read_graphviz() in Boost::Graph, pass to constructor

Question

I have used a python library to generate the following GraphViz .dot file.

http://pastebin.com/mL7ck9Zp

I want to now read it into C++'s Boost::Graph so I can use Boost::Graph's library algorithms on it.

However, I need to do some preprocessing. In particular, I want to create a bundled property with a string constructor and have read_graphviz() pass the string in the label field in the dot file into the string constructor.

How do I go about doing this?

Answer 1

First thing to realize is that Boost documentation samples almost always refer to/are generated from the actual samples: libs/graph/example/read_graphviz.cpp

Second thing to realize is that BGL is highly generic. Highly. And it achieves much of this genericity on the concepts of Boost Property Maps.

Finally, observe that parsing from "free-form" (at least dynamically/untyped text form) into some kind of generic MutableGraph model is pushing the limits.

This explains how you would have to read important parts of the documentation under the docs for property_map.

Anyhow, since indeed the sample seems a bit dated, allow me to demonstrate:

1. Include the implementation of the parser into one translation unit:

   #include <libs/graph/src/read_graphviz_new.cpp>
   

   This way BGL remains a header-only library.

2. Prefer bundled properties these days:

   struct Vertex {
       std::string name, label, shape;
   };
   
   struct Edge {
       std::string label;
       double weight; // perhaps you need this later as well, just an example
   };
   
   typedef property<graph_name_t, std::string> graph_p;
   typedef adjacency_list<vecS, vecS, directedS, Vertex, Edge, graph_p> graph_t;
   

   We will be filling label, shape, name for vertices and edges.

3. The dynamic property maps are where the magic happens:

   dynamic_properties dp/*(ignore_other_properties)*/;
   

   This class provides type-erased access to a variety of underlying property maps identified by (name, typeid(key_type)).

   This means you can register the bundled properties, and map them to the graphviz attribute names:

   int main() {
       // Construct an empty graph and prepare the dynamic_property_maps.
       graph_t graph(0);
   
       dynamic_properties dp(ignore_other_properties);
       dp.property("node_id", get(&Vertex::name,  graph));
       dp.property("label",   get(&Vertex::label, graph));
       dp.property("shape",   get(&Vertex::shape, graph));
       dp.property("label",   get(&Edge::label,   graph));
   

   That's really all there is to it. (Read up on the magic of Bundled Properties, found via the page for the adjacency_list template).

   Though we don't need it, let's throw the graph property in the mix too (as in the documentation sample):

       // Use ref_property_map to turn a graph property into a property map
       boost::ref_property_map<graph_t *, std::string> gname(get_property(graph, graph_name));
       dp.property("name",    gname);
   

4. Now all that's left is reading the graph.

   Well. Okay then. And let's write it back out too, but with a new graph name, then:

   std::ifstream dot("input.dot");
   
   if (read_graphviz(dot, graph, dp/*, "node_id"*/)) {
       std::cout << "Graph name: '" << get_property(graph, graph_name) << "'\n";
       get_property(graph, graph_name) = "Let's give it a name";
       write_graphviz_dp(std::cout, graph, dp/*, "node_id"*/);
   }
   

5. Don't forget to link to Boost Regex

Full Demo

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#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graphviz.hpp>
#include <boost/property_map/dynamic_property_map.hpp>
#include <libs/graph/src/read_graphviz_new.cpp>
#include <boost/graph/graph_utility.hpp>

using namespace boost;

struct Vertex {
    std::string name, label, shape;
};

struct Edge {
    std::string label;
    double weight; // perhaps you need this later as well, just an example
};

typedef property<graph_name_t, std::string> graph_p;
typedef adjacency_list<vecS, vecS, directedS, Vertex, Edge, graph_p> graph_t;

int main() {
    // Construct an empty graph and prepare the dynamic_property_maps.
    graph_t graph(0);

    dynamic_properties dp/*(ignore_other_properties)*/;
    dp.property("node_id", get(&Vertex::name,  graph));
    dp.property("label",   get(&Vertex::label, graph));
    dp.property("shape",   get(&Vertex::shape, graph));
    dp.property("label",   get(&Edge::label,   graph));

    // Use ref_property_map to turn a graph property into a property map
    boost::ref_property_map<graph_t *, std::string> gname(get_property(graph, graph_name));
    dp.property("name",    gname);

    std::ifstream dot("input.dot");

    if (read_graphviz(dot, graph, dp/*, "node_id"*/)) {
        std::cout << "Graph name: '" << get_property(graph, graph_name) << "'\n";
        get_property(graph, graph_name) = "Let's give it a name";
        write_graphviz_dp(std::cout, graph, dp/*, "node_id"*/);
    }
}

Prints (note the empty name before, and the updated graph name attribute, after):

Graph name: ''
digraph G {
name="Let's give it a name";
n0 [label="A9\n", shape=box];
n1 [label="- [0.48%,19.42%]", shape=ellipse];
n11 [label="+ [0%,0%]", shape=ellipse];
n12 [label="- [0%,0.75%]", shape=ellipse];
n13 [label="+ [0.03%,1.33%]", shape=ellipse];
n14 [label="- [0%,0.75%]", shape=ellipse];
n15 [label="+ [0%,0%]", shape=ellipse];
n16 [label="+ [0%,0%]", shape=ellipse];
n17 [label="A14\n", shape=box];
n18 [label="+ [0.03%,2.51%]", shape=ellipse];
n19 [label="A15\n", shape=box];
n2 [label="A15\n", shape=box];
n20 [label="A6\n", shape=box];
n21 [label="A2\n", shape=box];
n22 [label="- [0%,1.11%]", shape=ellipse];
n23 [label="+ [0%,1%]", shape=ellipse];
n25 [label="- [0%,2.18%]", shape=ellipse];
n26 [label="+ [0%,1.79%]", shape=ellipse];
n27 [label="- [0%,1%]", shape=ellipse];
n28 [label="- [0%,0%]", shape=ellipse];
n29 [label="- [0%,0%]", shape=ellipse];
n3 [label="A11\n", shape=box];
n30 [label="- [0%,0%]", shape=ellipse];
n31 [label="- [0%,0%]", shape=ellipse];
n32 [label="- [0%,1%]", shape=ellipse];
n33 [label="A13\n", shape=box];
n34 [label="+ [0%,1%]", shape=ellipse];
n35 [label="- [0%,0%]", shape=ellipse];
n36 [label="- [0.01%,1.21%]", shape=ellipse];
n38 [label="A12\n", shape=box];
n39 [label="- [0%,1%]", shape=ellipse];
n4 [label="A4\n", shape=box];
n40 [label="+ [0%,1.17%]", shape=ellipse];
n42 [label="- [0%,0%]", shape=ellipse];
n43 [label="A12\n", shape=box];
n44 [label="+ [0%,1.11%]", shape=ellipse];
n45 [label="- [0%,1%]", shape=ellipse];
n47 [label="- [0%,0%]", shape=ellipse];
n49 [label="+ [0%,1.17%]", shape=ellipse];
n5 [label="+ [0%,0%]", shape=ellipse];
n52 [label="+ [0%,0.75%]", shape=ellipse];
n54 [label="A13\n", shape=box];
n55 [label="A14\n", shape=box];
n56 [label="- [0.03%,2.5%]", shape=ellipse];
n57 [label="+ [0.01%,2.27%]", shape=ellipse];
n59 [label="- [0%,0%]", shape=ellipse];
n6 [label="A7\n", shape=box];
n60 [label="+ [0%,1%]", shape=ellipse];
n63 [label="A15\n", shape=box];
n64 [label="+ [0.05%,1.34%]", shape=ellipse];
n65 [label="A15\n", shape=box];
n66 [label="- [0%,1%]", shape=ellipse];
n67 [label="+ [0.02%,2.44%]", shape=ellipse];
n7 [label="A14\n", shape=box];
n71 [label="+ [0.21%,3.83%]", shape=ellipse];
n8 [label="+ [0%,1.57%]", shape=ellipse];
n9 [label="- [0.01%,1.22%]", shape=ellipse];
n0->n1  [label=f];
n0->n2  [label=t];
n17->n18  [label="<=110"];
n17->n19  [label=">110"];
n19->n20  [label="<=8"];
n19->n49  [label=">8"];
n2->n3  [label="<=228"];
n2->n71  [label=">228"];
n20->n21  [label=aa];
n20->n25  [label=c];
n20->n26  [label=cc];
n20->n27  [label=d];
n20->n28  [label=e];
n20->n29  [label=ff];
n20->n30  [label=i];
n20->n31  [label=j];
n20->n32  [label=k];
n20->n33  [label=m];
n20->n38  [label=q];
n20->n42  [label=r];
n20->n43  [label=w];
n20->n47  [label=x];
n21->n22  [label="<=41"];
n21->n23  [label=">41"];
n3->n4  [label="<=3"];
n3->n63  [label=">3"];
n33->n34  [label=g];
n33->n35  [label=p];
n33->n36  [label=s];
n38->n39  [label=f];
n38->n40  [label=t];
n4->n5  [label=l];
n4->n6  [label=u];
n4->n54  [label=y];
n43->n44  [label=f];
n43->n45  [label=t];
n54->n55  [label=g];
n54->n59  [label=p];
n54->n60  [label=s];
n55->n56  [label="<=204"];
n55->n57  [label=">204"];
n6->n7  [label=bb];
n6->n11  [label=dd];
n6->n12  [label=ff];
n6->n13  [label=h];
n6->n14  [label=j];
n6->n15  [label=n];
n6->n16  [label=o];
n6->n17  [label=v];
n6->n52  [label=z];
n63->n64  [label="<=4"];
n63->n65  [label=">4"];
n65->n66  [label="<=5"];
n65->n67  [label=">5"];
n7->n8  [label="<=164"];
n7->n9  [label=">164"];
}