Sacado_ELRFad_Expression.hpp

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// @HEADER
// *****************************************************************************
//                           Sacado Package
//
// Copyright 2006 NTESS and the Sacado contributors.
// SPDX-License-Identifier: LGPL-2.1-or-later
//
// ***********************************************************************
//
// The forward-mode AD classes in Sacado are a derivative work of the
// expression template classes in the Fad package by Nicolas Di Cesare.
// The following banner is included in the original Fad source code:
//
// ************ DO NOT REMOVE THIS BANNER ****************
//
//  Nicolas Di Cesare <Nicolas.Dicesare@ann.jussieu.fr>
//  http://www.ann.jussieu.fr/~dicesare
//
//            CEMRACS 98 : C++ courses,
//         templates : new C++ techniques
//            for scientific computing
//
//********************************************************
//
//  A short implementation ( not all operators and
//  functions are overloaded ) of 1st order Automatic
//  Differentiation in forward mode (FAD) using
//  EXPRESSION TEMPLATES.
//
//********************************************************
// @HEADER

#ifndef SACADO_ELRFAD_EXPRESSION_HPP
#define SACADO_ELRFAD_EXPRESSION_HPP

#include "Sacado_Traits.hpp"

namespace Sacado {

  namespace ELRFad {


    template <typename> struct BaseExpr {};


    template <typename ExprT>
    class Expr {};


    template <typename T>
    struct ExprLevel {
      static const unsigned value = 0;
    };

    template <typename T>
    struct ExprLevel< Expr<T> > {
      static const unsigned value =
        ExprLevel< typename Expr<T>::value_type >::value + 1;
    };

    template <typename T>
    struct IsFadExpr {
      static const bool value = false;
    };

    template <typename T>
    struct IsFadExpr< Expr<T> > {
      static const bool value = true;
    };


    template <typename ConstT>
    class ConstExpr {

    public:

      typedef ConstT value_type;

      typedef typename ScalarType<value_type>::type scalar_type;

      typedef ConstT base_expr_type;

      static const int num_args = 0;

      SACADO_INLINE_FUNCTION
      ConstExpr(const ConstT& constant) : constant_(constant) {}

      SACADO_INLINE_FUNCTION
      int size() const { return 0; }

      SACADO_INLINE_FUNCTION
      bool updateValue() const { return true; }

      SACADO_INLINE_FUNCTION
      value_type val() const { return constant_; }

      SACADO_INLINE_FUNCTION
      void computePartials(const value_type& bar,
                           value_type partials[]) const {}

      SACADO_INLINE_FUNCTION
      void getTangents(int i, value_type dots[]) const {}

      template <int Arg>
      SACADO_INLINE_FUNCTION
      value_type getTangent(int i) const { return 0.0; }

      template <int Arg>
      SACADO_INLINE_FUNCTION
      bool isActive() const { return false; }

      SACADO_INLINE_FUNCTION
      bool isLinear() const { return true; }

    protected:

      const ConstT& constant_;

    }; // class ConstExpr

    template <typename T> struct ExprConstRef {
      typedef const T& type;
    };
    template <typename T> struct ExprConstRef< ConstExpr<T> > {
      typedef const ConstExpr<T> type;
    };

  } // namespace ELRFad

  template <typename T>
  struct IsExpr< ELRFad::Expr<T> > {
    static const bool value = true;
  };

  template <typename T>
  struct BaseExprType< ELRFad::Expr<T> > {
    typedef typename ELRFad::Expr<T>::base_expr_type type;
  };

} // namespace Sacado

#include "Sacado_SFINAE_Macros.hpp"

#endif // SACADO_ELRFAD_EXPRESSION_HPP