// Ceres Solver - A fast non-linear least squares minimizer

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// http://ceres-solver.org/

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// Author: Sameer Agarwal (sameeragarwal@google.com)

#include "ceres/single_linkage_clustering.h"

#include "ceres/collections_port.h"

#include "ceres/graph.h"

#include "gtest/gtest.h"

namespace ceres {

namespace internal {

TEST(SingleLinkageClustering, GraphHasTwoComponents) {

  WeightedGraph<int> graph;

  const int kNumVertices = 6;

  for (int i = 0; i < kNumVertices; ++i) {

    graph.AddVertex(i);

  }

  // Graph structure:

  //

  //  0-1-2-3 4-5

  graph.AddEdge(0, 1, 1.0);

  graph.AddEdge(1, 2, 1.0);

  graph.AddEdge(2, 3, 1.0);

  graph.AddEdge(4, 5, 1.0);

  SingleLinkageClusteringOptions options;

  HashMap<int, int> membership;

  ComputeSingleLinkageClustering(options, graph, &membership);

  EXPECT_EQ(membership.size(), kNumVertices);

  EXPECT_EQ(membership[1], membership[0]);

  EXPECT_EQ(membership[2], membership[0]);

  EXPECT_EQ(membership[3], membership[0]);

  EXPECT_NE(membership[4], membership[0]);

  EXPECT_NE(membership[5], membership[0]);

  EXPECT_EQ(membership[4], membership[5]);

}

TEST(SingleLinkageClustering, ComponentWithWeakLink) {

  WeightedGraph<int> graph;

  const int kNumVertices = 6;

  for (int i = 0; i < kNumVertices; ++i) {

    graph.AddVertex(i);

  }

  // Graph structure:

  //

  //  0-1-2-3 4-5

  graph.AddEdge(0, 1, 1.0);

  graph.AddEdge(1, 2, 1.0);

  graph.AddEdge(2, 3, 1.0);

  // This component should break up into two.

  graph.AddEdge(4, 5, 0.5);

  SingleLinkageClusteringOptions options;

  HashMap<int, int> membership;

  ComputeSingleLinkageClustering(options, graph, &membership);

  EXPECT_EQ(membership.size(), kNumVertices);

  EXPECT_EQ(membership[1], membership[0]);

  EXPECT_EQ(membership[2], membership[0]);

  EXPECT_EQ(membership[3], membership[0]);

  EXPECT_NE(membership[4], membership[0]);

  EXPECT_NE(membership[5], membership[0]);

  EXPECT_NE(membership[4], membership[5]);

}

TEST(SingleLinkageClustering, ComponentWithWeakLinkAndStrongLink) {

  WeightedGraph<int> graph;

  const int kNumVertices = 6;

  for (int i = 0; i < kNumVertices; ++i) {

    graph.AddVertex(i);

  }

  // Graph structure:

  //

  //  0-1-2-3 4-5

  graph.AddEdge(0, 1, 1.0);

  graph.AddEdge(1, 2, 1.0);

  graph.AddEdge(2, 3, 0.5);  // Weak link

  graph.AddEdge(0, 3, 1.0);

  // This component should break up into two.

  graph.AddEdge(4, 5, 1.0);

  SingleLinkageClusteringOptions options;

  HashMap<int, int> membership;

  ComputeSingleLinkageClustering(options, graph, &membership);

  EXPECT_EQ(membership.size(), kNumVertices);

  EXPECT_EQ(membership[1], membership[0]);

  EXPECT_EQ(membership[2], membership[0]);

  EXPECT_EQ(membership[3], membership[0]);

  EXPECT_EQ(membership[4], membership[5]);

}

}  // namespace internal

}  // namespace ceres