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

// Copyright 2015 Google Inc. All rights reserved.

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

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

#include "ceres/graph_algorithms.h"

#include <algorithm>

#include "gtest/gtest.h"

#include "ceres/collections_port.h"

#include "ceres/graph.h"

#include "ceres/internal/port.h"

#include "ceres/internal/scoped_ptr.h"

namespace ceres {

namespace internal {

using std::vector;

TEST(IndependentSetOrdering, Chain) {

  Graph<int> graph;

  graph.AddVertex(0);

  graph.AddVertex(1);

  graph.AddVertex(2);

  graph.AddVertex(3);

  graph.AddVertex(4);

  graph.AddEdge(0, 1);

  graph.AddEdge(1, 2);

  graph.AddEdge(2, 3);

  graph.AddEdge(3, 4);

  // 0-1-2-3-4

  // 0, 2, 4 should be in the independent set.

  vector<int> ordering;

  int independent_set_size = IndependentSetOrdering(graph, &ordering);

  sort(ordering.begin(), ordering.begin() + 3);

  sort(ordering.begin() + 3, ordering.end());

  EXPECT_EQ(independent_set_size, 3);

  EXPECT_EQ(ordering.size(), 5);

  EXPECT_EQ(ordering[0], 0);

  EXPECT_EQ(ordering[1], 2);

  EXPECT_EQ(ordering[2], 4);

  EXPECT_EQ(ordering[3], 1);

  EXPECT_EQ(ordering[4], 3);

}

TEST(IndependentSetOrdering, Star) {

  Graph<int> graph;

  graph.AddVertex(0);

  graph.AddVertex(1);

  graph.AddVertex(2);

  graph.AddVertex(3);

  graph.AddVertex(4);

  graph.AddEdge(0, 1);

  graph.AddEdge(0, 2);

  graph.AddEdge(0, 3);

  graph.AddEdge(0, 4);

  //      1

  //      |

  //    4-0-2

  //      |

  //      3

  // 1, 2, 3, 4 should be in the independent set.

  vector<int> ordering;

  int independent_set_size = IndependentSetOrdering(graph, &ordering);

  EXPECT_EQ(independent_set_size, 4);

  EXPECT_EQ(ordering.size(), 5);

  EXPECT_EQ(ordering[4], 0);

  sort(ordering.begin(), ordering.begin() + 4);

  EXPECT_EQ(ordering[0], 1);

  EXPECT_EQ(ordering[1], 2);

  EXPECT_EQ(ordering[2], 3);

  EXPECT_EQ(ordering[3], 4);

}

TEST(Degree2MaximumSpanningForest, PreserveWeights) {

  WeightedGraph<int> graph;

  graph.AddVertex(0, 1.0);

  graph.AddVertex(1, 2.0);

  graph.AddEdge(0, 1, 0.5);

  graph.AddEdge(1, 0, 0.5);

  scoped_ptr<WeightedGraph<int> > forest(Degree2MaximumSpanningForest(graph));

  const HashSet<int>& vertices = forest->vertices();

  EXPECT_EQ(vertices.size(), 2);

  EXPECT_EQ(forest->VertexWeight(0), 1.0);

  EXPECT_EQ(forest->VertexWeight(1), 2.0);

  EXPECT_EQ(forest->Neighbors(0).size(), 1.0);

  EXPECT_EQ(forest->EdgeWeight(0, 1), 0.5);

}

TEST(Degree2MaximumSpanningForest, StarGraph) {

  WeightedGraph<int> graph;

  graph.AddVertex(0);

  graph.AddVertex(1);

  graph.AddVertex(2);

  graph.AddVertex(3);

  graph.AddVertex(4);

  graph.AddEdge(0, 1, 1.0);

  graph.AddEdge(0, 2, 2.0);

  graph.AddEdge(0, 3, 3.0);

  graph.AddEdge(0, 4, 4.0);

  scoped_ptr<WeightedGraph<int> > forest(Degree2MaximumSpanningForest(graph));

  const HashSet<int>& vertices = forest->vertices();

  EXPECT_EQ(vertices.size(), 5);

  {

    const HashSet<int>& neighbors = forest->Neighbors(0);

    EXPECT_EQ(neighbors.size(), 2);

    EXPECT_TRUE(neighbors.find(4) != neighbors.end());

    EXPECT_TRUE(neighbors.find(3) != neighbors.end());

  }

  {

    const HashSet<int>& neighbors = forest->Neighbors(3);

    EXPECT_EQ(neighbors.size(), 1);

    EXPECT_TRUE(neighbors.find(0) != neighbors.end());

  }

  {

    const HashSet<int>& neighbors = forest->Neighbors(4);

    EXPECT_EQ(neighbors.size(), 1);

    EXPECT_TRUE(neighbors.find(0) != neighbors.end());

  }

  {

    const HashSet<int>& neighbors = forest->Neighbors(1);

    EXPECT_EQ(neighbors.size(), 0);

  }

  {

    const HashSet<int>& neighbors = forest->Neighbors(2);

    EXPECT_EQ(neighbors.size(), 0);

  }

}

TEST(VertexTotalOrdering, TotalOrdering) {

  Graph<int> graph;

  graph.AddVertex(0);

  graph.AddVertex(1);

  graph.AddVertex(2);

  graph.AddVertex(3);

  // 0-1

  //   |

  // 2-3

  // 0,1 and 2 have degree 1 and 3 has degree 2.

  graph.AddEdge(0, 1);

  graph.AddEdge(2, 3);

  VertexTotalOrdering<int> less_than(graph);

  for (int i = 0; i < 4; ++i) {

    EXPECT_FALSE(less_than(i, i)) << "Failing vertex: " << i;

    for (int j = 0; j < 4; ++j) {

      if (i != j) {

        EXPECT_TRUE(less_than(i, j) ^ less_than(j, i))

            << "Failing vertex pair: " << i << " " << j;

      }

    }

  }

  for (int i = 0; i < 3; ++i) {

    EXPECT_TRUE(less_than(i, 3));

    EXPECT_FALSE(less_than(3, i));

  }

}

TEST(StableIndependentSet, BreakTies) {

  Graph<int> graph;

  graph.AddVertex(0);

  graph.AddVertex(1);

  graph.AddVertex(2);

  graph.AddVertex(3);

  graph.AddEdge(0, 1);

  graph.AddEdge(0, 2);

  graph.AddEdge(0, 3);

  graph.AddEdge(1, 2);

  graph.AddEdge(1, 3);

  graph.AddEdge(2, 3);

  // Since this is a completely connected graph, the independent set

  // contains exactly one vertex. StableIndependentSetOrdering

  // guarantees that it will always be the first vertex in the

  // ordering vector.

  {

    vector<int> ordering;

    ordering.push_back(0);

    ordering.push_back(1);

    ordering.push_back(2);

    ordering.push_back(3);

    const int independent_set_size =

        StableIndependentSetOrdering(graph, &ordering);

    EXPECT_EQ(independent_set_size, 1);

    EXPECT_EQ(ordering[0], 0);

  }

  {

    vector<int> ordering;

    ordering.push_back(1);

    ordering.push_back(0);

    ordering.push_back(2);

    ordering.push_back(3);

    const int independent_set_size =

        StableIndependentSetOrdering(graph, &ordering);

    EXPECT_EQ(independent_set_size, 1);

    EXPECT_EQ(ordering[0], 1);

  }

}

}  // namespace internal

}  // namespace ceres