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NAME

       MPI_Attr_get -  Retrieves attribute value by key

SYNOPSIS

       int MPI_Attr_get(MPI_Comm comm, int keyval, void *attribute_val, int *flag)

INPUT PARAMETERS

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

OUTPUT PARAMETERS

       attribute_val
              - 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_ATTR_PUT .  The notes for C and Fortran below explain why.

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.

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.

DEPRECATED FUNCTION

       The MPI-2 standard deprecated a number of routines because MPI-2 provides better versions.
       This  routine  is  one of those that was deprecated.  The routine may continue to be used,
       but new code should use the replacement routine.  The  replacement  for  this  routine  is
       MPI_Comm_get_attr .

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 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

SEE ALSO

       MPI_Attr_put, MPI_Keyval_create, MPI_Attr_delete, MPI_Comm_get_attr

                                            11/21/2018                            MPI_Attr_get(3)