path: root/lib/src/network.cpp

#include "network.hpp"

class nanException: public std::exception
{
  virtual const char* what() const throw()
  {
    return "The linear problem returned NaN.";
  }
} nanex;

class nofuseException: public std::exception
{
  virtual const char* what() const throw()
  {
    return "No valid fuse was available to break.";
  }
} nofuseex;

network::network(const graph& G, cholmod_common *c) : c(c), G(G), fuses(G.edges.size(), false), thresholds(G.edges.size(), 1) {
  b = CHOL_F(zeros)(G.vertices.size(), 1, CHOLMOD_REAL, c);
  for (unsigned i = 0; i < G.edges.size(); i++) {
    double v0y = G.vertices[G.edges[i].v[0]].r.y;
    double v1y = G.vertices[G.edges[i].v[1]].r.y;

    if (G.edges[i].crossings[1]) {
      bool ind = v0y < v1y ? 0 : 1;

      ((double *)b->x)[G.edges[i].v[ind]] += 1.0;
      ((double *)b->x)[G.edges[i].v[!ind]] -= 1.0;
    }
  }

  unsigned nnz = G.vertices.size() + G.edges.size();

  cholmod_triplet *t = CHOL_F(allocate_triplet)(G.vertices.size(), G.vertices.size(), nnz,  1, CHOLMOD_REAL, c);

  for (unsigned i = 0; i < G.vertices.size(); i++) {
    ((CHOL_INT *)t->i)[i] = i;
    ((CHOL_INT *)t->j)[i] = i;
    ((double *)t->x)[i] = 0.0;
  }

  unsigned terms = G.vertices.size();

  std::unordered_map<std::array<unsigned, 2>, unsigned> known_edges;

  for (unsigned i = 0; i < G.edges.size(); i++) {
    unsigned v0 = G.edges[i].v[0];
    unsigned v1 = G.edges[i].v[1];

    ((double *)t->x)[v0]++;
    ((double *)t->x)[v1]++;

    unsigned s0 = v0 < v1 ? v0 : v1;
    unsigned s1 = v0 < v1 ? v1 : v0;

    auto it = known_edges.find({s0, s1});

    if (it == known_edges.end()) {
      ((CHOL_INT *)t->i)[terms] = s1;
      ((CHOL_INT *)t->j)[terms] = s0;
      ((double *)t->x)[terms] = -1.0;

      known_edges[{s0, s1}] = terms;
      terms++;
    } else {
      ((double *)t->x)[it->second] -= 1.0;
    }
  }

  ((double *)t->x)[0]++;

  t->nnz = terms;

  cholmod_sparse *laplacian = CHOL_F(triplet_to_sparse)(t, terms, c);
  CHOL_F(free_triplet)(&t, c);
  factor = CHOL_F(analyze)(laplacian, c);
  CHOL_F(factorize)(laplacian, factor, c);
  CHOL_F(free_sparse)(&laplacian, c);

  t = CHOL_F(allocate_triplet)(G.edges.size(), G.vertices.size(), 2 * G.edges.size(), 0, CHOLMOD_REAL, c);

  t->nnz = 2 * G.edges.size();

  for (unsigned i = 0; i < G.edges.size(); i++) {
    ((CHOL_INT *)t->i)[2 * i] = i;
    ((CHOL_INT *)t->j)[2 * i] = G.edges[i].v[0];
    ((double *)t->x)[2 * i] = 1.0;

    ((CHOL_INT *)t->i)[2 * i + 1] = i;
    ((CHOL_INT *)t->j)[2 * i + 1] = G.edges[i].v[1];
    ((double *)t->x)[2 * i + 1] = -1.0;
  }

  voltcurmat = CHOL_F(triplet_to_sparse)(t, 2 * G.edges.size(), c);

  CHOL_F(free_triplet)(&t, c);
}

network::network(const network &other) : c(other.c), G(other.G), fuses(other.fuses), thresholds(other.thresholds) {
  b = CHOL_F(copy_dense)(other.b, c);
  factor = CHOL_F(copy_factor)(other.factor, c);
  voltcurmat = CHOL_F(copy_sparse)(other.voltcurmat, c);
} 

network::~network() {
  CHOL_F(free_sparse)(&voltcurmat, c);
  CHOL_F(free_dense)(&b, c);
  CHOL_F(free_factor)(&factor, c);
}

void network::set_thresholds(double beta, std::mt19937& rng) {
  if (beta == 0.0) {
    /* zero beta doesn't make any sense computationally, we interpret it as "infinity" */
    for (long double& threshold : thresholds) {
      threshold = 1.0;
    }
  } else {
    std::uniform_real_distribution<long double> d(0.0, 1.0);

    for (long double& threshold : thresholds) {
      threshold = std::numeric_limits<long double>::lowest();

      while (threshold == std::numeric_limits<long double>::lowest()) {
        threshold = logl(d(rng)) / (long double)beta;
      }
    }
  }
}

void network::break_edge(unsigned e, bool unbreak) {
  fuses[e] = !unbreak;
  unsigned v0 = G.edges[e].v[0];
  unsigned v1 = G.edges[e].v[1];

  unsigned n = factor->n;

  cholmod_sparse *update_mat = CHOL_F(allocate_sparse)(n, n, 2, true, true, 0, CHOLMOD_REAL, c);

  unsigned s1, s2;
  s1 = v0 < v1 ? v0 : v1;
  s2 = v0 < v1 ? v1 : v0;

  CHOL_INT *pp = (CHOL_INT *)update_mat->p;
  CHOL_INT *ii = (CHOL_INT *)update_mat->i;
  double *xx = (double *)update_mat->x;

  for (unsigned i = 0; i <= s1; i++) {
    pp[i] = 0;
  }

  for (unsigned i = s1 + 1; i <= n; i++) {
    pp[i] = 2;
  }

  ii[0] = s1;
  ii[1] = s2;
  xx[0] = 1;
  xx[1] = -1;

  cholmod_sparse *perm_update_mat = CHOL_F(submatrix)(
      update_mat, (CHOL_INT *)factor->Perm, factor->n, NULL, -1, true, true, c);

  CHOL_F(updown)(unbreak, perm_update_mat, factor, c);

  CHOL_F(free_sparse)(&perm_update_mat, c);
  CHOL_F(free_sparse)(&update_mat, c);

  double v0y = G.vertices[v0].r.y;
  double v1y = G.vertices[v1].r.y;

  if (G.edges[e].crossings[1]) {
    bool ind = v0y < v1y ? unbreak : !unbreak;

    ((double *)b->x)[G.edges[e].v[ind]] -= 1.0;
    ((double *)b->x)[G.edges[e].v[!ind]] += 1.0;
  }
}

current_info network::get_current_info() {
  cholmod_dense *x = CHOL_F(solve)(CHOLMOD_A, factor, b, c);

  if (((double *)x->x)[0] != ((double *)x->x)[0]) {
    throw nanex;
  }

  cholmod_dense *y = CHOL_F(allocate_dense)(G.edges.size(), 1, G.edges.size(), CHOLMOD_REAL, c);

  double alpha[2] = {1, 0};
  double beta[2] = {0, 0};
  CHOL_F(sdmult)(voltcurmat, 0, alpha, beta, x, y, c);

  std::vector<double> currents(G.edges.size());

  double total_current = 0;

  for (int i = 0; i < G.edges.size(); i++) {
    if (fuses[i]) {
      currents[i] = 0;
    } else {
      currents[i] = ((double *)y->x)[i];

      double v0y = G.vertices[G.edges[i].v[0]].r.y;
      double v1y = G.vertices[G.edges[i].v[1]].r.y;

      if (G.edges[i].crossings[1]) {
        if (v0y > v1y) {
          currents[i] += 1.0;
          total_current += currents[i];
        } else {
          currents[i] -= 1.0;
          total_current -= currents[i];
        }
      }
    }

  }

  CHOL_F(free_dense)(&x, c);
  CHOL_F(free_dense)(&y, c);

  return {total_current, currents};
}

void network::fracture(hooks& m, double cutoff) {
  m.pre_fracture(*this);

  while (true) {
    current_info ci = this->get_current_info();

    if (ci.conductivity < cutoff * G.vertices.size()) {
      break;
    }

    unsigned max_pos = UINT_MAX;
    long double max_val = std::numeric_limits<long double>::lowest();

    for (unsigned i = 0; i < G.edges.size(); i++) {
      if (!fuses[i] && fabs(ci.currents[i]) > cutoff) {
        long double val = logl(fabs(ci.currents[i])) - thresholds[i];
        if (val > max_val) {
          max_val = val;
          max_pos = i;
        }
      }
    }

    if (max_pos == UINT_MAX)  {
      throw nofuseex;
    }

    this->break_edge(max_pos);

    m.bond_broken(*this, ci, max_pos);
  }

  m.post_fracture(*this);
}