我正在尝试对图形进行一些统计(比较2个图形)。但是在比较边缘时会有问题。

因此,我创建了两个带有一些边的图形,然后创建了一些用于顶点和边操作的模板。对于顶点,它工作得很好,但是对于边缘,则工作不正常。

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/reverse_graph.hpp>
#include <boost/graph/iteration_macros.hpp>
#include <boost/graph/graph_utility.hpp>
typedef boost::adjacency_list < boost::vecS, boost::vecS,
                            boost::undirectedS > Graph;

template <typename T> std::set<T> operator-(const std::set<T>& a,
                                            const std::set<T>& b)
{
    std::set<T> r;
    std::set_difference(
                        a.begin(), a.end(),
                        b.begin(), b.end(),
                        std::inserter(r, r.end()));

    return r;
}

template <typename T> std::set<T> operator/(const std::set<T>& a,
                                            const std::set<T>& b)
{
    std::set<T> r;
    std::set_intersection(
                          a.begin(), a.end(),
                          b.begin(), b.end(),
                          std::inserter(r, r.end()));

    return r;
}



void compare(const Graph& a, const Graph& b)
{
    std::set<Graph::vertex_descriptor > av, bv, samev, extrav, missingv;
    std::set<Graph::edge_descriptor> ae, be, re, samee, extrae, missinge;

    BGL_FORALL_VERTICES_T(v, a, Graph) av.insert(v);
    BGL_FORALL_VERTICES_T(v, b, Graph) bv.insert(v);
    samev    = (av / bv);
    extrav   = (bv - av);
    missingv = (av - bv);


    BGL_FORALL_EDGES_T(e, a, Graph) ae.insert(e);
    BGL_FORALL_EDGES_T(e, b, Graph) be.insert(e);

    samee    = (ae / be);
    extrae   = (be - ae);
    missinge = (ae - be);

    // TODO(silgon): reverse_graph
    // boost::reverse_graph<Graph> r(b);
    // BGL_FORALL_EDGES_T(e, r, Graph) re.insert(e);
    std::cout << "---- Vertices ----\n"
              << "same: " << samev.size() << std::endl
              << "extra: " << extrav.size() << std::endl
              << "missing: " << missingv.size() << std::endl;

    std::cout << "---- Edges ----\n"
              << "same: " << samee.size() << std::endl
              << "extra: " << extrae.size() << std::endl
              << "missing: " << missinge.size() << std::endl;
}

int main()
{
    Graph a;
    {
        boost::graph_traits<Graph>::vertex_descriptor v, u, y;
        u = boost::vertex(1, a);
        v = boost::vertex(2, a);
        y = boost::vertex(3, a);
        boost::add_edge(u, v, a);
    }
    Graph b;
    {
        boost::graph_traits<Graph>::vertex_descriptor v, u, y;
        u = vertex(1, b);
        v = vertex(2, b);
        y = vertex(3, b);
        boost::add_edge(u, v, b);
        boost::add_edge(y, v, b);
    }

    const char* name = "123456";
    std::cout << "---Graph1---" << "\n";
    boost::print_graph(a);
    std::cout << "Edges: ";
    boost::print_edges(a,name);
    std::cout << "---Graph2---" << "\n";
    boost::print_graph(b);
    std::cout << "Edges: ";
    boost::print_edges(b,name);

    compare(a,b);
}

至于程序的结果如下:
---Graph1---
0 <-->
1 <--> 2
2 <--> 1
Edges: (2,3)
---Graph2---
0 <-->
1 <--> 2
2 <--> 1 3
3 <--> 2
Edges: (2,3) (4,3)
---- Vertices ----
same: 3
extra: 1
missing: 0
---- Edges ----
same: 0
extra: 2
missing: 1

您可以看到边之一相同(2,3),但是在进行操作时并未考虑到边,因此在结果中将其说为same:0,并且多余或缺失的结果均不起作用。

最佳答案

深入研究Boost的edge_descriptor实现(在boost/graph/detail/edge.hpp中,我们发现每个边缘描述符都存储源vertex_descriptor和目标vertex_descriptor,还存储着edge属性的指针。该指针对于edge_descriptor s相同的两个边缘是不同的。

这意味着您需要定义自己的std::set比较器,用于set_intersectionset_difference / ojit_code操作,例如像这样:

struct edge_cmp
{
  bool operator () (const Graph::edge_descriptor& a, const Graph::edge_descriptor& b) const
  {
    if (a.m_source < b.m_source) { return true; }
    if (a.m_source > b.m_source) { return false; }
    return (a.m_target < b.m_target);
  }
};

这种类型的比较器对象必须传递给您构造的所有集合以及交集/差值调用。

I've forked your code on ideone并进行相应的修改。输出:
---- Vertices ----
same: 3
extra: 1
missing: 0
---- Edges ----
same: 1
extra: 1
missing: 0

关于c++ - Boost Graph边缘比较不起作用,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/34921262/

10-12 07:24
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