MPI_Type_create_keyval(3) 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)

Fortran Syntax (see FORTRAN 77 NOTES)

INCLUDE 'mpif.h'
MPI_TYPE_CREATE_KEYVAL(TYPE_COPY_ATTR_FN, TYPE_DELETE_ATTR_FN, 
                TYPE_KEYVAL, EXTRA_STATE, IERROR)
        EXTERNAL TYPE_COPY_ATTR_FN, TYPE_DELETE_ATTR_FN
        INTEGER TYPE_KEYVAL, IERROR 
        INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE

C++ Syntax

#include <mpi.h>
static int MPI::Datatype::Create_keyval(MPI::Datatype::Copy_attr_function*
        type_copy_attr_fn, MPI::Datatype::Delete_attr_function*
        type_delete_attr_fn, 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.

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