI_Datatype datatype,
            int root, MPI_Comm comm, MPI_Request *request)

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_BCAST(BUFFER, COUNT, DATATYPE, ROOT, COMM, IERROR)
            <type>    BUFFER(*)
            INTEGER   COUNT, DATATYPE, ROOT, COMM, IERROR

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

C++ Syntax

       #include <mpi.h>
       void MPI::Comm::Bcast(void* buffer, int count,
            const MPI::Datatype& datatype, int root) const = 0

INPUT/OUTPUT PARAMETERS

       buffer    Starting address of buffer (choice).

       count     Number of entries in buffer (integer).

       datatype  Data type of buffer (handle).

       root      Rank of broadcast root (integer).

       comm      Communicator (handle).

OUTPUT PARAMETERS

       request   Request (handle, non-blocking only).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       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.

       Example: Broadcast 100 ints from process 0 to every process in the group.
           MPI_Comm comm;
           int array[100];
           int root=0;
           ...
           MPI_Bcast( array, 100, MPI_INT, root, comm);

       As in many of our sample code fragments, we assume that some of  the  variables  (such  as
       comm in the example above) have been assigned appropriate values.

WHEN COMMUNICATOR IS AN INTER-COMMUNICATOR

       When  the  communicator  is  an  inter-communicator,  the  root process in the first group
       broadcasts data to all the processes in the second group.  The  first  group  defines  the
       root  process.   That  process  uses  MPI_ROOT  as  the  value  of its root argument.  The
       remaining processes use MPI_PROC_NULL as the value of their root argument.  All  processes
       in  the  second group use the rank of that root process in the first group as the value of
       their root argument.   The receive buffer arguments of the processes in the  second  group
       must be consistent with the send buffer argument of the root process in the first group.

NOTES

       This function does not support the in-place option.

ERRORS

       Almost all MPI routines return an error value; C routines as the value of the function and
       Fortran routines in the last argument. C++ functions do not return errors. If the  default
       error  handler  is  set  to  MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception
       mechanism will be used to throw an MPI::Exception object.

       Before the error value is returned, the current MPI error handler is called.  By  default,
       this  error  handler aborts the MPI job, except for I/O function errors. The error handler
       may   be   changed   with   MPI_Comm_set_errhandler;   the   predefined   error    handler
       MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not
       guarantee that an MPI program can continue past an error.