plucky (3) MPI_Ibcast.openmpi.3.gz

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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
          USE MPI
          ! or the older form: 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

   Fortran 2008 Syntax
          USE mpi_f08
          MPI_Bcast(buffer, count, datatype, root, comm, ierror)
              TYPE(*), DIMENSION(..) :: buffer
              INTEGER, INTENT(IN) :: count, root
              TYPE(MPI_Datatype), INTENT(IN) :: datatype
              TYPE(MPI_Comm), INTENT(IN) :: comm
              INTEGER, OPTIONAL, INTENT(OUT) :: ierror

          MPI_Ibcast(buffer, count, datatype, root, comm, request, ierror)
              TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buffer
              INTEGER, INTENT(IN) :: count, root
              TYPE(MPI_Datatype), INTENT(IN) :: datatype
              TYPE(MPI_Comm), INTENT(IN) :: comm
              TYPE(MPI_Request), INTENT(OUT) :: request
              INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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 o f 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  return  result  of  the  function  and
       Fortran routines in the last argument.

       Before  the  error  value  is  returned,  the current MPI error handler associated with the communication
       object (e.g., communicator, window, file) is called.  If no communication object is associated  with  the
       MPI  call,  then  the call is considered attached to MPI_COMM_SELF and will call the associated MPI error
       handler.  When  MPI_COMM_SELF  is  not  initialized   (i.e.,   before   MPI_Init/MPI_Init_thread,   after
       MPI_Finalize,  or  when using the Sessions Model exclusively) the error raises the initial error handler.
       The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF  when  using
       the  World  model,  or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/‐
       MPI_Comm_spawn_multiple.  If no other appropriate error handler has been set, then the  MPI_ERRORS_RETURN
       error  handler  is  called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
         called  on  a  communicator,  it  acts  as if MPI_Abort was called on that communicator. If called on a
         window or file, acts as if MPI_Abort was called on a communicator containing the group of processes  in
         the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler then MPI_Comm_set_errhandlerMPI_File_create_errhandler then MPI_File_set_errhandlerMPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_initMPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page for a full list of MPI error codes.

       See the Error Handling section of the MPI-3.1 standard for more information.

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                                     MPI_IBCAST(3)