1 | .\"Copyright 2006-2008 Sun Microsystems, Inc. |
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2 | .\" Copyright (c) 1996 Thinking Machines Corporation |
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3 | .\"Copyright 2007-2008 Cisco Systems, Inc. All rights reserved. |
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4 | .TH MPI_Test 3 "Dec 08, 2009" "1.4" "Open MPI" |
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5 | .SH NAME |
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6 | \fBMPI_Test\fP \- Tests for the completion of a specific send or receive. |
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7 | |
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8 | .SH SYNTAX |
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9 | .ft R |
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10 | .SH C Syntax |
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11 | .nf |
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12 | #include <mpi.h> |
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13 | int MPI_Test(MPI_Request *\fIrequest\fP, int\fI *flag\fP, MPI_Status\fI *status\fP) |
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14 | |
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15 | .SH Fortran Syntax |
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16 | .nf |
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17 | INCLUDE 'mpif.h' |
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18 | MPI_TEST(\fIREQUEST, FLAG, STATUS, IERROR\fP) |
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19 | LOGICAL \fIFLAG\fP |
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20 | INTEGER \fIREQUEST, STATUS(MPI_STATUS_SIZE), IERROR\fP |
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21 | |
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22 | .SH C++ Syntax |
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23 | .nf |
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24 | #include <mpi.h> |
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25 | bool Request::Test(Status& \fIstatus\fP) |
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26 | |
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27 | bool Request::Test() |
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28 | |
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29 | .SH INPUT PARAMETER |
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30 | .ft R |
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31 | .TP 1i |
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32 | request |
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33 | Communication request (handle). |
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34 | |
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35 | .SH OUTPUT PARAMETERS |
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36 | .ft R |
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37 | .TP 1i |
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38 | flag |
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39 | True if operation completed (logical). |
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40 | .TP 1i |
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41 | status |
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42 | Status object (status). |
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43 | .ft R |
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44 | .TP 1i |
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45 | IERROR |
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46 | Fortran only: Error status (integer). |
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47 | |
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48 | .SH DESCRIPTION |
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49 | .ft R |
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50 | A call to MPI_Test returns flag = true if the operation identified by request is complete. In such a case, the status object is set to contain information on the completed operation; if the communication object was created by a nonblocking send or receive, then it is deallocated and the request handle is set to MPI_REQUEST_NULL. The call returns flag = false, otherwise. In this case, the value of the status object is undefined. MPI_Test is a local operation. |
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51 | .sp |
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52 | The return status object for a receive operation carries information that can be accessed as described in Section 3.2.5 of the MPI-1 Standard, "Return Status." The status object for a send operation carries information that can be accessed by a call to MPI_Test_cancelled (see Section 3.8 of the MPI-1 Standard, "Probe and Cancel"). |
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53 | .sp |
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54 | 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. |
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55 | .sp |
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56 | One is allowed to call MPI_Test with a null or inactive \fIrequest\fP argument. In such a case the operation returns with \fIflag\fP = true and empty \fIstatus\fP. |
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57 | .sp |
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58 | The functions MPI_Wait and MPI_Test can be used to complete both sends and |
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59 | receives. |
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60 | |
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61 | .SH NOTES |
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62 | The use of the nonblocking MPI_Test call allows the user to schedule alternative activities within a single thread of execution. An event-driven thread scheduler can be emulated with periodic calls to MPI_Test. |
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63 | |
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64 | .SH ERRORS |
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65 | 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. |
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66 | .sp |
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67 | Before the error value is returned, the current MPI error handler is |
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68 | called. By default, this error handler aborts the MPI job, except for |
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69 | I/O function errors. The error handler may be changed with |
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70 | MPI_Comm_set_errhandler, MPI_File_set_errhandler, or |
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71 | MPI_Win_set_errhandler (depending on the type of MPI handle that |
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72 | generated the request); the predefined error handler MPI_ERRORS_RETURN |
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73 | may be used to cause error values to be returned. Note that MPI does |
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74 | not guarantee that an MPI program can continue past an error. |
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75 | .sp |
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76 | Note that per MPI-1 section 3.2.5, MPI exceptions on requests passed |
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77 | to MPI_TEST do not set the status.MPI_ERROR field in the returned |
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78 | status. The error code is passed to the back-end error handler |
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79 | and may be passed back to the caller through the return value of |
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80 | MPI_TEST if the back-end error handler returns it. The |
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81 | pre-defined MPI error handler MPI_ERRORS_RETURN exhibits this |
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82 | behavior, for example. |
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83 | |
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84 | .SH SEE ALSO |
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85 | .ft R |
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86 | .sp |
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87 | MPI_Comm_set_errhandler |
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88 | .br |
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89 | MPI_File_set_errhandler |
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90 | .br |
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91 | MPI_Testall |
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92 | .br |
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93 | MPI_Testany |
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94 | .br |
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95 | MPI_Testsome |
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96 | .br |
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97 | MPI_Wait |
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98 | .br |
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99 | MPI_Waitall |
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100 | .br |
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101 | MPI_Waitany |
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102 | .br |
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103 | MPI_Waitsome |
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104 | .br |
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105 | MPI_Win_set_errhandler |
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106 | .br |
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107 | |
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