NAME

       MPI_Type_get_attr -  Retrieves attribute value by key

SYNOPSIS

       int MPI_Type_get_attr(MPI_Datatype datatype, int type_keyval,
       void *attribute_val, int *flag)

INPUT PARAMETERS

       datatype
              - datatype to which the attribute is attached (handle)
       type_keyval
              - key value (integer)

OUTPUT PARAMETERS

       attribute_val
              - attribute value, unless flag = false (None)
       flag   - false if no attribute is associated with the key (logical)

NOTES

       Attributes  must  be  extracted  from the same language as they were inserted in with MPI_ATTR_PUT .  The
       notes for C and Fortran below explain why.

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 C

       Even though the attribute_val argument is declared as void * , it is really the address of a void pointer
       (i.e., a void ** ).  Using a void * , however, is more in keeping with C idiom and allows the pointer  to
       be passed without additional casts.

NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the
       end of the argument list.  ierr is an integer and has the same meaning as the return value of the routine
       in C.  In Fortran, MPI routines are subroutines, and are invoked with the call statement.

       All  MPI  objects  (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.  The attribute_val in
       Fortran is a pointer to a Fortran integer, not a pointer to a void * .

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 guarantee 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_ARG
              -  Invalid  argument.   Some  argument  is invalid and is not identified by a specific error class
              (e.g., MPI_ERR_RANK ).
       MPI_ERR_KEYVAL
              - Invalid keyval
       MPI_ERR_TYPE
              - Invalid datatype argument.  Additionally, this error can occur if  an  uncommitted  MPI_Datatype
              (see MPI_Type_commit ) is used in a communication call.
       MPI_ERR_OTHER
              - Other error; use MPI_Error_string to get more information about this error code.

                                                    2/9/2024                                MPI_Type_get_attr(3)