218 lines
7.1 KiB
Groff
218 lines
7.1 KiB
Groff
.\" Man page generated from reStructuredText.
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.TH "MPI_IMRECV" "3" "Feb 14, 2025" "" "Open MPI"
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.sp
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\fI\%MPI_Imrecv\fP — Non\-blocking receive for a matched 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_Imrecv(void *buf, int count, MPI_Datatype type,
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MPI_Message *message, 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_IMRECV(BUF, COUNT, DATATYPE, MESSAGE, REQUEST, IERROR)
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<type> BUF(*)
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INTEGER COUNT, DATATYPE, MESSAGE, 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_Imrecv(buf, count, datatype, message, request, ierror)
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TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
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INTEGER, INTENT(IN) :: count
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TYPE(MPI_Datatype), INTENT(IN) :: datatype
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TYPE(MPI_Message), INTENT(INOUT) :: message
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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 PARAMETERS
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.INDENT 0.0
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.IP \(bu 2
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\fBcount\fP: Number of elements to receive (nonnegative integer).
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.IP \(bu 2
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\fBdatatype\fP: Datatype of each send buffer element (handle).
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.IP \(bu 2
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\fBmessage\fP: Message (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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\fBbuf\fP: Initial address of receive buffer (choice).
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.IP \(bu 2
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\fBrequest\fP: Request (handle).
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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 functions \fI\%MPI_Mrecv\fP and \fI\%MPI_Imrecv\fP receive messages that have been
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previously matched by a matching probe.
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.sp
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The \fIrequest\fP returned from \fI\%MPI_Imrecv\fP can be used with any of the
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\fI\%MPI_Test\fP and \fI\%MPI_Wait\fP variants, like any non\-blocking receive request.
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.sp
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If \fI\%MPI_Imrecv\fP is called with \fBMPI_MESSAGE_NULL\fP as the message argument, a
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call to one of the \fI\%MPI_Test\fP or \fI\%MPI_Wait\fP variants will return immediately
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with the \fIstatus\fP object set to \fIsource\fP = \fBMPI_PROC_NULL\fP, \fItag\fP =
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\fBMPI_ANY_TAG\fP, and \fIcount\fP = 0, as if a receive from \fBMPI_PROC_NULL\fP was
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issued.
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.sp
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If reception of a matched message is started with \fI\%MPI_Imrecv\fP, then it is
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possible to cancel the returned request with \fI\%MPI_Cancel\fP\&. If \fI\%MPI_Cancel\fP
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succeeds, the matched message must be found by a subsequent message
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probe (\fI\%MPI_Probe\fP, \fI\%MPI_Iprobe\fP, \fI\%MPI_Mprobe\fP, or \fI\%MPI_Improbe\fP), received by a
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subsequent receive operation or canceled by the sender.
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.sp
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Note, however, that is it possible for the cancellation of operations
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initiated with \fI\%MPI_Imrecv\fP to fail. An example of a failing case is when
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canceling the matched message receive would violate MPI message ordering
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rules (e.g., if another message matching the same message signature has
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matched — and possibly received — before this \fI\%MPI_Imrecv\fP is canceled).
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.sp
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If your application does not need to examine the \fIstatus\fP field, you
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can save resources by using the predefined constant
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\fBMPI_STATUS_IGNORE\fP as a 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_Imrecv\fP do not set the \fBstatus.MPI_ERROR\fP field in the
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returned \fIstatus\fP\&. The error code is always passed to the back\-end
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error handler and may be passed back to the caller through the return
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value of \fI\%MPI_Imrecv\fP if the back\-end error handler returns it.
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The pre\-defined MPI error handler \fBMPI_ERRORS_RETURN\fP exhibits this
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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_Mprobe\fP
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.IP \(bu 2
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\fI\%MPI_Improbe\fP
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.IP \(bu 2
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\fI\%MPI_Probe\fP
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.IP \(bu 2
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\fI\%MPI_Iprobe\fP
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.IP \(bu 2
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\fI\%MPI_Imrecv\fP
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.IP \(bu 2
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\fI\%MPI_Cancel\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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