Added bottom_up_cluster()

dlib/clustering.h

@@ -6,6 +6,7 @@
 #include "clustering/modularity_clustering.h"
 #include "clustering/chinese_whispers.h"
 #include "clustering/spectral_cluster.h"
+#include "clustering/bottom_up_cluster.h"
 #include "svm/kkmeans.h"
 
 #endif // DLIB_CLuSTERING_

dlib/clustering/bottom_up_cluster.h

+// Copyright (C) 2015  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_BOTTOM_uP_CLUSTER_Hh_
+#define DLIB_BOTTOM_uP_CLUSTER_Hh_
+
+#include <queue>
+#include <map>
+
+#include "bottom_up_cluster_abstract.h"
+#include "../algs.h"
+#include "../matrix.h"
+#include "../disjoint_subsets.h"
+#include "../graph_utils.h"
+
+
+namespace dlib
+{
+
+// ----------------------------------------------------------------------------------------
+
+    namespace buc_impl
+    {
+        inline void merge_sets (
+            matrix<double>& dists,
+            unsigned long dest,
+            unsigned long src
+        )
+        {
+            for (long r = 0; r < dists.nr(); ++r)
+                dists(dest,r) = dists(r,dest) = std::max(dists(r,dest), dists(r,src));
+        }
+
+        struct compare_dist
+        {
+            bool operator() (
+                const sample_pair& a,
+                const sample_pair& b
+            ) const
+            {
+                return a.distance() > b.distance();
+            }
+        };
+    }
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename EXP
+        >
+    unsigned long bottom_up_cluster (
+        const matrix_exp<EXP>& dists_,
+        std::vector<unsigned long>& labels,
+        unsigned long min_num_clusters,
+        double max_dist = std::numeric_limits<double>::infinity()
+    )
+    {
+        matrix<double> dists = matrix_cast<double>(dists_);
+        // make sure requires clause is not broken
+        DLIB_CASSERT(dists.nr() == dists.nc() && min_num_clusters > 0, 
+            "\t unsigned long bottom_up_cluster()"
+            << "\n\t Invalid inputs were given to this function."
+            << "\n\t dists.nr(): " << dists.nr() 
+            << "\n\t dists.nc(): " << dists.nc() 
+            << "\n\t min_num_clusters: " << min_num_clusters 
+            );
+
+        using namespace buc_impl;
+
+        labels.resize(dists.nr());
+        disjoint_subsets sets;
+        sets.set_size(dists.nr());
+        if (labels.size() == 0)
+            return 0;
+
+        // push all the edges in the graph into a priority queue so the best edges to merge
+        // come first.
+        std::priority_queue<sample_pair, std::vector<sample_pair>, compare_dist> que;
+        for (long r = 0; r < dists.nr(); ++r)
+            for (long c = r+1; c < dists.nc(); ++c)
+                que.push(sample_pair(r,c,dists(r,c)));
+
+        // Now start merging nodes.
+        for (unsigned long iter = min_num_clusters; iter < sets.size(); ++iter)
+        {
+            // find the next best thing to merge.
+            double best_dist = que.top().distance();
+            unsigned long a = sets.find_set(que.top().index1());
+            unsigned long b = sets.find_set(que.top().index2());
+            que.pop();
+            // we have been merging and modifying the distances, so make sure this distance
+            // is still valid and these guys haven't been merged already.
+            while(a == b || best_dist < dists(a,b))
+            {
+                // Haven't merged it yet, so put it back in with updated distance for
+                // reconsideration later.
+                if (a != b)
+                    que.push(sample_pair(a, b, dists(a, b)));
+
+                best_dist = que.top().distance();
+                a = sets.find_set(que.top().index1());
+                b = sets.find_set(que.top().index2());
+                que.pop();
+            }
+
+
+            // now merge these sets if the best distance is small enough
+            if (best_dist > max_dist)
+                break;
+            unsigned long news = sets.merge_sets(a,b);
+            unsigned long olds = (news==a)?b:a;
+            merge_sets(dists, news, olds);
+        }
+
+        // figure out which cluster each element is in.  Also make sure the labels are
+        // contiguous.
+        std::map<unsigned long, unsigned long> relabel;
+        for (unsigned long r = 0; r < labels.size(); ++r)
+        {
+            unsigned long l = sets.find_set(r);
+            // relabel to make contiguous
+            if (relabel.count(l) == 0)
+            {
+                unsigned long next = relabel.size();
+                relabel[l] = next;
+            }
+            labels[r] = relabel[l];
+        }
+
+
+        return relabel.size();
+    }
+
+// ----------------------------------------------------------------------------------------
+
+}
+
+#endif // DLIB_BOTTOM_uP_CLUSTER_Hh_
+

dlib/clustering/bottom_up_cluster_abstract.h

+// Copyright (C) 2015  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#undef DLIB_BOTTOM_uP_CLUSTER_ABSTRACT_Hh_
+#ifdef DLIB_BOTTOM_uP_CLUSTER_ABSTRACT_Hh_
+
+#include "../matrix.h"
+
+namespace dlib
+{
+
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename EXP
+        >
+    unsigned long bottom_up_cluster (
+        const matrix_exp<EXP>& dists,
+        std::vector<unsigned long>& labels,
+        unsigned long min_num_clusters,
+        double max_dist = std::numeric_limits<double>::infinity()
+    );
+    /*!
+        requires
+            - dists.nr() == dists.nc()
+            - min_num_clusters > 0
+            - dists == trans(dists)
+              (l.e. dists should be symmetric)
+        ensures
+            - Runs a bottom up agglomerative clustering algorithm.   
+            - Interprets dists as a matrix that gives the distances between dists.nr()
+              items.  In particular, we take dists(i,j) to be the distance between the ith
+              and jth element of some set.  This function clusters the elements of this set
+              into at least min_num_clusters (or dists.nr() if there aren't enough
+              elements).  Additionally, within each cluster, the maximum pairwise distance
+              between any two cluster elements is <= max_dist.
+            - returns the number of clusters found.
+            - #labels.size() == dists.nr()
+            - for all valid i:
+                - #labels[i] == the cluster ID of the node with index i (i.e. the node
+                  corresponding to the distances dists(i,*)).  
+                - 0 <= #labels[i] < the number of clusters found
+                  (i.e. cluster IDs are assigned contiguously and start at 0) 
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+}
+
+#endif // DLIB_BOTTOM_uP_CLUSTER_ABSTRACT_Hh_
+
+

dlib/test/clustering.cpp

@@ -220,6 +220,89 @@ namespace
         }
     }
 
+    void test_bottom_up_clustering()
+    {
+        std::vector<dpoint> pts;
+        pts.push_back(dpoint(0.0,0.0));
+        pts.push_back(dpoint(0.5,0.0));
+        pts.push_back(dpoint(0.5,0.5));
+        pts.push_back(dpoint(0.0,0.5));
+
+        pts.push_back(dpoint(3.0,3.0));
+        pts.push_back(dpoint(3.5,3.0));
+        pts.push_back(dpoint(3.5,3.5));
+        pts.push_back(dpoint(3.0,3.5));
+
+        pts.push_back(dpoint(7.0,7.0));
+        pts.push_back(dpoint(7.5,7.0));
+        pts.push_back(dpoint(7.5,7.5));
+        pts.push_back(dpoint(7.0,7.5));
+
+        matrix<double> dists(pts.size(), pts.size());
+        for (long r = 0; r < dists.nr(); ++r)
+            for (long c = 0; c < dists.nc(); ++c)
+                dists(r,c) = length(pts[r]-pts[c]);
+
+
+        matrix<unsigned long,0,1> truth(12);
+        truth = 0, 0, 0, 0,
+                1, 1, 1, 1,
+                2, 2, 2, 2;
+
+        std::vector<unsigned long> labels;
+        DLIB_TEST(bottom_up_cluster(dists, labels, 3) == 3);
+        DLIB_TEST(mat(labels) == truth);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 1, 4.0) == 3);
+        DLIB_TEST(mat(labels) == truth);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 1, 4.95) == 2);
+        truth = 0, 0, 0, 0,
+                0, 0, 0, 0,
+                1, 1, 1, 1;
+        DLIB_TEST(mat(labels) == truth);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 1) == 1);
+        truth = 0, 0, 0, 0,
+                0, 0, 0, 0,
+                0, 0, 0, 0;
+        DLIB_TEST(mat(labels) == truth);
+
+        dists.set_size(0,0);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 3) == 0);
+        DLIB_TEST(labels.size() == 0);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 1) == 0);
+        DLIB_TEST(labels.size() == 0);
+
+        dists.set_size(1,1);
+        dists = 1;
+        DLIB_TEST(bottom_up_cluster(dists, labels, 3) == 1);
+        DLIB_TEST(labels.size() == 1);
+        DLIB_TEST(labels[0] == 0);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 1) == 1);
+        DLIB_TEST(labels.size() == 1);
+        DLIB_TEST(labels[0] == 0);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 1, 0) == 1);
+        DLIB_TEST(labels.size() == 1);
+        DLIB_TEST(labels[0] == 0);
+
+        dists.set_size(2,2);
+        dists = 1;
+        DLIB_TEST(bottom_up_cluster(dists, labels, 3) == 2);
+        DLIB_TEST(labels.size() == 2);
+        DLIB_TEST(labels[0] == 0);
+        DLIB_TEST(labels[1] == 1);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 1) == 1);
+        DLIB_TEST(labels.size() == 2);
+        DLIB_TEST(labels[0] == 0);
+        DLIB_TEST(labels[1] == 0);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 1, 1) == 1);
+        DLIB_TEST(labels.size() == 2);
+        DLIB_TEST(labels[0] == 0);
+        DLIB_TEST(labels[1] == 0);
+        DLIB_TEST(bottom_up_cluster(dists, labels, 1, 0.999) == 2);
+        DLIB_TEST(labels.size() == 2);
+        DLIB_TEST(labels[0] == 0);
+        DLIB_TEST(labels[1] == 1);
+    }
+
     class test_clustering : public tester
     {
     public:
@@ -232,6 +315,8 @@ namespace
         void perform_test (
         )
         {
+            test_bottom_up_clustering();
+
             dlib::rand rnd;
 
             std::vector<sample_pair> edges;