MPI_Type_create_keyval(3)

NAME
MPI_Type_create_keyval - Generates a new attribute key for caching on data types.

SYNTAX

C Syntax
#include <mpi.h>
int MPI_Type_create_keyval(MPI_Type_copy_attr_function *type_copy_attr_fn,
	MPI_Type_delete_attr_function *type_delete_attr_fn,
	int *type_keyval, void *extra_state)

INPUT PARAMETERS

type_copy_attr_fn
    Copy callback function for type_keyval (function).

type_delete_attr_fn
    Delete callback function for type_keyval (function).

extra_state
    Extra state for callback functions.

OUTPUT PARAMETERS

type_keyval
    Key value for future access (integer).

IERROR
    Fortran only: Error status (integer).

DESCRIPTION
MPI_Type_create_keyval generates a new attribute key for caching on data types. This routine partially replaces MPI_Keyval_create.

The argument type_copy_attr_fn may be specified as MPI_TYPE_NULL_COPY_FN or MPI_TYPE_DUP_FN from C, C++, or Fortran. MPI_TYPE_NULL_COPY_FN is a function that does nothing other than returning flag = 0 and MPI_SUCCESS. MPI_TYPE_DUP_FN is a simple-minded copy function that sets flag = 1, returns the value of attribute_val_in in attribute_val_out, and returns MPI_SUCCESS.

The argument type_delete_attr_fn may be specified as MPI_TYPE_NULL_DELETE_FN from C, C++, or Fortran. MPI_TYPE_NULL_DELETE_FN is a function that does nothing beyond returning MPI_SUCCESS. The C callback functions are:

typedef int MPI_Type_copy_attr_function(MPI_Datatype oldtype,
            int type_keyval, void *extra_state, void *attribute_val_in,
            void *attribute_val_out, int *flag);
and
typedef int MPI_Type_delete_attr_function(MPI_Datatype type, int type_keyval,
             void *attribute_val, void *extra_state);

The Fortran callback functions are:

SUBROUTINE TYPE_COPY_ATTR_FN(OLDTYPE, TYPE_KEYVAL, EXTRA_STATE,
             ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT, FLAG, IERROR)
    INTEGER OLDTYPE, TYPE KEYVAL, IERROR
    INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE,
        ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT
    LOGICAL FLAG
and
SUBROUTINE TYPE_DELETE_ATTR_FN(TYPE, TYPE_KEYVAL, ATTRIBUTE_VAL, EXTRA_STATE,
             IERROR)
    INTEGER TYPE, TYPE_KEYVAL, IERROR
    INTEGER(KIND=MPI_ADDRESS_KIND) ATTRIBUTE VAL, EXTRA_STATE

The C++ callbacks are:

typedef int MPI::Datatype::Copy_attr_function(const MPI::Datatype& oldtype,
             int type_keyval, void* extra_state,
             const void* attribute_val_in, void* attribute_val_out,
             bool& flag);
and
typedef int MPI::Datatype::Delete_attr_function(MPI::Datatype& type,
             int type_keyval, void* attribute_val, void* extra_state);

FORTRAN 77 NOTES
The MPI standard prescribes portable Fortran syntax for the EXTRA_STATE argument only for Fortran 90. FORTRAN 77 users may use the non-portable syntax

     INTEGER*MPI_ADDRESS_KIND EXTRA_STATE

where MPI_ADDRESS_KIND is a constant defined in mpif.h and gives the length of the declared integer in bytes.

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.

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.

SEE ALSO

MPI_Type_free_keyval