Computing a dominator graph using Boost's Lengauer Tarjan algorithm and display it using graphviz

Question

Let me first of all apologize in case I have violated the rules, as I am aware my question has already been asked in a modified way here: Lengauer Tarjan Algorithm in BGL (boost graph library). However, I am (still) unable to use the answer in order to display the result correctly.

To be more precise: I followed the answer linked and have sucessfully applied the Lengauer-Tarjan algorithm to my graph (which for convenience is part of the Boost documentation: http://www.boost.org/doc/libs/1_55_0/libs/graph/test/dominator_tree_test.cpp). Now, if understand the code correctly the relevant information about the dominator tree is stored in domTreePredMap which is of type PredMap:

const int numOfVertices = testSet[i].numOfVertices;
//See example for test_sets - it just the same routine
G g(
  testSet[i].edges.begin(), testSet[i].edges.end(),
  numOfVertices);

typedef graph_traits<G>::vertex_descriptor Vertex;
typedef property_map<G, vertex_index_t>::type IndexMap;
typedef
  iterator_property_map<vector<Vertex>::iterator, IndexMap>
  PredMap;

vector<Vertex> domTreePredVector, domTreePredVector2;
IndexMap indexMap(get(vertex_index, g));
graph_traits<G>::vertex_iterator uItr, uEnd;
int j = 0;
for (tie(uItr, uEnd) = vertices(g); uItr != uEnd; ++uItr, ++j)
{
  put(indexMap, *uItr, j);
}

// Lengauer-Tarjan dominator tree algorithm
domTreePredVector =
  vector<Vertex>(num_vertices(g), graph_traits<G>::null_vertex());
PredMap domTreePredMap =
  make_iterator_property_map(domTreePredVector.begin(), indexMap);

lengauer_tarjan_dominator_tree(g, vertex(0, g), domTreePredMap);`

For me one of the main advantages of Boost is the possibility to automatically generated graphical output using graphviz with write_graphviz(cout, g), where g is a graph from typedef G:

typedef adjacency_list<
    listS,
    listS,
    bidirectionalS,
    property<vertex_index_t, std::size_t>, no_property> G;

However, I am unable to translate the DomTreePredMap into something write_graphviz(cout, X) can understand. I appreciate any help outlining how a graph can be constructed from the domTreePredMap, which can be printed using graphviz.

Thank you all for reading all this and helping me out.

Answer 1

Sorry to bother you - I managed to find the answer myself in the boost documentary:

Here is an minimal working example to illustrate my problem. Basically I want to compute the graph (one the left) and its dominator tree (on the right) as illustrated here: http://www.boost.org/doc/libs/1_40_0/libs/graph/doc/lengauer_tarjan_dominator.htm#fig:dominator-tree-example and print both graphs using graphviz.

Following the example I have managed to compute and print the original graph and execute the Lengauer-Tarjan algorithms on it. The information on the dominator tree is stored in the DomPredMap and can be copied into an integer vector. At position i of the vector idom the id of the parent of node i is stored. If no parent node exists, max_int is stored. This information can be used to add the edges from idom[i] to i to the testSet from which the graph g2 can finally be constructed. Thank you for all your help and patience.

 #include <iostream>
 #include <boost/graph/graphviz.hpp>
 #include <boost/graph/adjacency_list.hpp>
 #include <boost/graph/dominator_tree.hpp>
 #include <algorithm>
 #include <fstream>
 #include <cstdlib>
 #include <string>
 #include <sstream>
 #include <vector> 
 using namespace std;


 struct DominatorCorrectnessTestSet
    {
      typedef pair<int, int> edge;

      int numOfVertices;
      vector<edge> edges;
      vector<int> correctIdoms;
    };

    using namespace boost;

    typedef adjacency_list<
        listS,
        listS,
        bidirectionalS,
        property<vertex_index_t, std::size_t>, no_property> G;

    int main(int, char*[])
    {



     typedef DominatorCorrectnessTestSet::edge edge;

      DominatorCorrectnessTestSet testSet[1];



      testSet[0].numOfVertices = 8, //Orignal problem see left hand side
      testSet[0].edges.push_back(edge(0, 1));
      testSet[0].edges.push_back(edge(1, 2));
      testSet[0].edges.push_back(edge(1, 3));
      testSet[0].edges.push_back(edge(2, 7));
      testSet[0].edges.push_back(edge(3, 4));
      testSet[0].edges.push_back(edge(4, 5));
      testSet[0].edges.push_back(edge(4, 6));
      testSet[0].edges.push_back(edge(5, 7));
      testSet[0].edges.push_back(edge(6, 4));

      testSet[1].numOfVertices = 8; //Used to create Dominator Tree

    const int numOfVertices = testSet[0].numOfVertices;

    G g(
      testSet[0].edges.begin(), testSet[0].edges.end(),
      numOfVertices);

    typedef graph_traits<G>::vertex_descriptor Vertex;
    typedef property_map<G, vertex_index_t>::type IndexMap;
    typedef
      iterator_property_map<vector<Vertex>::iterator, IndexMap>
      PredMap;

    vector<Vertex> domTreePredVector, domTreePredVector2;
    IndexMap indexMap(get(vertex_index, g));
    graph_traits<G>::vertex_iterator uItr, uEnd;
    int j = 0;
    for (tie(uItr, uEnd) = vertices(g); uItr != uEnd; ++uItr, ++j)
    {
      put(indexMap, *uItr, j);
    }
    write_graphviz(cout, g);
    // Lengauer-Tarjan dominator tree algorithm
    domTreePredVector =
      vector<Vertex>(num_vertices(g), graph_traits<G>::null_vertex());
    PredMap domTreePredMap =
      make_iterator_property_map(domTreePredVector.begin(), indexMap);

    lengauer_tarjan_dominator_tree(g, vertex(0, g), domTreePredMap);
vector<int> idom(num_vertices(g));
         for (tie(uItr, uEnd) = vertices(g); uItr != uEnd; ++uItr)
         {
           if (get(domTreePredMap, *uItr) != graph_traits<G>::null_vertex())
             idom[get(indexMap, *uItr)] =
               get(indexMap, get(domTreePredMap, *uItr));
           else
             idom[get(indexMap, *uItr)] = (numeric_limits<int>::max)();
         }

        for (int k =0; k <idom.size();k++){

             if (k>0){
             cout << idom[k] << " nach " << k << endl;
             int t= idom[k];
             testSet[1].edges.push_back(edge(t, k));
             }
         }

       G g2(testSet[1].edges.begin(), testSet[1].edges.end(),8);
       int jj=0;
       for (tie(uItr, uEnd) = vertices(g2); uItr != uEnd; ++uItr, ++jj)
           {
             put(indexMap, *uItr, jj);
           }

         write_graphviz(cout, g2);
         cout << endl;


return 0;

}