Boost圖庫 - 找不到adjacent_vertices函數

Question

我正在嘗試編寫一個算法（貪婪地）找到圖的色數。 為此，我需要能夠查詢給定頂點的相鄰頂點。 我的功能如下：

int Network::greedy_colouring() {
    // create an undirected graph with the vertices and edges of the first one
    UndirectedGraph g;
    copy_graph(network, g);

    int vertices_amount = num_vertices(g);
    // Assign the first color to first vertex
    std::map<std::string, int> vertex_colouring;
    vertex_pair_iterators vp = vertices(g);
    vertex_colouring[g[*vp.first].name] = 0;

    ++vp.first; // start from second vertex
    for (; vp.first != vp.second; ++vp.first)
        vertex_colouring[g[*vp.first].name] = -1;
    // A temporary array to store the available colors. True
    // value of available[cr] would mean that the color cr is
    // assigned to one of its adjacent vertices
    bool available[vertices_amount];
    for (int cr = 0; cr < vertices_amount; cr++)
        available[cr] = false;

    // Assign colors to remaining V-1 vertices
    vp = vertices(g); // reset to beginning
    ++vp.first; // start from second vertex
    for (; vp.first != vp.second; ++vp.first) {
        // Process all adjacent vertices and flag their colors
        // as unavailable
        for (std::pair<adjacency_it, adjacency_it> neighbours = boost::adjacent_vertices(g[*vp.first], g);
            neighbours.first != neighbours.second; ++neighbours.first)
            if (vertex_colouring[g[*neighbours.first].name] != -1)
                available[vertex_colouring[g[*neighbours.first].name]] = true;

        // Find the first available color
        int cr;
        for (cr = 0; cr < vertices_amount; cr++)
            if (available[cr] == false)
                break;

        vertex_colouring[g[*vp.first].name] = cr; // Assign the found color

        // Reset the values back to false for the next iteration
        neighbours = boost::adjacent_vertices(g[*vp.first], g); // reset to beginning

        for (; neighbours.first != neighbours.second; ++neighbours.first)
            if (vertex_colouring[g[*neighbours.first].name] != -1)
                available[vertex_colouring[g[*neighbours.first].name]] = false;
    }

    // print the result and find colour number
    unsigned colour_number = 0;
    for (std::map<std::string, int>::iterator it = vertex_colouring.begin(); it != vertex_colouring.end(); ++it) {
        std::cout << "Vertex " << it->first << " --->  Color " << it->second << std::endl;
        if (it->second > colour_number)
            colour_number = it->second;
    }
    return colour_number;
}

我得到的錯誤與調用：

std::pair<adjacency_it, adjacency_it> neighbours = boost::adjacent_vertices(g[*vp.first],g)

這給出了以下編譯錯誤：“錯誤：沒有匹配函數來調用'boost :: adjacency_iterator ...”（部分副本）。 注釋掉與函數adjacency相關的代碼可以編譯，所以我確信這是問題代碼。 函數中使用的一些typedef：

typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::bidirectionalS, Vertex, Edge > Graph;
typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, Vertex, Edge > UndirectedGraph; 

typedef std::pair<Vertex ,Vertex > vert_p;
typedef boost::graph_traits<Graph>::vertex_descriptor vertex_t;
typedef std::pair<boost::graph_traits<Graph>::edge_descriptor, bool> edge_t;
typedef boost::graph_traits<Graph>::in_edge_iterator in_edge_it;
typedef boost::graph_traits<Graph>::vertex_iterator vertex_iter;
typedef boost::graph_traits<Graph>::edge_iterator edge_iter;
typedef boost::property_map<Graph, boost::vertex_index_t>::type IndexMap;
typedef std::pair<vertex_iter, vertex_iter> vertex_pair_iterators;
typedef std::pair<in_edge_it, in_edge_it> edge_pair_iterators;
typedef boost::graph_traits<Graph>::adjacency_iterator adjacency_it;

任何人都可以告訴我我做錯了什么？

Answer 1

兩個問題：

1. 第一個參數需要是頂點描述符，而不是屬性包。 更改

    boost::adjacent_vertices(g[*vp.first], g) 

   成

    boost::adjacent_vertices(*vp.first, g) 

2. 返回類型是std::pair<adjacency_iterator, adjacency_iterator> 。 但是，您將adjacency_iterator定義為

    typedef boost::graph_traits<Graph>::adjacency_iterator adjacency_it; 

   什么時候需要

    typedef boost::graph_traits<UndirectedGraph>::adjacency_iterator adjacency_it; 

附加說明：

• 使用單獨的迭代器而不是vp.first和vp.second更容易（使用boost::tie來同時分配兩者）

• 您的比較中有一個“有毒”的無符號值，請將其明確寫為

   if(it->second > static_cast<int>(colour_number)) 

  或者在地圖中查看可能的-1值的邏輯。

• 保持由Vertex::name索引的顏色映射（這是一個字符串）可能效率很低。 您應該考慮使用vertex_descriptor索引。

  現在，由於您的頂點模型使用vecS作為VertexContainer，您實際上可以使用此描述符是[0, num_vertices(g))范圍內的整數索引這一事實。

  因此，您可以使用vector<int> （其中頂點描述符是矢量索引）替換map <>（具有錯誤的內存局部性）。

  如果要支持其他圖形模型，可以讓調用者傳入將頂點描述符映射到類似連續索引的IndexMap 。 BGL中的許多算法都使用這種方法。

• 顯然， bool[]可能（應該）是std::bitset甚至是std::vector<bool> 。 Boost有dynamic_bitset ，這可能是最好的。

  （我需要更好地理解你的算法。也許一組“采取”的顏色會更好。並且實現為一個未分類的連續速度集合，除非你預期顏色的數量要足夠大以至於有序/ hash lookup會更快（？！）。

---

始終使您的代碼自包含：

住在Coliru

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/copy.hpp>
#include <iostream>

struct Vertex {
    std::string name;
};

struct Edge {
};

typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::bidirectionalS, Vertex, Edge > Graph;
typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, Vertex, Edge > UndirectedGraph; 

Graph network;

int greedy_colouring() {
    using namespace boost;
    typedef boost::graph_traits<UndirectedGraph>::vertex_descriptor  vertex_descriptor;
    static_assert(is_integral<vertex_descriptor>::value, "IndexMap not provided yet TODO");

    typedef boost::graph_traits<UndirectedGraph>::vertex_iterator    vertex_iter;
    typedef boost::graph_traits<UndirectedGraph>::adjacency_iterator adjacency_it;

    // create an undirected graph with the vertices and edges of the first one
    UndirectedGraph g;
    copy_graph(network, g);

    vertex_iter vit, vend;
    tie(vit, vend) = vertices(g);

    size_t const vertices_amount = num_vertices(g);
    std::vector<int> vertex_colouring(vertices_amount, -1);
    vertex_colouring[*vit] = 0; // Assign the first color to first vertex

    // A temporary array to store the available colors. 
    // - available[cr]:  assigned to one of its adjacent vertices
    std::vector<bool> available(vertices_amount, false);

    for (++vit; vit!=vend; ++vit)
    {
        // Process all adjacent vertices and flag their colors as unavailable
        adjacency_it neighbour, neighbour_end;
        for (tie(neighbour, neighbour_end) = adjacent_vertices(*vit, g); neighbour != neighbour_end; ++neighbour)
            if (vertex_colouring[*neighbour] != -1)
                available[vertex_colouring[*neighbour]] = true;

        // Find the first available color
        vertex_colouring[*vit] = distance(available.begin(), std::find(available.begin(), available.end(), false));

        // Reset the values back to false for the next iteration
        for (tie(neighbour, neighbour_end) = adjacent_vertices(*vit, g); neighbour != neighbour_end; ++neighbour)
            if (vertex_colouring[*neighbour] != -1)
                available[vertex_colouring[*neighbour]] = false;
    }

    // print the result and find colour number
    for (vertex_descriptor v = 0; v < vertices_amount; ++v)
        std::cout << "Vertex " << v << " --->  Color " << vertex_colouring[v] << std::endl;

    return *std::max_element(vertex_colouring.begin(), vertex_colouring.end());
}

int main() { }