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MPI_Test - Tests for the completion of a specific send or receive.
#include <mpi.h>
int MPI_Test(MPI_Request *request, int *flag, MPI_Status *status)
INCLUDE ’mpif.h’
MPI_TEST(REQUEST, FLAG, STATUS, IERROR)
LOGICAL FLAG
INTEGER REQUEST, STATUS(MPI_STATUS_SIZE), IERROR
#include <mpi.h>
bool Request::Test(Status& status)
bool Request::Test()
- request
- Communication request (handle).
- flag
- True if operation completed (logical).
- status
- Status object (status).
- IERROR
- Fortran only: Error status (integer).
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.
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").
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 argument. 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.
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.
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.
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_errhandler (depending on the type of MPI handle that generated
the request); 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.
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
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