compileTimeTraversalLogic.hpp

/*
 * CoDiPack, a Code Differentiation Package
 *
 * Copyright (C) 2015-2025 Chair for Scientific Computing (SciComp), University of Kaiserslautern-Landau
 * Homepage: http://scicomp.rptu.de
 * Contact:  Prof. Nicolas R. Gauger (codi@scicomp.uni-kl.de)
 *
 * Lead developers: Max Sagebaum, Johannes Blühdorn (SciComp, University of Kaiserslautern-Landau)
 *
 * This file is part of CoDiPack (http://scicomp.rptu.de/software/codi).
 *
 * CoDiPack is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * CoDiPack 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 General Public License for more details.
 * You should have received a copy of the GNU
 * General Public License along with CoDiPack.
 * If not, see <http://www.gnu.org/licenses/>.
 *
 * For other licensing options please contact us.
 *
 * Authors:
 *  - SciComp, University of Kaiserslautern-Landau:
 *    - Max Sagebaum
 *    - Johannes Blühdorn
 *    - Former members:
 *      - Tim Albring
 */
#pragma once
 
#include <utility>
 
#include "../../config.h"
#include "../../misc/compileTimeLoop.hpp"
#include "../../misc/macros.hpp"
#include "../../traits/misc/removeAll.hpp"
#include "nodeInterface.hpp"

namespace codi {

  template<typename T_ResultType, typename T_Impl>
  struct CompileTimeTraversalLogic {
    public:
 
      using ResultType = CODI_DD(T_ResultType, size_t);         
      using Impl = CODI_DD(T_Impl, CompileTimeTraversalLogic);  
 
      static ResultType constexpr NeutralElement = {};  

      template<typename Node, typename... Args>
      CODI_INLINE static ResultType constexpr eval(Args&&... args) {
        return toNode<Node>(std::forward<Args>(args)...);
      }
 
      /*******************************************************************************/

      CODI_INLINE static ResultType constexpr reduce(ResultType a, ResultType b) {
        return a + b;
      }

      template<typename Node, typename... Args>
      CODI_INLINE static ResultType constexpr node(Args&&... args) {
        // Default logic forwards to all links.
        return Impl::template toLinks<Node>(std::forward<Args>(args)...);
      }

      template<typename Node, typename... Args>
      CODI_INLINE static ResultType constexpr leaf(Args&&... CODI_UNUSED_ARG(args)) {
        // Default logic does nothing.
        return Impl::NeutralElement;
      }

      template<size_t ChildNumber, typename Child, typename Root, typename... Args>
      CODI_INLINE static ResultType constexpr link(Args&&... args) {
        // Default logic forwards to node evaluation.
        return Impl::template toNode<Child>(std::forward<Args>(args)...);
      }

 
    protected:
 
#ifndef DOXYGEN_DISABLE
      template<typename TraversalImpl, bool endPoint = false>
      struct CallSwitch {
        public:
          template<typename Node, typename... Args>
          CODI_INLINE static ResultType constexpr call(Args&&... args) {
            return TraversalImpl::template node<Node>(std::forward<Args>(args)...);
          }
      };
 
      template<typename TraversalImpl>
      struct CallSwitch<TraversalImpl, true> {
        public:
          template<typename Node, typename... Args>
          CODI_INLINE static ResultType constexpr call(Args&&... args) {
            return TraversalImpl::template leaf<Node>(std::forward<Args>(args)...);
          }
      };
#endif

      template<typename Node, typename... Args>
      CODI_INLINE static ResultType constexpr toNode(Args&&... args) {
        return CallSwitch < Impl, 0 == Node::LinkCount > ::template call<Node>(std::forward<Args>(args)...);
      }
 
    private:
 
      // Reduce variadic for just one argument.
      template<typename Arg1>
      CODI_INLINE static ResultType constexpr reduceVariadic(Arg1&& arg1) {
        return arg1;
      }
 
      // Recursively calls reduceVariadic on the remainder and reduces the result with Impl::reduce together with
      // the first argument.
      template<typename Arg1, typename... Args>
      CODI_INLINE static ResultType constexpr reduceVariadic(Arg1&& arg1, Args&&... args) {
        return Impl::reduce(std::forward<Arg1>(arg1), reduceVariadic(std::forward<Args>(args)...));
      }
 
      // Expands the index sequence with the argument type of the getLink method from the Node. Calls reduceVariadic
      // with all arguments.
      template<typename Node, std::size_t... Is, typename... Args>
      CODI_INLINE static ResultType constexpr toLinksImpl(std::index_sequence<Is...>, Args&&... args) {
        return reduceVariadic(
            Impl::template link<Is, remove_all<decltype(std::declval<Node>().template getLink<Is>())>, Node>(
                std::forward<Args>(args)...)...);
      }
 
    public:

      template<typename Node, typename... Args>
      CODI_INLINE static ResultType constexpr toLinks(Args&&... args) {
        return toLinksImpl<Node>(std::make_index_sequence<Node::LinkCount>(), std::forward<Args>(args)...);
      }
  };
}