NAME

       MPI_Comm_get_attr - Retrieves attribute value by key.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Comm_get_attr(MPI_Comm comm, int comm_keyval,
            void *attribute_val, int *flag)

Fortran Syntax (see FORTRAN 77 NOTES)

       INCLUDE 'mpif.h'
       MPI_COMM_GET_ATTR(COMM, COMM_KEYVAL, ATTRIBUTE_VAL, FLAG, IERROR)
            INTEGER   COMM, COMM_KEYVAL, IERROR
            INTEGER(KIND=MPI_ADDRESS_KIND) ATTRIBUTE_VAL
            LOGICAL FLAG

C++ Syntax

       #include <mpi.h>
       bool MPI::Comm::Get_attr(int comm_keyval, void* attribute_val)
            const

INPUT PARAMETERS

       comm      Communicator to which the attribute is attached (handle).

       comm_keyval
                 Key value (integer).

OUTPUT PARAMETER

       attribute_val
                 Attribute value, unless flag = false.

       flag      False if no attribute is associated with the key (logical).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_Comm_get_attr  retrieves  an attribute value by key. The call is erroneous if there is
       no key with value keyval. On the other hand, the call is correct if the key value  exists,
       but  no  attribute is attached on comm for that key; in that case, the call returns flag =
       false. In particular, MPI_KEYVAL_INVALID is an erroneous key value.

       This function replaces MPI_Attr_get, the use of which is  deprecated.  The  C  binding  is
       identical. The Fortran binding differs in that attribute_val is an address-sized integer.

FORTRAN 77 NOTES

       The  MPI  standard  prescribes portable Fortran syntax for the ATTRIBUTE_VAL argument only
       for Fortran 90. Sun FORTRAN 77 users may use the non-portable syntax

            INTEGER*MPI_ADDRESS_KIND ATTRIBUTE_VAL

       where MPI_ADDRESS_KIND is a constant defined  in  mpif.h  and  gives  the  length  of  the
       declared integer in bytes.

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.