1 // Ceres Solver - A fast non-linear least squares minimizer 2 // Copyright 2013 Google Inc. All rights reserved. 3 // http://code.google.com/p/ceres-solver/ 4 // 5 // Redistribution and use in source and binary forms, with or without 6 // modification, are permitted provided that the following conditions are met: 7 // 8 // * Redistributions of source code must retain the above copyright notice, 9 // this list of conditions and the following disclaimer. 10 // * Redistributions in binary form must reproduce the above copyright notice, 11 // this list of conditions and the following disclaimer in the documentation 12 // and/or other materials provided with the distribution. 13 // * Neither the name of Google Inc. nor the names of its contributors may be 14 // used to endorse or promote products derived from this software without 15 // specific prior written permission. 16 // 17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 18 // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 21 // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 22 // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 23 // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24 // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 25 // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 26 // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 27 // POSSIBILITY OF SUCH DAMAGE. 28 // 29 // Author: sameeragarwal (at) google.com (Sameer Agarwal) 30 31 // This include must come before any #ifndef check on Ceres compile options. 32 #include "ceres/internal/port.h" 33 34 #ifndef CERES_NO_SUITESPARSE 35 36 #include "ceres/single_linkage_clustering.h" 37 38 #include "ceres/graph.h" 39 #include "ceres/collections_port.h" 40 #include "ceres/graph_algorithms.h" 41 42 namespace ceres { 43 namespace internal { 44 45 int ComputeSingleLinkageClustering( 46 const SingleLinkageClusteringOptions& options, 47 const Graph<int>& graph, 48 HashMap<int, int>* membership) { 49 CHECK_NOTNULL(membership)->clear(); 50 51 // Initially each vertex is in its own cluster. 52 const HashSet<int>& vertices = graph.vertices(); 53 for (HashSet<int>::const_iterator it = vertices.begin(); 54 it != vertices.end(); 55 ++it) { 56 (*membership)[*it] = *it; 57 } 58 59 for (HashSet<int>::const_iterator it1 = vertices.begin(); 60 it1 != vertices.end(); 61 ++it1) { 62 const int vertex1 = *it1; 63 const HashSet<int>& neighbors = graph.Neighbors(vertex1); 64 for (HashSet<int>::const_iterator it2 = neighbors.begin(); 65 it2 != neighbors.end(); 66 ++it2) { 67 const int vertex2 = *it2; 68 69 // Since the graph is undirected, only pay attention to one side 70 // of the edge and ignore weak edges. 71 if ((vertex1 > vertex2) || 72 (graph.EdgeWeight(vertex1, vertex2) < options.min_similarity)) { 73 continue; 74 } 75 76 // Use a union-find algorithm to keep track of the clusters. 77 const int c1 = FindConnectedComponent(vertex1, membership); 78 const int c2 = FindConnectedComponent(vertex2, membership); 79 80 if (c1 == c2) { 81 continue; 82 } 83 84 if (c1 < c2) { 85 (*membership)[c2] = c1; 86 } else { 87 (*membership)[c1] = c2; 88 } 89 } 90 } 91 92 // Make sure that every vertex is connected directly to the vertex 93 // identifying the cluster. 94 int num_clusters = 0; 95 for (HashMap<int, int>::iterator it = membership->begin(); 96 it != membership->end(); 97 ++it) { 98 it->second = FindConnectedComponent(it->first, membership); 99 if (it->first == it->second) { 100 ++num_clusters; 101 } 102 } 103 104 return num_clusters; 105 } 106 107 } // namespace internal 108 } // namespace ceres 109 110 #endif // CERES_NO_SUITESPARSE 111
