108 строки
3.8 KiB
Groff
108 строки
3.8 KiB
Groff
.\"Copyright 2006, Sun Microsystems, Inc.
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.\" Copyright (c) 1996 Thinking Machines Corporation
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.\"Copyright 2007, Cisco Systems, Inc. All rights reserved.
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.TH MPI_Test 3OpenMPI "September 2006" "Open MPI 1.2" " "
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.SH NAME
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\fBMPI_Test\fP \- Tests for the completion of a specific send or receive.
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.SH SYNTAX
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.ft R
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.SH C Syntax
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.nf
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#include <mpi.h>
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int MPI_Test(MPI_Request *\fIrequest\fP, int\fI *flag\fP, MPI_Status\fI *status\fP)
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.SH Fortran Syntax
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.nf
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INCLUDE 'mpif.h'
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MPI_TEST(\fIREQUEST, FLAG, STATUS, IERROR\fP)
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LOGICAL \fIFLAG\fP
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INTEGER \fIREQUEST, STATUS(MPI_STATUS_SIZE), IERROR\fP
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.SH C++ Syntax
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.nf
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#include <mpi.h>
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bool Request::Test(Status& \fIstatus\fP)
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bool Request::Test()
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.SH INPUT PARAMETER
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.ft R
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.TP 1i
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request
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Communication request (handle).
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.SH OUTPUT PARAMETERS
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.ft R
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.TP 1i
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flag
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True if operation completed (logical).
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.TP 1i
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status
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Status object (status).
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.ft R
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.TP 1i
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IERROR
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Fortran only: Error status (integer).
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.SH DESCRIPTION
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.ft R
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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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.sp
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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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.sp
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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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.sp
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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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.sp
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The functions MPI_Wait and MPI_Test can be used to complete both sends and
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receives.
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.SH NOTES
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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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.SH ERRORS
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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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.sp
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Before the error value is returned, the current MPI error handler is
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called. By default, this error handler aborts the MPI job, except for
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I/O function errors. The error handler may be changed with
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MPI_Comm_set_errhandler, MPI_File_set_errhandler, or
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MPI_Win_set_errhandler (depending on the type of MPI handle that
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generated the request); the predefined error handler MPI_ERRORS_RETURN
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may be used to cause error values to be returned. Note that MPI does
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not guarantee that an MPI program can continue past an error.
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.sp
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Note that per MPI-1 section 3.2.5, MPI exceptions on requests passed
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to MPI_TEST do not set the status.MPI_ERROR field in the returned
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status. The error code is passed to the back-end error handler
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and may be passed back to the caller through the return value of
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MPI_TEST if the back-end error handler returns it. The
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pre-defined MPI error handler MPI_ERRORS_RETURN exhibits this
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behavior, for example.
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.SH SEE ALSO
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.ft R
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.sp
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MPI_Comm_set_errhandler
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.br
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MPI_File_set_errhandler
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.br
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MPI_Testall
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.br
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MPI_Testany
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.br
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MPI_Testsome
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.br
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MPI_Wait
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.br
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MPI_Waitall
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.br
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MPI_Waitany
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.br
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MPI_Waitsome
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.br
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MPI_Win_set_errhandler
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.br
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