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
);

Parameters

type_copy_attr_fn

[in] copy callback function for type_keyval (function)

type_delete_attr_fn

[in] delete callback function for type_keyval (function)

type_keyval

[out] key value for future access (integer)

extra_state

[in] extra state for callback functions

Remarks

The argument type_copy_attr_fn may be specified as MPI_TYPE_NULL_COPY_FN or MPI_TYPE_DUP_FN from either 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 either C, C++, or Fortran. MPI_TYPE_NULL_DELETE_FN is a function that does nothing, other than 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);
 

Default copy and delete functions are available. These are

MPI_TYPE_NULL_COPY_FN

empty copy function

MPI_TYPE_NULL_DELETE_FN

empty delete function

MPI_TYPE_DUP_FN

simple dup function

Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

Notes for Fortran

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.

Errors

All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

MPI_SUCCESS

No error; MPI routine completed successfully.

MPI_ERR_OTHER

Other error; use MPI_Error_string to get more information about this error code.

Example Code

The following sample code illustrates MPI_Type_create_keyval.