/* This file is part of the Gudhi Library. The Gudhi library
* (Geometric Understanding in Higher Dimensions) is a generic C++
* library for computational topology.
*
* Author(s): David Salinas
*
* Copyright (C) 2014 Inria
*
* This program 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.
*
* 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 .
*/
#ifndef SKELETON_BLOCKER_SIMPLIFIABLE_COMPLEX_H_
#define SKELETON_BLOCKER_SIMPLIFIABLE_COMPLEX_H_
#include
#include
#include
#include
namespace Gudhi {
namespace skeleton_blocker {
/**
* Returns true if the blocker 'sigma' is popable.
* To define popable, let us call 'L' the complex that
* consists in the current complex without the blocker 'sigma'.
* A blocker 'sigma' is then "popable" if the link of 'sigma'
* in L is reducible.
*
*/
template
bool Skeleton_blocker_complex::is_popable_blocker(Blocker_handle sigma) const {
assert(this->contains_blocker(*sigma));
Skeleton_blocker_link_complex link_blocker_sigma;
build_link_of_blocker(*this, *sigma, link_blocker_sigma);
return link_blocker_sigma.is_contractible() == CONTRACTIBLE;
}
/**
* Removes all the popable blockers of the complex and delete them.
* @returns the number of popable blockers deleted
*/
template
void Skeleton_blocker_complex::remove_popable_blockers() {
std::list vertex_to_check;
for (auto v : this->vertex_range())
vertex_to_check.push_front(v);
while (!vertex_to_check.empty()) {
Vertex_handle v = vertex_to_check.front();
vertex_to_check.pop_front();
bool blocker_popable_found = true;
while (blocker_popable_found) {
blocker_popable_found = false;
for (auto block : this->blocker_range(v)) {
if (this->is_popable_blocker(block)) {
for (Vertex_handle nv : *block)
if (nv != v) vertex_to_check.push_back(nv);
this->delete_blocker(block);
blocker_popable_found = true;
break;
}
}
}
}
}
/**
* Removes all the popable blockers of the complex passing through v and delete them.
*/
template
void Skeleton_blocker_complex::remove_popable_blockers(Vertex_handle v) {
bool blocker_popable_found = true;
while (blocker_popable_found) {
blocker_popable_found = false;
for (auto block : this->blocker_range(v)) {
if (is_popable_blocker(block)) {
this->delete_blocker(block);
blocker_popable_found = true;
}
}
}
}
/**
* @brief Removes all the popable blockers of the complex passing through v and delete them.
* Also remove popable blockers in the neighborhood if they became popable.
*
*/
template
void Skeleton_blocker_complex::remove_all_popable_blockers(Vertex_handle v) {
std::list vertex_to_check;
vertex_to_check.push_front(v);
while (!vertex_to_check.empty()) {
Vertex_handle v = vertex_to_check.front();
vertex_to_check.pop_front();
bool blocker_popable_found = true;
while (blocker_popable_found) {
blocker_popable_found = false;
for (auto block : this->blocker_range(v)) {
if (this->is_popable_blocker(block)) {
for (Vertex_handle nv : *block)
if (nv != v) vertex_to_check.push_back(nv);
this->delete_blocker(block);
blocker_popable_found = true;
break;
}
}
}
}
}
/**
* Remove the star of the vertice 'v'
*/
template
void Skeleton_blocker_complex::remove_star(Vertex_handle v) {
// we remove the blockers that are not consistent anymore
update_blockers_after_remove_star_of_vertex_or_edge(Simplex(v));
while (this->degree(v) > 0) {
Vertex_handle w(* (adjacent_vertices(v.vertex, this->skeleton).first));
this->remove_edge(v, w);
}
this->remove_vertex(v);
}
/**
* after removing the star of a simplex, blockers sigma that contains this simplex must be removed.
* Furthermore, all simplices tau of the form sigma \setminus simplex_to_be_removed must be added
* whenever the dimension of tau is at least 2.
*/
template
void Skeleton_blocker_complex::update_blockers_after_remove_star_of_vertex_or_edge(const Simplex& simplex_to_be_removed) {
std::list blockers_to_update;
if (simplex_to_be_removed.empty()) return;
auto v0 = simplex_to_be_removed.first_vertex();
for (auto blocker : this->blocker_range(v0)) {
if (blocker->contains(simplex_to_be_removed))
blockers_to_update.push_back(blocker);
}
for (auto blocker_to_update : blockers_to_update) {
Simplex sub_blocker_to_be_added;
bool sub_blocker_need_to_be_added =
(blocker_to_update->dimension() - simplex_to_be_removed.dimension()) >= 2;
if (sub_blocker_need_to_be_added) {
sub_blocker_to_be_added = *blocker_to_update;
sub_blocker_to_be_added.difference(simplex_to_be_removed);
}
this->delete_blocker(blocker_to_update);
if (sub_blocker_need_to_be_added)
this->add_blocker(sub_blocker_to_be_added);
}
}
/**
* Remove the star of the edge connecting vertices a and b.
* @returns the number of blocker that have been removed
*/
template
void Skeleton_blocker_complex::remove_star(Vertex_handle a, Vertex_handle b) {
update_blockers_after_remove_star_of_vertex_or_edge(Simplex(a, b));
// we remove the edge
this->remove_edge(a, b);
}
/**
* Remove the star of the edge 'e'.
*/
template
void Skeleton_blocker_complex::remove_star(Edge_handle e) {
return remove_star(this->first_vertex(e), this->second_vertex(e));
}
/**
* Remove the star of the simplex 'sigma' which needs to belong to the complex
*/
template
void Skeleton_blocker_complex::remove_star(const Simplex& sigma) {
assert(this->contains(sigma));
if (sigma.dimension() == 0) {
remove_star(sigma.first_vertex());
} else if (sigma.dimension() == 1) {
remove_star(sigma.first_vertex(), sigma.last_vertex());
} else {
remove_blocker_containing_simplex(sigma);
this->add_blocker(sigma);
}
}
template
void Skeleton_blocker_complex::add_simplex(const Simplex& sigma) {
// to add a simplex s, all blockers included in s are first removed
// and then all simplex in the coboundary of s are added as blockers
assert(!this->contains(sigma));
assert(sigma.dimension() > 1);
if (!contains_vertices(sigma)) {
std::cerr << "add_simplex: Some vertices were not present in the complex, adding them" << std::endl;
size_t num_vertices_to_add = sigma.last_vertex() - this->num_vertices() + 1;
for (size_t i = 0; i < num_vertices_to_add; ++i)
this->add_vertex();
}
assert(contains_vertices(sigma));
if (!contains_edges(sigma))
add_edge(sigma);
remove_blocker_include_in_simplex(sigma);
add_blockers_after_simplex_insertion(sigma);
}
template
void Skeleton_blocker_complex::add_blockers_after_simplex_insertion(Simplex sigma) {
if (sigma.dimension() < 1) return;
for (auto s : coboundary_range(sigma)) {
this->add_blocker(s);
}
}
/**
* remove all blockers that contains sigma
*/
template
void Skeleton_blocker_complex::remove_blocker_containing_simplex(const Simplex& sigma) {
std::vector blockers_to_remove;
for (auto blocker : this->blocker_range(sigma.first_vertex())) {
if (blocker->contains(sigma))
blockers_to_remove.push_back(blocker);
}
for (auto blocker_to_update : blockers_to_remove)
this->delete_blocker(blocker_to_update);
}
/**
* remove all blockers that contains sigma
*/
template
void Skeleton_blocker_complex::remove_blocker_include_in_simplex(const Simplex& sigma) {
// TODO(DS): write efficiently by using only superior blockers
// eg for all s, check blockers whose vertices are all greater than s
std::set blockers_to_remove;
for (auto s : sigma) {
for (auto blocker : this->blocker_range(s)) {
if (sigma.contains(*blocker))
blockers_to_remove.insert(blocker);
}
}
for (auto blocker_to_update : blockers_to_remove) {
auto s = *blocker_to_update;
this->delete_blocker(blocker_to_update);
// now if there is a vertex v in the link of s
// and v is not included in sigma then v.s is a blocker
// (all faces of v.s are there since v belongs to the link of s)
for (const auto& b : coboundary_range(s))
if (!sigma.contains(b))
this->add_blocker(b);
}
}
/**
* Compute simplices beta such that a.beta is an order 0 blocker
* that may be used to construct a new blocker after contracting ab.
* It requires that the link condition is satisfied.
*/
template
void Skeleton_blocker_complex::tip_blockers(Vertex_handle a, Vertex_handle b,
std::vector & buffer) const {
for (auto const & blocker : this->const_blocker_range(a)) {
Simplex beta = (*blocker);
beta.remove_vertex(a);
buffer.push_back(beta);
}
Simplex n;
this->add_neighbours(b, n);
this->remove_neighbours(a, n);
n.remove_vertex(a);
for (Vertex_handle y : n) {
Simplex beta;
beta.add_vertex(y);
buffer.push_back(beta);
}
}
/**
* @brief "Replace" the edge 'bx' by the edge 'ax'.
* Assume that the edge 'bx' was present whereas 'ax' was not.
* Precisely, it does not replace edges, but remove 'bx' and then add 'ax'.
* The visitor 'on_swaped_edge' is called just after edge 'ax' had been added
* and just before edge 'bx' had been removed. That way, it can
* eventually access to information of 'ax'.
*/
template
void
Skeleton_blocker_complex::swap_edge(Vertex_handle a, Vertex_handle b, Vertex_handle x) {
this->add_edge_without_blockers(a, x);
if (this->visitor) this->visitor->on_swaped_edge(a, b, x);
this->remove_edge(b, x);
}
template
void
Skeleton_blocker_complex::delete_blockers_around_vertex(Vertex_handle v) {
std::list blockers_to_delete;
for (auto blocker : this->blocker_range(v)) {
blockers_to_delete.push_back(blocker);
}
while (!blockers_to_delete.empty()) {
this->remove_blocker(blockers_to_delete.back());
blockers_to_delete.pop_back();
}
}
/**
* @brief removes all blockers passing through the edge 'ab'
*/
template
void
Skeleton_blocker_complex::delete_blockers_around_edge(Vertex_handle a, Vertex_handle b) {
std::list blocker_to_delete;
for (auto blocker : this->blocker_range(a))
if (blocker->contains(b)) blocker_to_delete.push_back(blocker);
while (!blocker_to_delete.empty()) {
this->delete_blocker(blocker_to_delete.back());
blocker_to_delete.pop_back();
}
}
/**
* Contracts the edge connecting vertices a and b.
* @remark If the link condition Link(ab) = Link(a) inter Link(b) is not satisfied,
* it removes first all blockers passing through 'ab'
*/
template
void
Skeleton_blocker_complex::contract_edge(Vertex_handle a, Vertex_handle b) {
assert(this->contains_vertex(a));
assert(this->contains_vertex(b));
if (this->contains_edge(a, b))
this->add_edge_without_blockers(a, b);
// if some blockers passes through 'ab', we need to remove them.
if (!link_condition(a, b))
delete_blockers_around_edge(a, b);
std::set blockers_to_add;
get_blockers_to_be_added_after_contraction(a, b, blockers_to_add);
delete_blockers_around_vertices(a, b);
update_edges_after_contraction(a, b);
this->remove_vertex(b);
notify_changed_edges(a);
for (auto block : blockers_to_add)
this->add_blocker(block);
assert(this->contains_vertex(a));
assert(!this->contains_vertex(b));
}
template
void Skeleton_blocker_complex::get_blockers_to_be_added_after_contraction(Vertex_handle a,
Vertex_handle b,
std::set& blockers_to_add) {
blockers_to_add.clear();
typedef Skeleton_blocker_link_complex > LinkComplexType;
LinkComplexType link_a(*this, a);
LinkComplexType link_b(*this, b);
std::vector vector_alpha, vector_beta;
tip_blockers(a, b, vector_alpha);
tip_blockers(b, a, vector_beta);
for (auto alpha = vector_alpha.begin(); alpha != vector_alpha.end(); ++alpha) {
for (auto beta = vector_beta.begin(); beta != vector_beta.end(); ++beta) {
Simplex sigma = *alpha;
sigma.union_vertices(*beta);
Root_simplex_handle sigma_id = this->get_id(sigma);
if (this->contains(sigma) &&
proper_faces_in_union> (sigma_id, link_a, link_b)) {
// Blocker_handle blocker = new Simplex(sigma);
sigma.add_vertex(a);
blockers_to_add.insert(sigma);
}
}
}
}
/**
* delete all blockers that passes through a or b
*/
template
void
Skeleton_blocker_complex::delete_blockers_around_vertices(Vertex_handle a, Vertex_handle b) {
std::vector blocker_to_delete;
for (auto bl : this->blocker_range(a))
blocker_to_delete.push_back(bl);
for (auto bl : this->blocker_range(b))
blocker_to_delete.push_back(bl);
while (!blocker_to_delete.empty()) {
this->delete_blocker(blocker_to_delete.back());
blocker_to_delete.pop_back();
}
}
template
void
Skeleton_blocker_complex::update_edges_after_contraction(Vertex_handle a, Vertex_handle b) {
// We update the set of edges
this->remove_edge(a, b);
// For all edges {b,x} incident to b,
// we remove {b,x} and add {a,x} if not already there.
while (this->degree(b) > 0) {
Vertex_handle x(*(adjacent_vertices(b.vertex, this->skeleton).first));
if (!this->contains_edge(a, x))
// we 'replace' the edge 'bx' by the edge 'ax'
this->swap_edge(a, b, x);
else
this->remove_edge(b, x);
}
}
template
void
Skeleton_blocker_complex::notify_changed_edges(Vertex_handle a) {
// We notify the visitor that all edges incident to 'a' had changed
boost_adjacency_iterator v, v_end;
for (tie(v, v_end) = adjacent_vertices(a.vertex, this->skeleton); v != v_end; ++v)
if (this->visitor) this->visitor->on_changed_edge(a, Vertex_handle(*v));
}
} // namespace skeleton_blocker
namespace skbl = skeleton_blocker;
} // namespace Gudhi
#endif // SKELETON_BLOCKER_SIMPLIFIABLE_COMPLEX_H_