parallelReuseIndexManager.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 <algorithm>
#include <vector>
 
#include "../../config.h"
#include "../../misc/macros.hpp"
#include "../../tools/parallel/parallelToolbox.hpp"
#include "reuseIndexManagerBase.hpp"

namespace codi {

  template<typename T_Index, typename T_ParallelToolbox>
  struct ParallelReuseIndexManager
      : public ReuseIndexManagerBase<T_Index, ParallelReuseIndexManager<T_Index, T_ParallelToolbox>> {
    public:
 
      using Index = CODI_DD(T_Index, int);  
      using ParallelToolbox = CODI_DD(T_ParallelToolbox,
                                      CODI_DEFAULT_PARALLEL_TOOLBOX);        
      using Base = ReuseIndexManagerBase<Index, ParallelReuseIndexManager>;  
      friend Base;  
 
    private:
 
      template<typename Type>
      using Atomic = typename ParallelToolbox::template Atomic<Type>;
 
      using ReadWriteMutex = typename ParallelToolbox::ReadWriteMutex;
 
    public:
 
      /*******************************************************************************/
 
      using Base::CopyNeedsStatement;                    
      using Base::IsLinear;                              
      static bool constexpr NeedsStaticStorage = false;  

 
    private:

      static CODI_NO_INLINE Atomic<T_Index>& globalMaximumIndex() {
        static Atomic<T_Index> _globalMaximumIndex;
        return _globalMaximumIndex;
      }

      static CODI_NO_INLINE bool& globalMaximumIndexInitialized() {
        static bool _globalMaximumIndexInitialized = false;
        return _globalMaximumIndexInitialized;
      }

      static CODI_NO_INLINE ReadWriteMutex& globalMaximumIndexMutex() {
        static ReadWriteMutex _globalMaximumIndexMutex;
        return _globalMaximumIndexMutex;
      }
 
    public:

      ParallelReuseIndexManager(Index const& reservedIndices) {
        globalMaximumIndexMutex().lockWrite();
        if (!globalMaximumIndexInitialized()) {
          globalMaximumIndex() = reservedIndices;
          globalMaximumIndexInitialized() = true;
        }
        globalMaximumIndexMutex().unlockWrite();
        generateNewIndices();
      }

      ~ParallelReuseIndexManager() {}
 
      /*******************************************************************************/

      void addToTapeValues(TapeValues& values) const {
        unsigned long maximumGlobalIndex = globalMaximumIndex();
 
        // As maximumGlobalIndex is static, it uses a local maximum reduction.
        TapeValues::LocalReductionOperation constexpr operation = TapeValues::LocalReductionOperation::Max;
 
        values.addUnsignedLongEntry("Max. live indices", maximumGlobalIndex, operation);
        // The number of current live indices cannot be computed from one instance alone.
        // It equals the number of maximum live indices minus the number of indices stored across all instances.
 
        Base::addToTapeValues(values);
      }

      CODI_INLINE Index getLargestCreatedIndex() const {
        return globalMaximumIndex();
      }

 
    private:
 
      CODI_NO_INLINE void generateNewIndices() {
        // This method is only called when unused indices are empty.
        // Initially, a number of unused indices is created which
        // equals the number of indices we generate now, therefore
        // we do not have to check for size.
 
        codiAssert(this->unusedIndices.size() >= this->indexSizeIncrement);
 
        Index upperIndexRangeBound = globalMaximumIndex() += this->indexSizeIncrement;  // note: atomic operation
        Index lowerIndexRangeBound = upperIndexRangeBound - this->indexSizeIncrement;
 
        for (size_t pos = 0; pos < this->indexSizeIncrement; ++pos) {
          this->unusedIndices[this->unusedIndicesPos + pos] = lowerIndexRangeBound + Index(pos) + 1;
        }
 
        this->unusedIndicesPos = this->indexSizeIncrement;
      }
  };
}