Merging graphs using boost graph

Merging graphs using boost graph

By : hshasani
Date : November 24 2020, 03:41 PM
I think the issue was by ths following , First of all, we have to admit that the resulting graph is a SINGLE object. I assume you want it to be of the same type Graph as your original two graphs g1 and g2. It means you have a choice to do one of the following: Graph g = g1 + g2 or g1 += g2 (both choices are in pseudo-code, of course).
In any case, the result will contain a copy of the second graph, not the "original" object of the graph g2.
code :

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Comparing 2 graphs created by Boost Graph Library

Comparing 2 graphs created by Boost Graph Library

By : Brian Pedersen
Date : March 29 2020, 07:55 AM
I wish this help you Boost.Graph can do this but not with the == operator: http://www.boost.org/doc/libs/1_39_0/libs/graph/doc/isomorphism.html
It is a hard problem so it will take long for large graphs.
Find all linesegments=edges within a certain distance to a point in a graph, how to combine boost-graph with boost-geome

Find all linesegments=edges within a certain distance to a point in a graph, how to combine boost-graph with boost-geome

By : Mahmoud Hamdy
Date : March 29 2020, 07:55 AM
Hope this helps It is certainly possible to attach properties to linestrings in Boost.Geometry, actually Boost.Geometry is made for doing such things. You can just derive from boost::geometry::model::linestring, or implement any other range-based structure (e.g. std::vector) and register that as a linestring. See the c03 example.
For the relation with Boost.Graph, see one of the examples in Boost.Geometry: 07_a or 07_b where a similar thing is done. What is done there is storing a Boost.Geometry linestring into the Boost.Graph edge (with a property), together with other properties, so that is another way of doing this.
DFS in boost::graph with changing the graphs content

DFS in boost::graph with changing the graphs content

By : 이은미
Date : March 29 2020, 07:55 AM
With these it helps Have a look at how Boost implements connected_components. In order to store the component id the following visitor is used:
code :
// This visitor is used both in the connected_components algorithm
// and in the kosaraju strong components algorithm during the
// second DFS traversal.
template <class ComponentsMap>
class components_recorder : public dfs_visitor<>
  typedef typename property_traits<ComponentsMap>::value_type comp_type;
  components_recorder(ComponentsMap c, 
                      comp_type& c_count)
    : m_component(c), m_count(c_count) {}

  template <class Vertex, class Graph>
  void start_vertex(Vertex, Graph&) {
    if (m_count == (std::numeric_limits<comp_type>::max)())
      m_count = 0; // start counting components at zero
  template <class Vertex, class Graph>
  void discover_vertex(Vertex u, Graph&) {
    put(m_component, u, m_count);
  ComponentsMap m_component;
  comp_type& m_count;
template <class PropertyMap>
struct vertex_visitor : public boost::dfs_visitor<>
  PropertyMap m_pmap;
  vertex_visitor(PropertyMap pmap) : m_pmap(pmap) {}
  template <class Vertex, class Graph>
  void discover_vertex(Vertex v, const Graph& g)
    boost::put(m_pmap, v, 42);
typedef boost::property_map<graph_t, int vertex::*>::type NumbersProperty;
vertex_visitor<NumbersProperty> vis(boost::get(&vertex::number, g));
Graphs - Python - Store a graph db made of graphs - Graph db theory

Graphs - Python - Store a graph db made of graphs - Graph db theory

By : user2476288
Date : March 29 2020, 07:55 AM
will help you You did not label "J" in your diagram, so I will ignore it (and HELLO, whatever that is) in this answer.
code :
(foo:Subgraph {name: "Foo"})
(bar:Subgraph {name: "Bar"})
(world:Subgraph {name: "World"})


Boost Undirected Graph Merging Vertices

Boost Undirected Graph Merging Vertices

By : user3414526
Date : March 29 2020, 07:55 AM
I wish did fix the issue. I don't know what you're actually trying to achieve with the algorithm shown in the OP.
Here's, however, one that simplifies the code considerably, so that at least it works safely:
code :
#include <boost/graph/adjacency_list.hpp>
#include <iostream>

struct Vertex {
    int id;
    const char* name;

    Vertex(int i = -1, const char* name = "default") : id(i), name(name) {}

template <typename It> boost::iterator_range<It> mir(std::pair<It, It> const& p) {
    return boost::make_iterator_range(p.first, p.second);
template <typename It> boost::iterator_range<It> mir(It b, It e) {
    return boost::make_iterator_range(b, e);

typedef typename boost::adjacency_list<
        boost::vecS, boost::vecS,
        Vertex,                                      // bundled properties (id, name)
        boost::property<boost::edge_weight_t, float> // interior property
    > Graph;

Graph make() {
    Graph graph;

    auto Jeanie   = add_vertex(Vertex { 0, "Jeanie" },   graph);
    auto Debbie   = add_vertex(Vertex { 1, "Debbie" },   graph);
    auto Rick     = add_vertex(Vertex { 2, "Rick" },     graph);
    auto John     = add_vertex(Vertex { 3, "John" },     graph);
    auto Amanda   = add_vertex(Vertex { 4, "Amanda" },   graph);
    auto Margaret = add_vertex(Vertex { 5, "Margaret" }, graph);
    auto Benjamin = add_vertex(Vertex { 6, "Benjamin" }, graph);

    add_edge(Jeanie, Debbie,   0.5f, graph);
    add_edge(Jeanie, Rick,     0.2f, graph);
    add_edge(Jeanie, John,     0.1f, graph);
    add_edge(Debbie, Amanda,   0.3f, graph);
    add_edge(Rick,   Margaret, 0.4f, graph);
    add_edge(John,   Benjamin, 0.6f, graph);

    return graph;

Graph reduce(Graph graph) {

    /* vertex iterator */
    using vertex_descriptor = boost::graph_traits<Graph>::vertex_descriptor;

    std::cout << "# of vertices: " << num_vertices(graph) << "\n";
    std::cout << "# of edges:    " << num_edges(graph)    << "\n";

    std::set<vertex_descriptor> to_remove;

    /* iterator throught the graph  */
    for (auto self : mir(vertices(graph)))
        std::cout << graph[self].name << (boost::empty(mir(out_edges(self, graph)))? " has no children " : " is the parent of ");

        for(auto edge : mir(out_edges(self, graph))) {
            auto weight    = boost::get(boost::edge_weight, graph, edge);
            auto mid_point = target(edge, graph);

            if (to_remove.count(mid_point)) // already elided

            if (weight > 0.3f) {
                std::set<vertex_descriptor> traversed;
                for (auto hop : mir(out_edges(mid_point, graph))) {
                    auto hop_target = target(hop, graph);

                    if (hop_target != self)
                        add_edge(self, hop_target, graph);
                    std::cout << "\n DEBUG: " << graph[self].name << "  " << graph[mid_point].name << "  " << graph[hop_target].name << " ";
                std::cout << "\n";

                clear_vertex(mid_point, graph);

            std::cout << graph[mid_point].name;

        std::cout << "\n\n";

    for(auto vd : to_remove)
        clear_vertex(vd, graph);
        remove_vertex(vd, graph);

    std::cout << "# of vertices: " << num_vertices(graph) << "\n";
    std::cout << "# of edges:    " << num_edges(graph)    << "\n";

    return graph;

void save(Graph const& g, const char* fname);

int main() {
    auto const g = make();

    auto const h = reduce(g);

    save(g, "before.dot");
    save(h, "after.dot");

#include <boost/graph/graphviz.hpp>
#include <boost/property_map/property_map.hpp>
#include <boost/property_map/function_property_map.hpp>
#include <boost/property_map/transform_value_property_map.hpp>
#include <boost/format.hpp>
#include <fstream>

void save(Graph const& g, const char* fname) {
    std::ofstream ofs(fname);
    using namespace boost;

            make_label_writer(make_function_property_map<Graph::vertex_descriptor, std::string>([&] (Graph::vertex_descriptor v){ return g[v].name; })),
            make_label_writer(make_transform_value_property_map([](float v){return boost::format("%1.1f") % v;}, boost::get(edge_weight, g)))
# of vertices: 7
# of edges:    6
Jeanie is the parent of 
 DEBUG: Jeanie  Debbie  Jeanie 
 DEBUG: Jeanie  Debbie  Amanda 

Debbie has no children 

Rick is the parent of Jeanie
 DEBUG: Rick  Margaret  Rick 

John is the parent of Jeanie
 DEBUG: John  Benjamin  John 

Amanda is the parent of Jeanie

Margaret has no children 

Benjamin has no children 

# of vertices: 4
# of edges:    3
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