base_pairing.h

Go to the documentation of this file.

/*    This file is part of the Gudhi Library - https://gudhi.inria.fr/ - which is released under MIT.
 *    See file LICENSE or go to https://gudhi.inria.fr/licensing/ for full license details.
 *    Author(s):       Hannah Schreiber
 *
 *    Copyright (C) 2022-24 Inria
 *
 *    Modification(s):
 *      - YYYY/MM Author: Description of the modification
 */
 
#ifndef PM_BASE_PAIRING_H
#define PM_BASE_PAIRING_H
 
#include <utility>  //std::swap & std::move
#include <unordered_map>
#include <algorithm>
#include <vector>
 
#include "boundary_cell_position_to_id_mapper.h"
 
namespace Gudhi {
namespace persistence_matrix {
 
struct Dummy_base_pairing {
  friend void swap([[maybe_unused]] Dummy_base_pairing& d1, [[maybe_unused]] Dummy_base_pairing& d2) {}
};
 
template <class Master_matrix>
class Base_pairing : public std::conditional<
                       Master_matrix::Option_list::has_removable_columns,
                       Cell_position_to_ID_mapper<typename Master_matrix::ID_index, typename Master_matrix::Pos_index>,
                       Dummy_pos_mapper
                    >::type
{
 public:
  using Bar = typename Master_matrix::Bar;                            
  using Barcode = typename Master_matrix::Barcode;                    
  using Column_container = typename Master_matrix::Column_container;  
  using Index = typename Master_matrix::Index;                        
  using Dimension = typename Master_matrix::Dimension;                
  Base_pairing();
 
  const Barcode& get_current_barcode();
 
  friend void swap(Base_pairing& pairing1, Base_pairing& pairing2) {
    if constexpr (Master_matrix::Option_list::has_removable_columns) {
      swap(static_cast<Cell_position_to_ID_mapper<ID_index, Pos_index>&>(pairing1),
           static_cast<Cell_position_to_ID_mapper<ID_index, Pos_index>&>(pairing2));
    }
    pairing1.barcode_.swap(pairing2.barcode_);
    pairing1.deathToBar_.swap(pairing2.deathToBar_);
    pairing1.idToPosition_.swap(pairing2.idToPosition_);
    std::swap(pairing1.isReduced_, pairing2.isReduced_);
  }
 
 protected:
  using Pos_index = typename Master_matrix::Pos_index;
  using ID_index = typename Master_matrix::ID_index;
  using Dictionary = typename Master_matrix::Bar_dictionary;
  using Base_matrix = typename Master_matrix::Master_boundary_matrix;
  //PIDM = Position to ID Map
  using PIDM = typename std::conditional<Master_matrix::Option_list::has_removable_columns,
                                         Cell_position_to_ID_mapper<ID_index, Pos_index>,
                                         Dummy_pos_mapper
                                        >::type;
 
  Barcode barcode_;       
  Dictionary deathToBar_; 
  std::unordered_map<ID_index,Pos_index> idToPosition_;  //TODO: test other map types
  bool isReduced_;        
  void _reduce();
  void _remove_last(Pos_index columnIndex);
 
  //access to inheriting Boundary_matrix class
  constexpr Base_matrix* _matrix() { return static_cast<Base_matrix*>(this); }
  constexpr const Base_matrix* _matrix() const { return static_cast<const Base_matrix*>(this); }
};
 
template <class Master_matrix>
inline Base_pairing<Master_matrix>::Base_pairing() : PIDM(), isReduced_(false) 
{}
 
template <class Master_matrix>
inline const typename Base_pairing<Master_matrix>::Barcode& Base_pairing<Master_matrix>::get_current_barcode() 
{
  if (!isReduced_) _reduce();
  return barcode_;
}
 
template <class Master_matrix>
inline void Base_pairing<Master_matrix>::_reduce() 
{
  constexpr const Pos_index nullDeath = Master_matrix::template get_null_value<Pos_index>();
  constexpr const Index nullIndex = Master_matrix::template get_null_value<Index>();
 
  std::unordered_map<Index, Index> negativeColumns(_matrix()->get_number_of_columns());
 
  auto dim = _matrix()->get_max_dimension();
  std::vector<std::vector<Index> > columnsByDim(dim + 1);
  for (auto& v : columnsByDim) v.reserve(_matrix()->get_number_of_columns());
  for (unsigned int i = 0; i < _matrix()->get_number_of_columns(); i++) {
    columnsByDim[dim - _matrix()->get_column_dimension(i)].push_back(i);
  }
 
  for (const auto& cols : columnsByDim) {
    for (Index i : cols) {
      auto& curr = _matrix()->get_column(i);
      if (curr.is_empty()) {
        if (negativeColumns.find(i) == negativeColumns.end()) {
          barcode_.emplace_back(i, nullDeath, dim);
        }
      } else {
        ID_index pivot = curr.get_pivot();
        auto it = idToPosition_.find(pivot);
        Index pivotColumnNumber = it == idToPosition_.end() ? pivot : it->second;
        auto itNeg = negativeColumns.find(pivotColumnNumber);
        Index pivotKiller = itNeg == negativeColumns.end() ? nullIndex : itNeg->second;
 
        while (pivot != Master_matrix::template get_null_value<ID_index>() &&
               pivotKiller != Master_matrix::template get_null_value<Index>()) {
          if constexpr (Master_matrix::Option_list::is_z2) {
            curr += _matrix()->get_column(pivotKiller);
          } else {
            auto& toadd = _matrix()->get_column(pivotKiller);
            typename Master_matrix::Element coef = toadd.get_pivot_value();
            auto& operators = _matrix()->colSettings_->operators;
            coef = operators.get_inverse(coef);
            operators.multiply_inplace(coef, operators.get_characteristic() - curr.get_pivot_value());
            curr.multiply_source_and_add(toadd, coef);
          }
 
          pivot = curr.get_pivot();
          it = idToPosition_.find(pivot);
          pivotColumnNumber = it == idToPosition_.end() ? pivot : it->second;
          itNeg = negativeColumns.find(pivotColumnNumber);
          pivotKiller = itNeg == negativeColumns.end() ? nullIndex : itNeg->second;
        }
 
        if (pivot != Master_matrix::template get_null_value<ID_index>()) {
          negativeColumns.emplace(pivotColumnNumber, i);
          _matrix()->get_column(pivotColumnNumber).clear();
          barcode_.emplace_back(pivotColumnNumber, i, dim - 1);
        } else {
          curr.clear();
          barcode_.emplace_back(i, nullDeath, dim);
        }
      }
    }
    --dim;
  }
 
  if constexpr (Master_matrix::Option_list::has_removable_columns) {
    // sort barcode by birth such that a removal is trivial
    std::sort(barcode_.begin(), barcode_.end(), [](const Bar& b1, const Bar& b2) { return b1.birth < b2.birth; });
    // map can only be constructed once barcode is sorted
    for (Index i = 0; i < barcode_.size(); ++i) {
      auto d = barcode_[i].death;
      if (d != Master_matrix::template get_null_value<Pos_index>()) {
        deathToBar_.emplace(d, i);
      }
    }
  }
 
  isReduced_ = true;
}
 
template <class Master_matrix>
inline void Base_pairing<Master_matrix>::_remove_last(Pos_index columnIndex) 
{
  static_assert(Master_matrix::Option_list::has_removable_columns, "remove_last not available.");
 
  if (isReduced_) {
    auto it = deathToBar_.find(columnIndex);
 
    if (it == deathToBar_.end()) {  // birth
      barcode_.pop_back();          // sorted by birth and columnIndex has to be the highest one
    } else {                        // death
      barcode_[it->second].death = Master_matrix::template get_null_value<Pos_index>();
      deathToBar_.erase(it);
    };
  }
 
  auto it = PIDM::map_.find(columnIndex);
  if (it != PIDM::map_.end()){
    idToPosition_.erase(it->second);
    PIDM::map_.erase(it);
  }
}
 
}  // namespace persistence_matrix
}  // namespace Gudhi
 
#endif  // PM_BASE_PAIRING_H