224 lines
6.6 KiB
Groff
224 lines
6.6 KiB
Groff
.\" Man page generated from reStructuredText.
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.TH "MPI_PACK" "3" "Feb 14, 2025" "" "Open MPI"
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.in \\n[rst2man-indent\\n[rst2man-indent-level]]u
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..
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.sp
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\fI\%MPI_Pack\fP — Packs data of a given datatype into contiguous memory.
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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_Pack(const void *inbuf, int incount, MPI_Datatype datatype,
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void *outbuf, int outsize, int *position, MPI_Comm 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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.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_PACK(INBUF, INCOUNT, DATATYPE, OUTBUF,OUTSIZE, POSITION,
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COMM, IERROR)
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<type> INBUF(*), OUTBUF(*)
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INTEGER INCOUNT, DATATYPE, OUTSIZE, POSITION, COMM, 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_Pack(inbuf, incount, datatype, outbuf, outsize, position, comm, ierror)
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TYPE(*), DIMENSION(..), INTENT(IN) :: inbuf
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TYPE(*), DIMENSION(..) :: outbuf
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INTEGER, INTENT(IN) :: incount, outsize
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TYPE(MPI_Datatype), INTENT(IN) :: datatype
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INTEGER, INTENT(INOUT) :: position
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TYPE(MPI_Comm), INTENT(IN) :: comm
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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 PARAMETERS
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.INDENT 0.0
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.IP \(bu 2
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\fBinbuf\fP: Input buffer start (choice).
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.IP \(bu 2
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\fBincount\fP: Number of input data items (integer).
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.IP \(bu 2
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\fBdatatype\fP: Datatype of each input data item (handle).
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.IP \(bu 2
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\fBoutsize\fP: Output buffer size, in bytes (integer).
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.IP \(bu 2
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\fBcomm\fP: Communicator for packed message (handle).
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.UNINDENT
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.SH INPUT/OUTPUT PARAMETER
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.INDENT 0.0
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.IP \(bu 2
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\fBposition\fP: Current position in buffer, in bytes (integer).
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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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\fBoutbuf\fP: Output buffer start (choice).
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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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Packs the message in the send buffer specified by \fIinbuf\fP, \fIincount\fP,
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\fIdatatype\fP into the buffer space specified by \fIoutbuf\fP and \fIoutsize\fP\&.
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The input buffer can be any communication buffer allowed in \fI\%MPI_Send\fP\&.
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The output buffer is a contiguous storage area containing \fIoutsize\fP
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bytes, starting at the address \fIoutbuf\fP (length is counted in bytes, not
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elements, as if it were a communication buffer for a message of type
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MPI_Packed).
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.sp
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The input value of \fIposition\fP is the first location in the output buffer
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to be used for packing. \fIposition\fP is incremented by the size of the
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packed message, and the output value of \fIposition\fP is the first location
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in the output buffer following the locations occupied by the packed
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message. The \fIcomm\fP argument is the communicator that will be
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subsequently used for sending the packed message.
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.sp
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\fBExample:\fP An example using \fI\%MPI_Pack\fP:
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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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int myrank, position, i, j, a[2];
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char buff[1000];
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// ...
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MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
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if (myrank == 0) {
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/* SENDER CODE */
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position = 0;
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MPI_Pack(&i, 1, MPI_INT, buff, 1000, &position, MPI_COMM_WORLD);
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MPI_Pack(&j, 1, MPI_INT, buff, 1000, &position, MPI_COMM_WORLD);
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MPI_Send(buff, position, MPI_PACKED, 1, 0, MPI_COMM_WORLD);
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} else {
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/* RECEIVER CODE */
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MPI_Recv(a, 2, MPI_INT, 0, 0, MPI_COMM_WORLD);
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}
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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 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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.sp
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\fBSEE ALSO:\fP
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.INDENT 0.0
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.INDENT 3.5
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.INDENT 0.0
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.IP \(bu 2
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\fI\%MPI_Unpack\fP
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.IP \(bu 2
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\fI\%MPI_Pack_size\fP
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.UNINDENT
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.UNINDENT
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.UNINDENT
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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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