MPI: added reduction function for scalar types

#endif

}

/**

 * \brief Applies the given reduction operation to the values among all ranks

 * in the given communicator.

 *

 * This is a collective operation which uses \ref Allreduce internally. It

 * provides nicer semantics than the wrapper function: the input value is passed

 * by value (heh) rather then by pointer, and the result is returned rather than

 * written to the output pointer.

 *

 * \param value Value of the current rank to be reduced.

 * \param op The reduction operation to be applied.

 * \param group The communicator comprising ranks that participate in the

 *              collective operation.

 * \return The reduced value (it is ensured that all ranks receive the same

 *         value).

 */

template< typename T >

T reduce( T value, const MPI_Op& op, MPI_Comm group = AllGroup() )

{

   // call the in-place variant of Allreduce

   Allreduce( &value, 1, op, group );

   // return the reduced value

   return value;

}

} // namespace MPI

} // namespace TNL