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// 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 WeightedGraph<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
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