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Diffstat (limited to 'internal/ceres/single_linkage_clustering.cc')
-rw-r--r-- | internal/ceres/single_linkage_clustering.cc | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/internal/ceres/single_linkage_clustering.cc b/internal/ceres/single_linkage_clustering.cc new file mode 100644 index 0000000..0a8b20c --- /dev/null +++ b/internal/ceres/single_linkage_clustering.cc @@ -0,0 +1,110 @@ +// Ceres Solver - A fast non-linear least squares minimizer +// Copyright 2013 Google Inc. All rights reserved. +// http://code.google.com/p/ceres-solver/ +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are met: +// +// * Redistributions of source code must retain the above copyright notice, +// this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above copyright notice, +// this list of conditions and the following disclaimer in the documentation +// and/or other materials provided with the distribution. +// * Neither the name of Google Inc. nor the names of its contributors may be +// used to endorse or promote products derived from this software without +// specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" +// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE +// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR +// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF +// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS +// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN +// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) +// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +// POSSIBILITY OF SUCH DAMAGE. +// +// Author: sameeragarwal@google.com (Sameer Agarwal) + +// This include must come before any #ifndef check on Ceres compile options. +#include "ceres/internal/port.h" + +#ifndef CERES_NO_SUITESPARSE + +#include "ceres/single_linkage_clustering.h" + +#include "ceres/graph.h" +#include "ceres/collections_port.h" +#include "ceres/graph_algorithms.h" + +namespace ceres { +namespace internal { + +int ComputeSingleLinkageClustering( + const SingleLinkageClusteringOptions& options, + const Graph<int>& graph, + HashMap<int, int>* membership) { + CHECK_NOTNULL(membership)->clear(); + + // Initially each vertex is in its own cluster. + const HashSet<int>& vertices = graph.vertices(); + for (HashSet<int>::const_iterator it = vertices.begin(); + it != vertices.end(); + ++it) { + (*membership)[*it] = *it; + } + + for (HashSet<int>::const_iterator it1 = vertices.begin(); + it1 != vertices.end(); + ++it1) { + const int vertex1 = *it1; + const HashSet<int>& neighbors = graph.Neighbors(vertex1); + for (HashSet<int>::const_iterator it2 = neighbors.begin(); + it2 != neighbors.end(); + ++it2) { + const int vertex2 = *it2; + + // Since the graph is undirected, only pay attention to one side + // of the edge and ignore weak edges. + if ((vertex1 > vertex2) || + (graph.EdgeWeight(vertex1, vertex2) < options.min_similarity)) { + continue; + } + + // Use a union-find algorithm to keep track of the clusters. + const int c1 = FindConnectedComponent(vertex1, membership); + const int c2 = FindConnectedComponent(vertex2, membership); + + if (c1 == c2) { + continue; + } + + if (c1 < c2) { + (*membership)[c2] = c1; + } else { + (*membership)[c1] = c2; + } + } + } + + // Make sure that every vertex is connected directly to the vertex + // identifying the cluster. + int num_clusters = 0; + for (HashMap<int, int>::iterator it = membership->begin(); + it != membership->end(); + ++it) { + it->second = FindConnectedComponent(it->first, membership); + if (it->first == it->second) { + ++num_clusters; + } + } + + return num_clusters; +} + +} // namespace internal +} // namespace ceres + +#endif // CERES_NO_SUITESPARSE |