``MaxFirstLoc``
===============

.. role:: cpp(code)
    :language: cpp

Specific implementation of `ReducerConcept <ReducerConcept.html>`_ storing the maximum value and the first index satisfying a condition.

Header File: ``<Kokkos_Core.hpp>``

Usage
-----

.. code-block:: cpp

   MaxFirstLoc<T,I,S>::value_type result;
   parallel_reduce(N,Functor,MaxFirstLoc<T,I,S>(result));

Synopsis
--------

.. code-block:: cpp

   template<class Scalar, class Index, class Space>
   class MaxFirstLoc{
     public:
       using reducer = MaxFirstLoc;
       using value_type = ValLocScalar<typename std::remove_cv<Scalar>::type,
                               typename std::remove_cv<Index>::type>;
       using result_view_type = Kokkos::View<value_type, Space>;

       KOKKOS_INLINE_FUNCTION
       void join(value_type& dest, const value_type& src) const;

       KOKKOS_INLINE_FUNCTION
       void init(value_type& val) const;

       KOKKOS_INLINE_FUNCTION
       value_type& reference() const;

       KOKKOS_INLINE_FUNCTION
       result_view_type view() const;

       KOKKOS_INLINE_FUNCTION
       MaxFirstLoc(value_type& value_);

       KOKKOS_INLINE_FUNCTION
       MaxFirstLoc(const result_view_type& value_);
   };

Interface
---------

.. cpp:class:: template<class Scalar, class Index, class Space> MaxFirstLoc

   .. rubric:: Public Types

   .. cpp:type:: reducer

      The self type.

   .. cpp:type:: value_type

      The reduction scalar type (specialization of `ValLocScalar <ValLocScalar.html>`_)

   .. cpp:type:: result_view_type

      A ``Kokkos::View`` referencing the reduction result

   .. rubric:: Constructors

   .. cpp:function:: KOKKOS_INLINE_FUNCTION MaxFirstLoc(value_type& value_);

      Constructs a reducer which references a local variable as its result location.

   .. cpp:function:: KOKKOS_INLINE_FUNCTION MaxFirstLoc(const result_view_type& value_);

      Constructs a reducer which references a specific view as its result location.

   .. rubric:: Public Member Functions

   .. cpp:function:: KOKKOS_INLINE_FUNCTION void join(value_type& dest, const value_type& src) const;

      Store maximum with the first index of ``src`` and ``dest`` into ``dest``: ``dest = (src.val > dest.val) ? src :dest;``.

   .. cpp:function:: KOKKOS_INLINE_FUNCTION void init(value_type& val) const;

      Initialize ``val.val`` using the ``Kokkos::reduction_identity<Scalar>::max()`` method. The default implementation sets ``val=<TYPE>_MIN``.
      Initialize ``val.loc`` using the ``Kokkos::reduction_identity<Index>::min()`` method. The default implementation sets ``val=<TYPE>_MAX``.

   .. cpp:function:: KOKKOS_INLINE_FUNCTION value_type& reference() const;

      Returns a reference to the result provided in the class constructor.

   .. cpp:function:: KOKKOS_INLINE_FUNCTION result_view_type view() const;

      Returns a view of the result provided in the class constructor.

Additional Information
^^^^^^^^^^^^^^^^^^^^^^

* ``MaxFirstLoc<T,I,S>::result_view_type`` is ``Kokkos::View<T,S,Kokkos::MemoryTraits<Kokkos::Unmanaged>>``. Note that the S (memory space) must be the same as the space where the result resides.

* Requires: ``Scalar`` has ``operator =`` and ``operator >`` defined. ``Kokkos::reduction_identity<Scalar>::max()`` is a valid expression.

* Requires: ``Index`` has ``operator =`` defined. ``Kokkos::reduction_identity<Index>::min()`` is a valid expression.

* In order to use ``MaxFirstLoc`` with a custom type of either ``Scalar`` or ``Index``, a template specialization of ``Kokkos::reduction_identity<CustomType>`` must be defined. See `Built-In Reducers with Custom Scalar Types <../../../ProgrammingGuide/Custom-Reductions-Built-In-Reducers-with-Custom-Scalar-Types.html>`_ for details