MPI_Comm_create_keyval(3) MPI MPI_Comm_create_keyval(3) NAME MPI_Comm_create_keyval - Create a new attribute key SYNOPSIS int MPI_Comm_create_keyval(MPI_Comm_copy_attr_function *comm_copy_attr_fn, MPI_Comm_delete_attr_function *comm_delete_attr_fn, int *comm_keyval, void *extra_state) INPUT PARAMETERS comm_copy_attr_fn - copy callback function for comm_keyval (function) comm_delete_attr_fn - delete callback function for comm_keyval (function) extra_state - extra state for callback function (None) OUTPUT PARAMETERS comm_keyval - key value for future access (integer) NOTES Key values are global (available for any and all communicators). Default copy and delete functions are available. These are MPI_COMM_NULL_COPY_FN - empty copy function MPI_COMM_NULL_DELETE_FN - empty delete function MPI_COMM_DUP_FN - simple dup function There are subtle differences between C and Fortran that require that the copy_fn be written in the same language from which MPI_Comm_cre- ate_keyval is called. 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. RETURN VALUE FROM ATTRIBUTE CALLBACKS The MPI-2 versions of the attribute callbacks should return either MPI_SUC- CESS on success or a valid MPI error code or class on failure. The MPI standard is ambiguous on this point, but as MPI-2 provides the routines MPI_Add_error_class and MPI_Add_error_code that allow the user to define and use MPI error codes and classes. 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 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 inte- ger 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 state- ment. 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 ar- gument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error han- dler 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_OTHER - Other error; use MPI_Error_string to get more information about this error code. SEE ALSO MPI_Comm_free_keyval 4/10/2026 MPI_Comm_create_keyval(3)
NAME | SYNOPSIS | INPUT PARAMETERS | OUTPUT PARAMETERS | NOTES | RETURN VALUE FROM ATTRIBUTE CALLBACKS | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS | SEE ALSO
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