debian man page for mpi_comm_get_attr

MPI_Comm_get_attr(3)							MPI						      MPI_Comm_get_attr(3)

NAME
       MPI_Comm_get_attr -  Retrieves attribute value by key

SYNOPSIS
       int MPI_Comm_get_attr(MPI_Comm comm, int comm_keyval, void *attribute_val,
			    int *flag)

INPUT PARAMETERS
       comm   - communicator to which attribute is attached (handle)
       keyval - key value (integer)

OUTPUT PARAMETERS
       attr_value
	      - attribute value, unless flag = false
       flag   - true if an attribute value was extracted;  false if no attribute is associated with the key

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

NOTES FOR C
       Even though the attr_value arguement is declared as void * , it is really the address of a void pointer.  See the rationale in the standard
       for more details.

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 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.

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_COMM
	      - Invalid communicator.  A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank ).
       MPI_ERR_KEYVAL
	      - Invalid keyval

LOCATION
       comm_get_attr.c

								     2/4/2011						      MPI_Comm_get_attr(3)