231 lines
7.9 KiB
Groff
231 lines
7.9 KiB
Groff
.\" Man page generated from reStructuredText.
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.TH "MPI_SENDRECV" "3" "Feb 14, 2025" "" "Open MPI"
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.sp
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\fI\%MPI_Sendrecv\fP — Sends and receives a message.
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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_Sendrecv(const void *sendbuf, int sendcount, MPI_Datatype sendtype,
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int dest, int sendtag, void *recvbuf, int recvcount,
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MPI_Datatype recvtype, int source, int recvtag,
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MPI_Comm comm, MPI_Status *status)
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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_SENDRECV(SENDBUF, SENDCOUNT, SENDTYPE, DEST, SENDTAG,
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RECVBUF, RECVCOUNT, RECVTYPE, SOURCE, RECVTAG, COMM,
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STATUS, IERROR)
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<type> SENDBUF(*), RECVBUF(*)
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INTEGER SENDCOUNT, SENDTYPE, DEST, SENDTAG
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INTEGER RECVCOUNT, RECVTYPE, SOURCE, RECVTAG, COMM
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INTEGER STATUS(MPI_STATUS_SIZE), 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_Sendrecv(sendbuf, sendcount, sendtype, dest, sendtag, recvbuf,
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recvcount, recvtype, source, recvtag, comm, status, ierror)
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TYPE(*), DIMENSION(..), INTENT(IN) :: sendbuf
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TYPE(*), DIMENSION(..) :: recvbuf
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INTEGER, INTENT(IN) :: sendcount, dest, sendtag, recvcount, source,
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recvtag
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TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
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TYPE(MPI_Comm), INTENT(IN) :: comm
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TYPE(MPI_Status) :: status
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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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\fBsendbuf\fP: Initial address of send buffer (choice).
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.IP \(bu 2
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\fBsendcount\fP: Number of elements to send (integer).
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.IP \(bu 2
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\fBsendtype\fP: Type of elements in send buffer (handle).
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.IP \(bu 2
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\fBdest\fP: Rank of destination (integer).
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.IP \(bu 2
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\fBsendtag\fP: Send tag (integer).
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.IP \(bu 2
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\fBrecvcount\fP: Maximum number of elements to receive (integer).
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.IP \(bu 2
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\fBrecvtype\fP: Type of elements in receive buffer (handle).
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.IP \(bu 2
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\fBsource\fP: Rank of source (integer).
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.IP \(bu 2
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\fBrecvtag\fP: Receive tag (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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\fBrecvbuf\fP: Initial address of receive buffer (choice).
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.IP \(bu 2
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\fBstatus\fP: Status object (status). This refers to the receive operation.
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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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The send\-receive operations combine in one call the sending of a message
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to one destination and the receiving of another message, from another
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process. The two (source and destination) are possibly the same. A
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send\-receive operation is useful for executing a shift operation across
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a chain of processes. If blocking sends and receives are used for such a
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shift, then one needs to order the sends and receives correctly (for
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example, even processes send, then receive; odd processes receive first,
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then send) in order to prevent cyclic dependencies that may lead to
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deadlock. When a send\-receive operation is used, the communication
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subsystem takes care of these issues. The send\-receive operation can be
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used in conjunction with the functions described in the “Process
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Topologies” chapter in the \fI\%MPI Standard\fP in order to perform shifts on
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various logical topologies. Also, a send\-receive operation is useful for
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implementing remote procedure calls.
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.sp
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A message sent by a send\-receive operation can be received by a regular
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receive operation or probed by a probe operation; a send\-receive
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operation can receive a message sent by a regular send operation.
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.sp
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\fI\%MPI_Sendrecv\fP executes a blocking send and receive operation. Both send
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and receive use the same communicator, but possibly different tags. The
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send buffer and receive buffers must be disjoint, and may have different
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lengths and datatypes.
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.sp
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If your application does not need to examine the \fIstatus\fP field, you can
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save resources by using the predefined constant \fBMPI_STATUS_IGNORE\fP as a
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special value for the \fIstatus\fP argument.
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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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Note that per the “Return Status” section in the “Point\-to\-Point
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Communication” chapter in the \fI\%MPI Standard\fP, MPI errors on messages received
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by \fI\%MPI_Sendrecv\fP do not set the \fBstatus.MPI_ERROR\fP field in
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the returned \fIstatus\fP\&. The error code is always passed to the
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back\-end error handler and may be passed back to the caller through
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the return value of \fI\%MPI_Sendrecv\fP if the back\-end error handler
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returns it. The pre\-defined MPI error handler \fBMPI_ERRORS_RETURN\fP
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exhibits this behavior, for example.
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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_Sendrecv_replace\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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