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use prim algorithm instead of kruskal for finding MST, which yields the parent map.

release/4.3a0
Kai Ni 2010-01-07 06:25:54 +00:00
parent 20c6f29823
commit 6298a45050
3 changed files with 20 additions and 15 deletions
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24
cpp/FactorGraph-inl.h
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@ -20,7 +20,7 @@
#include <boost/format.hpp> #include <boost/format.hpp>
#include <boost/graph/graph_traits.hpp> #include <boost/graph/graph_traits.hpp>
#include <boost/graph/adjacency_list.hpp> #include <boost/graph/adjacency_list.hpp>
#include <boost/graph/kruskal_min_spanning_tree.hpp> #include <boost/graph/prim_minimum_spanning_tree.hpp>
#include <colamd/colamd.h> #include <colamd/colamd.h>
#include "Ordering.h" #include "Ordering.h"
#include "FactorGraph.h" #include "FactorGraph.h"
@ -276,13 +276,14 @@ void FactorGraph<Factor>::associateFactor(int index, sharedFactor factor) {
/* ************************************************************************* */ /* ************************************************************************* */
template<class Factor> template<class Factor>
vector<pair<string, string> > FactorGraph<Factor>::findMinimumSpanningTree() const { map<string, string> FactorGraph<Factor>::findMinimumSpanningTree() const {
typedef boost::adjacency_list< typedef boost::adjacency_list<
boost::vecS, boost::vecS, boost::undirectedS, boost::vecS, boost::vecS, boost::undirectedS,
boost::property<boost::vertex_name_t, string>, boost::property<boost::vertex_name_t, string>,
boost::property<boost::edge_weight_t, int> > Graph; boost::property<boost::edge_weight_t, int> > Graph;
typedef boost::graph_traits<Graph>::vertex_descriptor Vertex; typedef boost::graph_traits<Graph>::vertex_descriptor Vertex;
typedef boost::graph_traits<Graph>::vertex_iterator VertexIterator;
typedef boost::graph_traits<Graph>::edge_descriptor Edge; typedef boost::graph_traits<Graph>::edge_descriptor Edge;
// convert the factor graph to boost graph // convert the factor graph to boost graph
@ -316,16 +317,17 @@ vector<pair<string, string> > FactorGraph<Factor>::findMinimumSpanningTree() con
} }
// find minimum spanning tree // find minimum spanning tree
vector<Edge> spanning_tree; vector<Vertex> p_map(boost::num_vertices(g));
boost::kruskal_minimum_spanning_tree(g, back_inserter(spanning_tree)); prim_minimum_spanning_tree(g, &p_map[0]);
// convert edge to skin // convert edge to string pairs
vector<pair<string, string> > tree; map<string, string> tree;
for (vector<Edge>::iterator ei = spanning_tree.begin(); ei VertexIterator itVertex = boost::vertices(g).first;
!= spanning_tree.end(); ++ei) { for (vector<Vertex>::iterator vi = p_map.begin(); vi!=p_map.end(); itVertex++, vi++) {
string key1 = boost::get(boost::vertex_name, g, boost::source(*ei,g)); string key = boost::get(boost::vertex_name, g, *itVertex);
string key2 = boost::get(boost::vertex_name, g, boost::target(*ei,g)); string parent = boost::get(boost::vertex_name, g, *vi);
tree.push_back(make_pair(key1, key2)); // printf("%s parent: %s\n", key.c_str(), parent.c_str());
tree.insert(make_pair(key, parent));
} }
return tree; return tree;

4
cpp/FactorGraph.h
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@ -117,9 +117,9 @@ namespace gtsam {
std::vector<sharedFactor> findAndRemoveFactors(const std::string& key); std::vector<sharedFactor> findAndRemoveFactors(const std::string& key);
/** /**
* find the minimum spanning tree * find the minimum spanning tree.
*/ */
std::vector<std::pair<std::string, std::string> > findMinimumSpanningTree() const; std::map<std::string, std::string> findMinimumSpanningTree() const;
private: private:
/** Associate factor index with the variables connected to the factor */ /** Associate factor index with the variables connected to the factor */

7
cpp/testGaussianFactorGraph.cpp
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@ -743,8 +743,11 @@ TEST( GaussianFactorGraph, findMinimumSpanningTree )
g.add("x2", I, "x4", I, b, 0); g.add("x2", I, "x4", I, b, 0);
g.add("x3", I, "x4", I, b, 0); g.add("x3", I, "x4", I, b, 0);
vector<pair<string, string> > tree = g.findMinimumSpanningTree(); map<string, string> tree = g.findMinimumSpanningTree();
LONGS_EQUAL(3,tree.size()); CHECK(tree["x1"].compare("x1")==0);
CHECK(tree["x2"].compare("x1")==0);
CHECK(tree["x3"].compare("x1")==0);
CHECK(tree["x4"].compare("x1")==0);
} }
/* ************************************************************************* */ /* ************************************************************************* */