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.TH "MPI_ISENDRECV" "3" "Apr 08, 2024" "" "Open MPI"
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.sp
\fI\%MPI_Isendrecv\fP — Sends and receives a message.
.SH SYNTAX
.SS C Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
#include <mpi.h>

int MPI_Isendrecv(const void *sendbuf, int sendcount, MPI_Datatype sendtype,
    int dest, int sendtag, void *recvbuf, int recvcount,
    MPI_Datatype recvtype, int source, int recvtag,
    MPI_Comm comm, MPI_Request *request)
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
USE MPI
! or the older form: INCLUDE \(aqmpif.h\(aq
MPI_ISENDRECV(SENDBUF, SENDCOUNT, SENDTYPE, DEST, SENDTAG,
        RECVBUF, RECVCOUNT, RECVTYPE, SOURCE, RECVTAG, COMM,
        REQUEST, IERROR)
    <type>    SENDBUF(*), RECVBUF(*)
    INTEGER    SENDCOUNT, SENDTYPE, DEST, SENDTAG
    INTEGER    RECVCOUNT, RECVTYPE, SOURCE, RECVTAG, COMM
    INTEGER    REQUEST, IERROR
.ft P
.fi
.UNINDENT
.UNINDENT
.SS Fortran 2008 Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
USE mpi_f08
MPI_Isendrecv(sendbuf, sendcount, sendtype, dest, sendtag, recvbuf,
        recvcount, recvtype, source, recvtag, comm, request, ierror)
    TYPE(*), DIMENSION(..), INTENT(IN) :: sendbuf
    TYPE(*), DIMENSION(..) :: recvbuf
    INTEGER, INTENT(IN) :: sendcount, dest, sendtag, recvcount, source,
    recvtag
    TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
    TYPE(MPI_Comm), INTENT(IN) :: comm
    TYPE(MPI_Request) :: request
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror
.ft P
.fi
.UNINDENT
.UNINDENT
.SH INPUT PARAMETERS
.INDENT 0.0
.IP \(bu 2
\fBsendbuf\fP: Initial address of send buffer (choice).
.IP \(bu 2
\fBsendcount\fP: Number of elements to send (integer).
.IP \(bu 2
\fBsendtype\fP: Type of elements in send buffer (handle).
.IP \(bu 2
\fBdest\fP: Rank of destination (integer).
.IP \(bu 2
\fBsendtag\fP: Send tag (integer).
.IP \(bu 2
\fBrecvcount\fP: Maximum number of elements to receive (integer).
.IP \(bu 2
\fBrecvtype\fP: Type of elements in receive buffer (handle).
.IP \(bu 2
\fBsource\fP: Rank of source (integer).
.IP \(bu 2
\fBrecvtag\fP: Receive tag (integer).
.IP \(bu 2
\fBcomm\fP: Communicator (handle).
.UNINDENT
.SH OUTPUT PARAMETERS
.INDENT 0.0
.IP \(bu 2
\fBrecvbuf\fP: Initial address of receive buffer (choice).
.IP \(bu 2
\fBrequest\fP: Communication request (handle).
.IP \(bu 2
\fBierror\fP: Fortran only: Error status (integer).
.UNINDENT
.SH DESCRIPTION
.sp
The non\-blocking send\-receive operations combine in one call the sending
of a message to one destination and the receiving of another message,
from another process. The two (source and destination) are possibly the
same. This operation is useful for executing a shift operation across a
chain of processes. The send\-receive operation can be used in
conjunction with the functions described in the “Process Topologies”
chapter of the MPI Standard in order to perform shifts on various
logical topologies.
.sp
A message sent by a send\-receive operation can be received by a regular
receive operation or probed by a probe operation; a send\-receive
operation can receive a message sent by a regular send operation.
.sp
\fI\%MPI_Isendrecv\fP executes a non\-blocking send and receive operation. Both
send and receive use the same communicator, but possibly different tags.
The send buffer and receive buffers must be disjoint, and may have
different lengths and datatypes.
.sp
A non\-blocking send\-receive request can be determined to be completed by
calling the \fI\%MPI_Wait\fP, \fI\%MPI_Waitany\fP, \fI\%MPI_Test\fP, or \fI\%MPI_Testany\fP with the
request returned by this function.
.SH ERRORS
.sp
Almost all MPI routines return an error value; C routines as the return result
of the function and Fortran routines in the last argument.
.sp
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
\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
Model exclusively) the error raises the initial error handler. The initial
error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
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.
.sp
Open MPI includes three predefined error handlers that can be used:
.INDENT 0.0
.IP \(bu 2
\fBMPI_ERRORS_ARE_FATAL\fP
Causes the program to abort all connected MPI processes.
.IP \(bu 2
\fBMPI_ERRORS_ABORT\fP
An error handler that can be invoked on a communicator,
window, file, or session. When called on a communicator, it
acts as if \fI\%MPI_Abort\fP was called on that communicator. If
called on a window or file, acts as if \fI\%MPI_Abort\fP 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.
.IP \(bu 2
\fBMPI_ERRORS_RETURN\fP
Returns an error code to the application.
.UNINDENT
.sp
MPI applications can also implement their own error handlers by calling:
.INDENT 0.0
.IP \(bu 2
\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
.IP \(bu 2
\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
.UNINDENT
.sp
Note that MPI does not guarantee that an MPI program can continue past
an error.
.sp
See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
.sp
See the Error Handling section of the MPI\-3.1 standard for
more information.
.sp
\fBSEE ALSO:\fP
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.INDENT 3.5
.INDENT 0.0
.IP \(bu 2
\fI\%MPI_Isendrecv_replace\fP
.IP \(bu 2
\fI\%MPI_Sendrecv\fP
.IP \(bu 2
\fI\%MPI_Sendrecv_replace\fP
.UNINDENT
.UNINDENT
.UNINDENT
.SH COPYRIGHT
2003-2024, The Open MPI Community
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