Sacado_ELRFad_Expression.hpp

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// $Id: Sacado_ELRFad_Expression.hpp,v 1.1.2.2 2007/09/18 18:42:13 rabartl Exp $ 
// $Source: /space/CVS/Trilinos/packages/sacado/src/Sacado_ELRFad_Expression.hpp,v $ 
// @HEADER
// ***********************************************************************
// 
//                           Sacado Package
//                 Copyright (2006) Sandia Corporation
// 
// Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
// the U.S. Government retains certain rights in this software.
// 
// This library is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; either version 2.1 of the
// License, or (at your option) any later version.
//  
// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//  
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
// USA
// Questions? Contact David M. Gay (dmgay@sandia.gov) or Eric T. Phipps
// (etphipp@sandia.gov).
// 
// ***********************************************************************
//
// 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 A, typename B> struct ExprPromote {};

    template <typename A> struct ExprPromote<A,A> {
      typedef A type;
    };


    template <typename ExprT> 
    class Expr {

    public:

      typedef typename ExprT::value_type value_type;

      typedef typename ExprT::base_expr_type base_expr_type;

      static const int num_args = ExprT::num_args;

      explicit Expr(const ExprT& expr) : expr_(expr) {}

      int size() const {return expr_.size();}

      value_type val() const { return expr_.val();}

      void computePartials(const value_type& bar, 
         value_type partials[]) const { 
  expr_.computePartials(bar, partials); }

      void getTangents(int i, value_type dots[]) const { 
  expr_.getTangents(i, dots); }

      template <int Arg>
      value_type getTangent(int i) const {
  return expr_.template getTangent<Arg>(i);
      }

      template <int Arg>
      bool isActive() const { return expr_.template isActive<Arg>(); }
      
    protected:

      Expr() {}

      ExprT expr_;

    }; // class Expr


    template <typename ConstT> 
    class ConstExpr {

    public:

      typedef ConstT value_type;

      typedef ConstT base_expr_type;

      static const int num_args = 0;

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

      int size() const { return 0; }

      value_type val() const { return constant_; }

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

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

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

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

    protected:
      
      const ConstT& constant_;

    }; // class ConstExpr


    template <typename ExprT, template<typename> class Op> 
    class UnaryExpr {

    public:

      typedef typename ExprT::value_type value_type;

      typedef typename ExprT::base_expr_type base_expr_type;

      typedef Op<ExprT> OpT;

      static const int num_args = ExprT::num_args;

      UnaryExpr(const ExprT& expr) : expr_(expr) {}

      int size() const { return expr_.size(); }

      value_type val() const { return OpT::computeValue(expr_); }

      void computePartials(const value_type& bar, 
         value_type partials[]) const { 
  expr_.computePartials(OpT::computeAdjoint(bar, expr_), partials); }

      void getTangents(int i, value_type dots[]) const { 
  expr_.getTangents(i, dots); }

      template <int Arg>
      value_type getTangent(int i) const {
  return expr_.template getTangent<Arg>(i);
      }

      template <int Arg>
      bool isActive() const { return expr_.template isActive<Arg>(); }

    protected:
      
      const ExprT& expr_;

    }; // class UnaryExpr

    // The Sun compiler has difficulty with class partial specialization and
    // template templates, which the original BinaryExpr classes below use.
    // However the only significant difference between the specializations
    // of BinaryExpr for constant arguments is removing the reference
    // for the corresponding data member.  The type functions below allow
    // us to do this without specializing BinaryExpr.  We could also 
    // remove the template templates, but that drastically increases
    // compile times due to the increased length of template argument lists.
    template <typename T> struct ExprConstRef {
      typedef const T& type;
    };
    template <typename T> struct ExprConstRef< ConstExpr<T> > {
      typedef const ConstExpr<T> type;
    };


    template <typename ExprT1, typename ExprT2, 
        template<typename,typename> class Op> 
    class BinaryExpr {
    
    public:

      typedef typename ExprT1::value_type value_type_1;

      typedef typename ExprT2::value_type value_type_2;

      typedef typename Sacado::Promote<value_type_1,
               value_type_2>::type value_type;

      typedef typename ExprT1::base_expr_type base_expr_type_1;

      typedef typename ExprT2::base_expr_type base_expr_type_2;

      typedef typename ExprPromote<base_expr_type_1,
           base_expr_type_2>::type base_expr_type;

      static const int num_args1 = ExprT1::num_args;

      static const int num_args2 = ExprT2::num_args;

      static const int num_args = num_args1 + num_args2;

      typedef Op<ExprT1,ExprT2> OpT;

      BinaryExpr(const ExprT1& expr1, const ExprT2& expr2) : 
  expr1_(expr1), expr2_(expr2) {}

      int size() const {
  int sz1 = expr1_.size(), sz2 = expr2_.size(); 
  return sz1 > sz2 ? sz1 : sz2;
      }

      void computePartials(const value_type& bar, 
         value_type partials[]) const { 
  if (num_args1 > 0)
    expr1_.computePartials(OpT::computeLeftAdjoint(bar, expr1_, expr2_), 
         partials);
  if (num_args2 > 0)
    expr2_.computePartials(OpT::computeRightAdjoint(bar, expr1_, expr2_),
         partials+num_args1);
      }

      void getTangents(int i, value_type dots[]) const { 
  expr1_.getTangents(i, dots); 
  expr2_.getTangents(i, dots+num_args1); }

      value_type val() const { 
  return OpT::computeValue(expr1_,expr2_); }

      template <int Arg>
      value_type getTangent(int i) const {
  if (Arg < num_args1)
    return expr1_.template getTangent<Arg>(i);
  else
    return expr2_.template getTangent<Arg-num_args1>(i);
      }

      template <int Arg>
      bool isActive() const { 
  if (Arg < num_args1)
    return expr1_.template isActive<Arg>(); 
  else
    return expr2_.template isActive<Arg-num_args1>();
      }

    protected:
      
      typename ExprConstRef<ExprT1>::type expr1_;

      typename ExprConstRef<ExprT2>::type expr2_;

    }; // class BinaryExpr

  } // namespace ELRFad

} // namespace Sacado

#endif // SACADO_ELRFAD_EXPRESSION_HPP

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