如何在提升图中访问边缘信息?

How to access edge information in Boost Graph?

本文关键字：访问 边缘 信息      更新时间：2023-10-16

主要问题：

我能够创建一个图形实现，其中包含分配给顶点和边的信息结构：

struct vertex_info {std::string name;};
struct edge_info {std::string name;};
typedef boost::adjacency_list<
boost::vecS,
boost::vecS,
boost::undirectedS,
vertex_info,
edge_info> UndirectedGraph;

对于UndirectedGraph、g的实例，我可以轻松地迭代顶点，并访问它们的信息：

for(size_t i=0; i<boost::num_vertices(g); i++){
std::cout << g[i].name << std::endl;
}

但我无法弄清楚如何对边缘做同样的事情。我遇到了一些迭代器来遍历所有边缘，但我无法将这些边缘作为某种对象或具有属性的东西访问。如何访问g的边缘信息？

一个最小的工作演示：

#include <iostream>
#include <utility>
#include <vector>
#include <string>
#include "boost/graph/graph_traits.hpp"
#include "boost/graph/adjacency_list.hpp"
int main(int argc, char *argv[])
{
//Add vertex information struct
struct vertex_info {
std::string name;
};
//Add edge information struct
struct edge_info {
std::string name;
};
//Typedef my graph implimentation
typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, vertex_info, edge_info> UndirectedGraph;
//Our set of edges, and count N: (0-7) and 8
enum {C, D, G, I, S, J, L, H, N};
const char *name = "CDGISJLH";
//Create a vector of edges
typedef std::pair<int, int> Edge;
std::vector<Edge> edgeVec;
edgeVec.push_back(Edge(C,D));
edgeVec.push_back(Edge(D,G));
edgeVec.push_back(Edge(I,G));
edgeVec.push_back(Edge(G,L));
edgeVec.push_back(Edge(H,G));
edgeVec.push_back(Edge(I,S));
edgeVec.push_back(Edge(S,J));
edgeVec.push_back(Edge(L,J));
edgeVec.push_back(Edge(H,J));
//Now we can initialize our graph using iterators from our above vector
UndirectedGraph g(edgeVec.begin(), edgeVec.end(), N);
std::cout << num_edges(g) << "n";  //Outputs: 9
//loop over vertices, access "name" property
for(size_t i=0; i<boost::num_vertices(g); i++){
//And add information to the edges
g[i].name = "foo";
}
//We can access the first vertice and print the property
std::cout << g[0].name << std::endl; //Outputs: foo
//Edge iterator for or graph
typedef boost::graph_traits<UndirectedGraph>::edge_iterator edge_iterator;
//Iterate through all the edges
std::pair<edge_iterator, edge_iterator> ei = boost::edges(g);
for(edge_iterator edge_iter = ei.first; edge_iter != ei.second; ++edge_iter) {
//How can I access the edge property???
}
}

我通过这个例子找出了问题所在：https://www.boost.org/doc/libs/1_71_0/libs/graph/doc/bundles.html

修复：

虽然我仍然不完全明白这一切是如何工作的。似乎您必须使用edge_iter作为g的某种索引：

//Edge iterator for or graph
typedef boost::graph_traits<MRFGraph>::edge_iterator edge_iterator;
//Iterate through all the edges
std::pair<edge_iterator, edge_iterator> ei = boost::edges(g);
for(edge_iterator edge_iter = ei.first; edge_iter != ei.second; ++edge_iter) {
g[*edge_iter].name = "bar";
std::cout << *edge_iter << ": " << g[*edge_iter].name << std::endl;
}

输出：

如果我将其添加到最小的工作演示中，它会产生以下输出：

9
foo
(0,1): bar
(1,2): bar
(3,2): bar
(2,6): bar
(7,2): bar
(3,4): bar
(4,5): bar
(6,5): bar
(7,5): bar

可能不是你想要的，但确实实现了你所追求的

#include <iostream>
#include <utility>
#include <vector>
#include <string>
#include <boost/graph/graph_traits.hpp>
#include <boost/graph/adjacency_list.hpp>
namespace boost {
enum edge_myname_t { edge_myname };
BOOST_INSTALL_PROPERTY(boost::edge, myname);
}
int main(int argc, char* argv[]) {
// Add vertex information struct
struct vertex_info {
std::string name;
};
// Add edge information struct
//struct edge_info {
//std::string name;
//};
using EdgeName = boost::property<boost::edge_myname_t, std::string>;
// Typedef my graph implimentation
using UndirectedGraph =
boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS,
vertex_info, EdgeName>;
// Our set of edges, and count N: (0-7) and 8
enum { C, D, G, I, S, J, L, H, N };
const char* name = "CDGISJLH";
// Create a vector of edges
//using Edge = std::pair<int, int>;
//std::vector<Edge> edgeVec;
//edgeVec.push_back(Edge(C, D));
//edgeVec.push_back(Edge(D, G));
//edgeVec.push_back(Edge(I, G));
//edgeVec.push_back(Edge(G, L));
//edgeVec.push_back(Edge(H, G));
//edgeVec.push_back(Edge(I, S));
//edgeVec.push_back(Edge(S, J));
//edgeVec.push_back(Edge(L, J));
//edgeVec.push_back(Edge(H, J));
// Now we can initialize our graph using iterators from our above vector
UndirectedGraph g(N);
//UndirectedGraph g(edgeVec.begin(), edgeVec.end(), N);
boost::add_edge(C, D, EdgeName("#1"), g);
boost::add_edge(D, G, EdgeName("#2"), g);
boost::add_edge(I, G, EdgeName("#3"), g);
boost::add_edge(G, L, EdgeName("#4"), g);
boost::add_edge(H, G, EdgeName("#5"), g);
boost::add_edge(I, S, EdgeName("#6"), g);
boost::add_edge(S, J, EdgeName("#7"), g);
boost::add_edge(L, J, EdgeName("#8"), g);
boost::add_edge(H, J, EdgeName("#9"), g);
boost::property_map<UndirectedGraph, boost::edge_myname_t>::type get_name =
boost::get(boost::edge_myname, g);
std::cout << num_edges(g) << "n";  // Outputs: 9
// loop over vertices, access "name" property
for (size_t i = 0; i < boost::num_vertices(g); i++) {
// And add information to the edges
g[i].name = "foo";
}
// We can access the first vertice and print the property
std::cout << g[0].name << std::endl;  // Outputs: foo
// Edge iterator for or graph
using EdgeIterator = boost::graph_traits<UndirectedGraph>::edge_iterator;
// Iterate through all the edges
std::pair<EdgeIterator, EdgeIterator> ei = boost::edges(g);
for (EdgeIterator edge_iter = ei.first; edge_iter != ei.second; ++edge_iter) {
// How can I access the edge property???
std::cout << get_name[*edge_iter] << "n";
}
}

我只是针对自己的可读性问题稍微修改了一些代码。

有关参考，请查看此内容。

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