1 | .\"Copyright 2007-2008 Sun Microsystems, Inc. |
---|
2 | .\" Copyright (c) 1996 Thinking Machines Corporation |
---|
3 | .TH MPI_Wait 3 "Dec 08, 2009" "1.4" "Open MPI" |
---|
4 | .SH NAME |
---|
5 | \fBMPI_Wait\fP \- Waits for an MPI send or receive to complete. |
---|
6 | |
---|
7 | .SH SYNTAX |
---|
8 | .ft R |
---|
9 | .SH C Syntax |
---|
10 | .nf |
---|
11 | #include <mpi.h> |
---|
12 | int MPI_Wait(MPI_Request *\fIrequest\fP, MPI_Status\fI *status\fP) |
---|
13 | |
---|
14 | .SH Fortran Syntax |
---|
15 | .nf |
---|
16 | INCLUDE 'mpif.h' |
---|
17 | MPI_WAIT(\fIREQUEST, STATUS, IERROR\fP) |
---|
18 | INTEGER \fIREQUEST, STATUS(MPI_STATUS_SIZE), IERROR\fP |
---|
19 | |
---|
20 | .SH C++ Syntax |
---|
21 | .nf |
---|
22 | #include <mpi.h> |
---|
23 | void Request::Wait(Status& \fIstatus\fP) |
---|
24 | |
---|
25 | void Request::Wait() |
---|
26 | |
---|
27 | .SH INPUT PARAMETER |
---|
28 | .ft R |
---|
29 | .TP 1i |
---|
30 | request |
---|
31 | Request (handle). |
---|
32 | .sp |
---|
33 | .SH OUTPUT PARAMETERS |
---|
34 | .ft R |
---|
35 | .TP 1i |
---|
36 | status |
---|
37 | Status object (status). |
---|
38 | .ft R |
---|
39 | .TP 1i |
---|
40 | IERROR |
---|
41 | Fortran only: Error status (integer). |
---|
42 | |
---|
43 | .SH DESCRIPTION |
---|
44 | .ft R |
---|
45 | A call to MPI_Wait returns when the operation identified by request is complete. If the communication object associated with this request was created by a nonblocking send or receive call, then the object is deallocated by the call to MPI_Wait and the request handle is set to MPI_REQUEST_NULL. |
---|
46 | .sp |
---|
47 | The call returns, in status, information on the completed operation. The content of the status object for a receive operation can be accessed as described in Section 3.2.5 of the MPI-1 Standard, "Return Status." The status object for a send operation may be queried by a call to MPI_Test_cancelled (see Section 3.8 of the MPI-1 Standard, "Probe and Cancel"). |
---|
48 | .sp |
---|
49 | If your application does not need to examine the \fIstatus\fP field, you can save resources by using the predefined constant MPI_STATUS_IGNORE as a special value for the \fIstatus\fP argument. |
---|
50 | .sp |
---|
51 | One is allowed to call MPI_Wait with a null or inactive request argument. In this case the operation returns immediately with empty status. |
---|
52 | |
---|
53 | .SH NOTES |
---|
54 | Successful return of MPI_Wait after an MPI_Ibsend implies that the user send buffer can be reused i.e., data has been sent out or copied into a buffer attached with MPI_Buffer_attach. Note that, at this point, we can no longer cancel the send (for more information, see Section 3.8 of the MPI-1 Standard, "Probe and Cancel"). If a matching receive is never posted, then the buffer cannot be freed. This runs somewhat counter to the stated goal of MPI_Cancel (always being able to free program space that was committed to the communication subsystem). |
---|
55 | .sp |
---|
56 | Example: Simple usage of nonblocking operations and MPI_Wait. |
---|
57 | .sp |
---|
58 | .nf |
---|
59 | CALL MPI_COMM_RANK(comm, rank, ierr) |
---|
60 | IF(rank.EQ.0) THEN |
---|
61 | CALL MPI_ISEND(a(1), 10, MPI_REAL, 1, tag, comm, request, ierr) |
---|
62 | **** do some computation **** |
---|
63 | CALL MPI_WAIT(request, status, ierr) |
---|
64 | ELSE |
---|
65 | CALL MPI_IRECV(a(1), 15, MPI_REAL, 0, tag, comm, request, ierr) |
---|
66 | **** do some computation **** |
---|
67 | CALL MPI_WAIT(request, status, ierr) |
---|
68 | END IF |
---|
69 | |
---|
70 | .SH ERRORS |
---|
71 | Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object. |
---|
72 | .sp |
---|
73 | Before the error value is returned, the current MPI error handler is |
---|
74 | called. By default, this error handler aborts the MPI job, except for |
---|
75 | I/O function errors. The error handler may be changed with |
---|
76 | MPI_Comm_set_errhandler, MPI_File_set_errhandler, or |
---|
77 | MPI_Win_set_errhandler (depending on the type of MPI handle that |
---|
78 | generated the request); the predefined error handler MPI_ERRORS_RETURN |
---|
79 | may be used to cause error values to be returned. Note that MPI does |
---|
80 | not guarantee that an MPI program can continue past an error. |
---|
81 | .sp |
---|
82 | Note that per MPI-1 section 3.2.5, MPI exceptions on requests passed |
---|
83 | to MPI_WAIT do not set the status.MPI_ERROR field in the returned |
---|
84 | status. The error code is passed to the back-end error handler |
---|
85 | and may be passed back to the caller through the return value of |
---|
86 | MPI_WAIT if the back-end error handler returns it. The |
---|
87 | pre-defined MPI error handler MPI_ERRORS_RETURN exhibits this |
---|
88 | behavior, for example. |
---|
89 | |
---|
90 | .SH SEE ALSO |
---|
91 | .ft R |
---|
92 | .sp |
---|
93 | MPI_Comm_set_errhandler |
---|
94 | .br |
---|
95 | MPI_File_set_errhandler |
---|
96 | .br |
---|
97 | MPI_Test |
---|
98 | .br |
---|
99 | MPI_Testall |
---|
100 | .br |
---|
101 | MPI_Testany |
---|
102 | .br |
---|
103 | MPI_Testsome |
---|
104 | .br |
---|
105 | MPI_Waitall |
---|
106 | .br |
---|
107 | MPI_Waitany |
---|
108 | .br |
---|
109 | MPI_Waitsome |
---|
110 | .br |
---|
111 | MPI_Win_set_errhandler |
---|
112 | .br |
---|
113 | |
---|