231 lines
7.2 KiB
Groff
231 lines
7.2 KiB
Groff
.\" Man page generated from reStructuredText.
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.TH "MPI_BCAST_INIT" "3" "Feb 14, 2025" "" "Open MPI"
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..
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.INDENT 0.0
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.INDENT 3.5
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.UNINDENT
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.UNINDENT
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.sp
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\fI\%MPI_Bcast\fP, \fI\%MPI_Ibcast\fP \- Broadcasts a message from the process
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with rank \fIroot\fP to all other processes of the group.
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.SH SYNTAX
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.SS C Syntax
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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#include <mpi.h>
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int MPI_Bcast(void *buffer, int count, MPI_Datatype datatype,
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int root, MPI_Comm comm)
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int MPI_Ibcast(void *buffer, int count, MPI_Datatype datatype,
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int root, MPI_Comm comm, MPI_Request *request)
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SS Fortran Syntax
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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USE MPI
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! or the older form: INCLUDE \(aqmpif.h\(aq
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MPI_BCAST(BUFFER, COUNT, DATATYPE, ROOT, COMM, IERROR)
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<type> BUFFER(*)
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INTEGER COUNT, DATATYPE, ROOT, COMM, IERROR
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MPI_IBCAST(BUFFER, COUNT, DATATYPE, ROOT, COMM, REQUEST, IERROR)
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<type> BUFFER(*)
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INTEGER COUNT, DATATYPE, ROOT, COMM, REQUEST, IERROR
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SS Fortran 2008 Syntax
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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USE mpi_f08
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MPI_Bcast(buffer, count, datatype, root, comm, ierror)
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TYPE(*), DIMENSION(..) :: buffer
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INTEGER, INTENT(IN) :: count, root
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TYPE(MPI_Datatype), INTENT(IN) :: datatype
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TYPE(MPI_Comm), INTENT(IN) :: comm
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INTEGER, OPTIONAL, INTENT(OUT) :: ierror
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MPI_Ibcast(buffer, count, datatype, root, comm, request, ierror)
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TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buffer
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INTEGER, INTENT(IN) :: count, root
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TYPE(MPI_Datatype), INTENT(IN) :: datatype
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TYPE(MPI_Comm), INTENT(IN) :: comm
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TYPE(MPI_Request), INTENT(OUT) :: request
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INTEGER, OPTIONAL, INTENT(OUT) :: ierror
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SH INPUT/OUTPUT PARAMETERS
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.INDENT 0.0
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.IP \(bu 2
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\fBbuffer\fP: Starting address of buffer (choice).
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.IP \(bu 2
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\fBcount\fP: Number of entries in buffer (integer).
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.IP \(bu 2
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\fBdatatype\fP: Data type of buffer (handle).
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.IP \(bu 2
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\fBroot\fP: Rank of broadcast root (integer).
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.IP \(bu 2
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\fBcomm\fP: Communicator (handle).
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.UNINDENT
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.SH OUTPUT PARAMETERS
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.INDENT 0.0
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.IP \(bu 2
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\fBrequest\fP: Request (handle, non\-blocking only).
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.IP \(bu 2
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\fBierror\fP: Fortran only: Error status (integer).
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.UNINDENT
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.SH DESCRIPTION
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.sp
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\fI\%MPI_Bcast\fP broadcasts a message from the process with rank root to
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all processes of the group, itself included. It is called by all members
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of group using the same arguments for \fBcomm\fP, \fBroot\fP\&. On return, the
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contents of root’s communication buffer has been copied to all
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processes.
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.sp
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General, derived datatypes are allowed for datatype. The type signature
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of count, datatype on any process must be equal to the type signature o
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f count, datatype at the root. This implies that the amount of data sent
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must be equal to the amount received, pairwise between each process and
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the root. \fI\%MPI_Bcast\fP and all other data\-movement collective routines
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make this restriction. Distinct type maps between sender and receiver
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are still allowed.
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.sp
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\fBExample:\fP Broadcast 100 ints from process 0 to every process in the
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group.
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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MPI_Comm comm;
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int array[100];
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int root=0;
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//...
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MPI_Bcast( array, 100, MPI_INT, root, comm);
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.sp
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As in many of our sample code fragments, we assume that some of the
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variables (such as comm in the example above) have been assigned
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appropriate values.
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.SH WHEN COMMUNICATOR IS AN INTER-COMMUNICATOR
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.sp
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When the communicator is an inter\-communicator, the root process in the
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first group broadcasts data to all the processes in the second group.
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The first group defines the root process. That process uses MPI_ROOT
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as the value of its \fBroot\fP argument. The remaining processes use
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\fBMPI_PROC_NULL\fP as the value of their \fBroot\fP argument. All processes
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in the second group use the rank of that root process in the first group
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as the value of their \fBroot\fP argument. The receive buffer arguments of
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the processes in the second group must be consistent with the send
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buffer argument of the root process in the first group.
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.SH NOTES
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.sp
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This function does not support the in\-place option.
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.SH ERRORS
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.sp
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Almost all MPI routines return an error value; C routines as the return result
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of the function and Fortran routines in the last argument.
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.sp
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Before the error value is returned, the current MPI error handler associated
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with the communication object (e.g., communicator, window, file) is called.
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If no communication object is associated with the MPI call, then the call is
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considered attached to MPI_COMM_SELF and will call the associated MPI error
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handler. When MPI_COMM_SELF is not initialized (i.e., before
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\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
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Model exclusively) the error raises the initial error handler. The initial
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error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
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MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
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argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
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If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
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error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error
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handler is called for all other MPI functions.
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.sp
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Open MPI includes three predefined error handlers that can be used:
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.INDENT 0.0
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.IP \(bu 2
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\fBMPI_ERRORS_ARE_FATAL\fP
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Causes the program to abort all connected MPI processes.
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.IP \(bu 2
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\fBMPI_ERRORS_ABORT\fP
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An error handler that can be invoked on a communicator,
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window, file, or session. When called on a communicator, it
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acts as if \fI\%MPI_Abort\fP was called on that communicator. If
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called on a window or file, acts as if \fI\%MPI_Abort\fP was called
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on a communicator containing the group of processes in the
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corresponding window or file. If called on a session,
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aborts only the local process.
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.IP \(bu 2
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\fBMPI_ERRORS_RETURN\fP
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Returns an error code to the application.
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.UNINDENT
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.sp
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MPI applications can also implement their own error handlers by calling:
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.INDENT 0.0
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.IP \(bu 2
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\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
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.IP \(bu 2
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\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
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.IP \(bu 2
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\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
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.IP \(bu 2
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\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
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.UNINDENT
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.sp
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Note that MPI does not guarantee that an MPI program can continue past
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an error.
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.sp
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See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
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.sp
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See the Error Handling section of the MPI\-3.1 standard for
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more information.
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.SH COPYRIGHT
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2003-2025, The Open MPI Community
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.\" Generated by docutils manpage writer.
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.
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