src/analysis_tools.cpp


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#include "analysis_tools.hpp"

std::pair<std::array<unsigned, 2>, std::set<unsigned>> find_minimal_crack(const network& n, unsigned i0) {
  std::set<unsigned> removed_edges = n.get_cycle_edges(n.G.dual_edges[i0].v[0]);

  std::vector<std::pair<std::array<unsigned, 2>, std::set<unsigned>>> cycles;
  cycles.reserve(removed_edges.size());

  for (unsigned edge : removed_edges) {
    cycles.push_back(n.get_cycle(removed_edges, n.G.dual_edges[edge].v[0], n.G.dual_edges[edge].v[1])); 
    cycles.back().second.insert(edge);
    if (n.G.dual_edges[edge].crossings[0])
      cycles.back().first[0]++;
    if (n.G.dual_edges[edge].crossings[1])
      cycles.back().first[1]++;
  }

  if (cycles.size() == 1) {
    return cycles.front();
  }

  bool all_good = true;
  unsigned not_good;
  for (unsigned i = 0; i < 2; i++) {
    if (!((cycles[i].first[0] % 2 == 0 && cycles[i].first[1] % 2 == 1) || (cycles[i].first[0] % 2 == 1 && cycles[i].first[1] % 2 == 0))) {
      all_good = false;
      not_good = i;
    }
  }

  if (all_good) {
    if (cycles[0].second.size() > cycles[1].second.size()) {
      return cycles[1];
    } else {
      return cycles[0];
    }
  }

  const auto& cycle1 = cycles[0];
  const auto& cycle2 = cycles[1];

  unsigned sum_sig_0 = cycle1.first[0] + cycle2.first[0];
  unsigned sum_sig_1 = cycle1.first[1] + cycle2.first[1];

  std::valarray<uint8_t> bool_cycle1(n.G.edges.size());
  std::valarray<uint8_t> bool_cycle2(n.G.edges.size());
  for (auto v : cycle1.second) {
    bool_cycle1[v] = 1;
  }
  for (auto v : cycle2.second) {
    bool_cycle2[v] = 1;
  }

  std::valarray<uint8_t> new_bool_cycle = bool_cycle1 ^ bool_cycle2;

  std::set<unsigned> new_cycle;
  unsigned pos = 0;
  for (uint8_t included : new_bool_cycle) {
    if (included) {
      new_cycle.insert(pos);
    }
    pos++;
  }

  if (cycles[!not_good].second.size() > new_cycle.size()) {
    return {{sum_sig_0, sum_sig_1}, new_cycle};
  } else {
    return cycles[!not_good];
  }
}