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NAME

MPI_Errhandler_create - Creates an error handler from a user function

SYNOPSIS

#include <mpi.h> int MPI_Errhandler_create(MPI_Handler_function *func , MPI_Errhandler *errh );

#include <pmpi.h> int PMPI_Errhandler_create(MPI_Handler_function *func , MPI_Errhandler *errh );

#include <mpi.h> void MPI::Errhandler::Create(MPI::Errhandler_function *func );

INCLUDE 'mpif.h' MPI_ERRHADNLER_CREATE(func , errh , ierr ) EXTERNAL func INTEGER errh , ierr

INPUT PARAMETER

func - error handling function (function pointer)

OUTPUT PARAMETER

errh - the new error handler handle (handle).

DESCRIPTION

The MPI_Errhandler_create() function is used to create an error handler handle errh from a user function, func . The handle may then be used to change the behaviour on error of communicators.

The handle should eventually be freed by the MPI_Errhandler_free() function.

Three default handles already exist. MPI_ERRORS_ARE_FATAL is the default handler that aborts with an error message. MPI_ERRORS_RETURN is a handler that will cause a failing function to return an error code. MPI_ERRORS_THROW_EXCEPTIONS is a handler that will throw an exception when used with the C++ language binding. With other bindings, MPI_ERR_PENDING will be returned. To throw the correct exception, then call the implementation-specific function MPI::throw_exception() . Exceptions are not raised when using C or Fortran bindings because those languages might not be compiled with the needed unwinding information.

PMPI_Errhandler_create() is the profiling version of this function.

The form of MPI_Handler_function is

typedef void MPI_Handler_function(MPI_Comm comm , int *err , ...);

INPUT PARAMETERS

comm - communicator (handle)

err - error code (integer)

OUTPUT PARAMETERS

err - error code (integer)

HANDLER FUNCTIONS

The handler function should in some way "handle" the error condition. The communicator corresponding to the error is passed to this function in comm . The error code is passed in err . However, note that err is passed via pointer. This allows the handler function to alter the error code condition. The resulting value will be returned to the user code calling the failing MPI routine via its return value.

The variable argument list contains one extra parameter, the name of the failing function. Note that this may not be a top-level routine exposed by the MPI interface, and could be the name of a low-level undocumented routine. This extra parameter is encoded as a C string, and may be accessed by using the va_args macros:

void example_handle_func(MPI_Comm *comm, int *err, ...) { va_list ap; const char *func;

va_start(ap, err); func = va_arg(ap, const char *); va_end(ap);

printf("Failing function: %sn", func); }

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 handle pointer.

SEE ALSO

MPI_Errhandler_free (3) MPI_Errhandler_set (3) MPI_Errhandler_get (3) MPI_Error_string (3) MPI_Error_class (3)

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