ParallelIIEstimator.ih

/**
 *  This program 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 3 of the
 *  License, or  (at your option) any later version.
 *
 *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 **/
 
/**
 * @file ParallelIIEstimator.ih
 * @author Bastien Doignies
 * Laboratoire d'InfoRmatique en Image et Systèmes d'information - LIRIS (CNRS, UMR 5205), INSA-Lyon, France
 *
 * @date 2026/05/01
 *
 * Header file for module ParallelEstimator.ih
 *
 * This file is part of the DGtal library.
 */
 
 
#include <deque>
#include <optional>
#include <ranges>
 
namespace DGtal
{
  template<class TEstimator, typename TSplitter>
  template<class... Args>
  ParallelIIEstimator<TEstimator, TSplitter>::
  ParallelIIEstimator(Splitter splitter, int32_t nbThread, Args&&... args)
    : mySplitter(std::move(splitter))
  {
      if (nbThread <= 0)
        nbThread = std::max(1, omp_get_max_threads());
 
      // Note: We can not use std::vector constructor or resize
      // because it will copy the estimator but it can have shared
      // state.
      // We rather build a new one in a loop by calling the constructor
      // implictely with emplace_back
      myEstimators.reserve(nbThread);
      for (int i = 0; i < nbThread; ++i)
        myEstimators.emplace_back(std::forward<Args>(args)...);
  }
 
  template<class TEstimator, typename TSplitter>
  void ParallelIIEstimator<TEstimator, TSplitter>::clear()
  {
    for (auto& estim : myEstimators)
      estim.clear();
  }
 
  template<class TEstimator, typename TSplitter>
  typename ParallelIIEstimator<TEstimator, TSplitter>::Scalar
  ParallelIIEstimator<TEstimator, TSplitter>::h() const { return myEstimators[0].h(); }
 
  template<class TEstimator, typename TSplitter>
  void ParallelIIEstimator<TEstimator, TSplitter>::attach(
      ConstAlias<KSpace> K,
      ConstAlias<PointPredicate> pp)
  {
    clear();
 
    myKSpace = K;
    myPointPredicate = pp;
  }
 
  template<class TEstimator, typename TSplitter>
  void ParallelIIEstimator<TEstimator, TSplitter>::setParams(double dRadius)
  {
    myRadius = dRadius;
  }
 
  template<class TEstimator, typename TSplitter>
  bool ParallelIIEstimator<TEstimator, TSplitter>::isValid() const
  {
    bool valid = true;
    for (const auto& estim : myEstimators)
      valid = valid && estim.isValid();
 
    return valid;
  }
 
  template<class TEstimator, typename TSplitter>
  template<typename ItA, typename ItB>
  void ParallelIIEstimator<TEstimator, TSplitter>::init(double h_, ItA, ItB)
  {
    myH = h_;
  }
 
  template<class TEstimator, typename TSplitter>
  template<typename It>
  typename ParallelIIEstimator<TEstimator, TSplitter>::Quantity
  ParallelIIEstimator<TEstimator, TSplitter>::eval(It it)
  {
    if (!myEstimators[0].isValid())
    {
      auto ite = it; ite++;
      myEstimators[0].init(myH, it, ite);
    }
 
    return {
      .location = *it,
      .value = myEstimators[0].eval(it)
    };
  }
 
  template<class TEstimator, typename TSplitter>
  template<typename It, typename Oit>
  Oit ParallelIIEstimator<TEstimator, TSplitter>::eval(It itb, It ite, Oit rslt)
  {
    Domain mainDomain(myKSpace->lowerBound(), myKSpace->upperBound());
    std::vector<SplitInfo<Domain>> domains = mySplitter(mainDomain, myEstimators.size());
 
    using Result = std::pair<Surfel, std::optional<EstimatorQuantity>>;
    std::deque<Result> result;
    std::vector<std::vector<Result*>> resultLocation(domains.size());
    for ( auto it = itb; it != ite; ++it )
    {
      result.push_back( { *it, std::nullopt } );
      Result* current = &result.back();
 
      for (unsigned int j = 0; j < domains.size(); ++j)
      {
        // Should be true for only one of the domain. The break ensure
        // each surfel belongs to one and only one domain, meaning there
        // will be no concurrent write afterward
        if (domains[j].domain.isInside(myKSpace->interiorVoxel(*it)))
        {
          resultLocation[j].push_back( current );
          break;
        }
      }
    }
 
    #pragma omp parallel for
    for (uint32_t i = 0; i < domains.size(); ++i)
    {
      auto surfels = resultLocation[i] | std::views::transform([](const auto* kv) -> const Surfel&
      {
        return kv->first;
      });
      auto values = resultLocation[i] | std::views::transform([](auto* kv) -> std::optional<EstimatorQuantity>&
      {
        return kv->second;
      });
 
      auto& estim = myEstimators[i];
 
      estim.attach(*myKSpace, *myPointPredicate);
      estim.setParams(myRadius);
 
      estim.init(myH, surfels.begin(), surfels.end());
      estim.eval(surfels.begin(), surfels.end(), values.begin());
    }
 
    for (const auto& entry : result)
    {
      assert(entry.second.has_value());
      *rslt++ = *entry.second;
    }
 
    return rslt;
  }
 
  template<class TEstimator, typename TSplitter>
  void
  ParallelIIEstimator<TEstimator, TSplitter>::selfDisplay( std::ostream & out ) const
  {
    out << "[ParallelIIEstimator Estim=";
    myEstimators[0].selfDisplay(out);
    out << "]";
  }
}