NAME

       MPI_Keyval_create - Generates a new attribute key -- use of this routine is deprecated.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Keyval_create(MPI_Copy_function *copy_fn,
            MPI_Delete_function *delete_fn, int *keyval, void *extra_state)

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_KEYVAL_CREATE(COPY_FN, DELETE_FN, KEYVAL, EXTRA_STATE, IERROR)
            EXTERNAL  COPY_FN, DELETE_FN
            INTEGER   KEYVAL, EXTRA_STATE, IERROR

INPUT PARAMETERS

       copy_fn   Copy callback function for keyval.

       delete_fn Delete callback function for keyval.

       extra_state
                 Extra state for callback functions.

OUTPUT PARAMETERS

       keyval    Key value for future access (integer).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       Note that use of this routine is deprecated as of MPI-2. Please use MPI_Comm_create_keyval
       instead.

       This deprecated routine is not available in C++.

       Generates a new attribute key. Keys are locally unique in a  process  and  opaque  to  the
       user,  though they are explicitly stored in integers. Once allocated, the key value can be
       used to associate attributes and access them on any locally defined communicator.

       The copy_fn function is invoked when a communicator is duplicated by MPI_COMM_DUP. copy_fn
       should be of type MPI_Copy_function, which is defined as follows:

         typedef int MPI_Copy_function(MPI_Comm oldcomm, int keyval,
                                       void *extra_state, void *attribute_val_in,
                                       void *attribute_val_out, int *flag)

       A Fortran declaration for such a function is as follows:

         SUBROUTINE COPY_FUNCTION(OLDCOMM, KEYVAL, EXTRA_STATE, ATTRIBUTE_VAL_IN,
                     ATTRIBUTE_VAL_OUT, FLAG, IERR)
         INTEGER OLDCOMM, KEYVAL, EXTRA_STATE,
         ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT, IERR
         LOGICAL FLAG

       The  copy  callback  function is invoked for each key value in oldcomm in arbitrary order.
       Each call to the copy callback is made with a key value and its  corresponding  attribute.
       If  it  returns  flag  =  0, then the attribute is deleted in the duplicated communicator.
       Otherwise ( flag =  1),  the  new  attribute  value  is  set  to  the  value  returned  in
       attribute_val_out.  The  function  returns  MPI_SUCCESS  on  success  and an error code on
       failure (in which case MPI_Comm_dup will fail).

       copy_fn may be specified as MPI_NULL_COPY_FN or  MPI_DUP_FN  from  either  C  or  Fortran;
       MPI_NULL_COPY_FN  is  a  function  that  does  nothing  other  than  return  flag = 0, and
       MPI_SUCCESS. MPI_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.

NOTES

       Key values are global (available for any and all communicators).

       There  are  subtle  differences  between  C  and  Fortran that require that the copy_fn be
       written in the same language that MPI_Keyval_create is called from. This should not  be  a
       problem for most users; only programmers using both Fortran and C in the same program need
       to be sure that they follow this rule.

       Even though both formal arguments  attribute_val_in  and  attribute_val_out  are  of  type
       void*,  their  usage differs. The C copy function is passed by MPI in attribute_val_in the
       value of the attribute, and in attribute_val_out the address of the attribute,  so  as  to
       allow  the function to return the (new) attribute value. The use of type void* for both is
       to avoid messy type casts.

       A valid copy function is one that completely duplicates the information by making  a  full
       duplicate  copy  of  the  data structures implied by an attribute; another might just make
       another reference to that data structure, while using a reference-count  mechanism.  Other
       types of attributes might not copy at all (they might be specific to oldcomm only).

       Analogous  to  copy_fn  is a callback deletion function, defined as follows. The delete_fn
       function is invoked when a communicator is deleted by MPI_Comm_free or when a call is made
       explicitly  to  MPI_Attr_delete. delete_fn should be of type MPI_Delete_function, which is
       defined as follows:

         typedef int MPI_Delete_function(MPI_Comm comm, int keyval,
             void *attribute_val, void *extra_state);

       A Fortran declaration for such a function is as follows:

         SUBROUTINE DELETE_FUNCTION(COMM, KEYVAL,ATTRIBUTE_VAL, EXTRA_STATE, IERR)
             INTEGER COMM, KEYVAL, ATTRIBUTE_VAL, EXTRA_STATE, IERR

       This function is called by MPI_Comm_free, MPI_Attr_delete, and MPI_Attr_put to do whatever
       is needed to remove an attribute. The function returns MPI_SUCCESS on success and an error
       code on failure (in which case MPI_COMM_FREE will fail).

       delete_fn  may  be  specified  as   MPI_NULL_DELETE_FN   from   either   C   or   FORTRAN;
       MPI_NULL_DELETE_FN is a function that does nothing, other than returning MPI_SUCCESS.

       The   special  key  value  MPI_KEYVAL_INVALID  is  never  returned  by  MPI_Keyval_create.
       Therefore, it can be used for static initialization of key values.

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_Keyval_free
       MPI_Comm_create_keyval