NAME

MPI_Test - A non-blocking test to see if a request is complete

SYNOPSIS

#include <mpi.h> 
int MPI_Test(MPI_Request *rq , int *flag , MPI_Status *status ); 
#include <pmpi.h> 
int PMPI_Test(MPI_Request *rq , int *flag , MPI_Status *status ); 
#include <mpi.h> 
bool MPI::Request::Test(MPI::Status &status ); 
bool MPI::Request::Test(void); 
INCLUDE 'mpif.h' 
MPI_TEST(rq , flag , status , ierr ) 
INTEGER  rq ,  flag ,  status (MPI_STATUS_SIZE),  ierr 

INPUT PARAMETER

rq - request (handle)

OUTPUT PARAMETERS

flag - is the request complete (boolean)

status - status information about the request (structure)

DESCRIPTION

The MPI_Test() function is used to test in a non-blocking manner whether or not a request has completed. If it has, then flag is set to one. Otherwise it will be set to zero. Information about the request will be stored in status .

On completion, the original tag and source of a recieved message are stored in the MPI_TAG and MPI_SOURCE fields of the status respectively. If the received message has been truncated then MPI_ERROR will be set to be MPI_ERR_TRUNCATE. One additional field holds the total size of the message in bytes. If either a send or receive is successfully cancelled, then MPI_ERROR will contain MPI_ERR_CANCEL. Otherwise, it will be set to MPI_ERR_SUCCESS. If status is MPI_STATUS_IGNORE then this information will not be stored.

If the request is invalid, then the status is filled with MPI_ANY_TAG MPI_PROC_NULL MPI_SUCCESS and zero size in bytes. PMPI_Test() is the profiling version of this function.

The resulting value in the MPI_ERROR field of status will be returned as the result of this function. If it is not MPI_SUCCESS then an error handler will be called.

The C++ version of this function passes the flag output as the return value.

ERRORS

All MPI routines except for MPI_Wtime and MPI_Wtick return an error code. The the current MPI error handler is invoked if the return value is not MPI_SUCCESS. The default error handler aborts, but this may be changed with by using the MPI_Errhandler_set() function. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned instead. Note that MPI does not guarentee that an MPI program can continue past an error. In this implementation, all errors except MPI_ERR_INTERN or MPI_ERR_OTHER should always be recoverable.

In C, the error code is passed as the return value. In FORTRAN, all functions have an parameter ierr which returns the error code. MPI C++ functions do not directly return an error code. However, C++ users may want to use the MPI::ERRORS_THROW_EXCEPTIONS handler. This will throw an MPI::Exception with the corresponding error code. To prevent exceptions from being raised from within C and Fortran code, they will see all error return values as MPI_ERR_PENDING when this handler is chosen. In this implementation, call MPI::throw_exception() to throw the correct exception if this occurs.

MPI_SUCCESS - No error;

MPI_ERR_PENDING - Pending exception;

MPI_ERR_ARG - Invalid flag pointer;

MPI_ERR_TRUNCATE - Receive buffer was too small;

MPI_ERR_CANCEL - Message was canceled.

SEE ALSO

MPI_Probe (3) MPI_Isend (3) MPI_Irecv (3) MPI_Testall (3) MPI_Testany (3) MPI_Testsome (3) MPI_Wait (3)

• Lockless
• MPI Documentation
• MPI_Test