MPI_Test(3) Open MPI MPI_Test(3)
NAME
MPI_Test - Tests for the completion of a specific send or receive.
SYNTAX
C Syntax
#include <mpi.h>
int MPI_Test(MPI_Request *request, int *flag, MPI_Status *status)
Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TEST(REQUEST, FLAG, STATUS, IERROR)
LOGICAL FLAG
INTEGER REQUEST, STATUS(MPI_STATUS_SIZE), IERROR
Fortran 2008 Syntax
USE mpi_f08
MPI_Test(request, flag, status, ierror)
TYPE(MPI_Request), INTENT(INOUT) :: request
LOGICAL, INTENT(OUT) :: flag
TYPE(MPI_Status) :: status
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
C++ Syntax
#include <mpi.h>
bool Request::Test(Status& status)
bool Request::Test()
INPUT PARAMETER
request Communication request (handle).
OUTPUT PARAMETERS
flag True if operation completed (logical).
status Status object (status).
IERROR Fortran only: Error status (integer).
DESCRIPTION
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 con-
tain information on the completed operation; if the communication ob-
ject was created by a nonblocking send or receive, then it is deallo-
cated and the request handle is set to MPI_REQUEST_NULL. The call re-
turns flag = false, otherwise. In this case, the value of the status
object is undefined. MPI_Test is a local operation.
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 Stan-
dard, "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").
If your application does not need to examine the status field, you can
save resources by using the predefined constant MPI_STATUS_IGNORE as a
special value for the status argument.
One is allowed to call MPI_Test with a null or inactive request argu-
ment. In such a case the operation returns with flag = true and empty
status.
The functions MPI_Wait and MPI_Test can be used to complete both sends
and receives.
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.
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++ func-
tions 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.
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, MPI_File_set_errhandler, or MPI_Win_set_er-
rhandler (depending on the type of MPI handle that generated the re-
quest); 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.
Note that per MPI-1 section 3.2.5, MPI exceptions on requests passed to
MPI_TEST do not set the status.MPI_ERROR field in the returned status.
The error code is passed to the back-end error handler and may be
passed back to the caller through the return value of MPI_TEST if the
back-end error handler returns it. The pre-defined MPI error handler
MPI_ERRORS_RETURN exhibits this behavior, for example.
SEE ALSO
MPI_Comm_set_errhandler
MPI_File_set_errhandler
MPI_Testall
MPI_Testany
MPI_Testsome
MPI_Wait
MPI_Waitall
MPI_Waitany
MPI_Waitsome
MPI_Win_set_errhandler
4.1.2 Nov 24, 2021 MPI_Test(3)
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