.\"Copyright 2006, Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.
.\" Copyright (c) 1996 Thinking Machines Corporation
.TH MPI_Test 3OpenMPI "September 2006" "Open MPI 1.2" " "
.SH NAME
\fBMPI_Test\fP \- Tests for the completion of a specific send or receive.

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Test(MPI_Request *\fIrequest\fP, int\fI *flag\fP, MPI_Status\fI *status\fP)

.SH Fortran Syntax
.nf
INCLUDE 'mpif.h'
MPI_TEST(\fIREQUEST, FLAG, STATUS, IERROR\fP)
	LOGICAL	\fIFLAG\fP
	INTEGER	\fIREQUEST, STATUS(MPI_STATUS_SIZE), IERROR\fP 

.SH C++ Syntax
.nf
#include <mpi.h>
bool Request::Test(Status& \fIstatus\fP)

bool Request::Test()

.SH INPUT PARAMETER
.ft R
.TP 1i
request
Communication request (handle).

.SH OUTPUT PARAMETERS
.ft R
.TP 1i
flag
True if operation completed (logical).
.TP 1i
status
Status object (status).
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer). 

.SH DESCRIPTION
.ft R
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.  
.sp
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").
.sp
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. 
.sp
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.
.sp
The functions MPI_Wait and MPI_Test can be used to complete both sends and
receives.

.SH NOTES
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. 

.SH ERRORS
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.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.  

.SH SEE ALSO
.ft R
.sp
MPI_Wait

' @(#)MPI_Test.3 1.20 06/03/09