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Merge pull request #26 from levinkov/master
fixing bugs in complete graph fixing bugs in the Kernighan-Lin Algorithm. adding algorithm to solve an LP relaxation of the minimum cost multicut problem.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,179 @@ | ||
| #pragma once | ||
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| #include <cstddef> | ||
| #include <iterator> | ||
| #include <vector> | ||
| #include <algorithm> | ||
| #include <stack> | ||
| #include <unordered_map> | ||
| #include <unordered_set> | ||
| #include <queue> | ||
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| #include "andres/partition.hxx" | ||
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| namespace andres { | ||
| namespace graph { | ||
| namespace multicut { | ||
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| /// Greedy agglomerative decomposition of a graph. | ||
| /// | ||
| template<typename GRAPH, typename EVA, typename ELA> | ||
| void greedyFixation( | ||
| const GRAPH& graph, | ||
| EVA const& edge_values, | ||
| ELA& edge_labels | ||
| ) | ||
| { | ||
| class DynamicGraph | ||
| { | ||
| public: | ||
| DynamicGraph(size_t n) : | ||
| vertices_(n), cut_edges_(n) | ||
| {} | ||
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| bool edgeExists(size_t a, size_t b) const | ||
| { | ||
| return !vertices_[a].empty() && vertices_[a].find(b) != vertices_[a].end(); | ||
| } | ||
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| std::unordered_map<size_t, typename EVA::value_type> const& getAdjacentVertices(size_t v) const | ||
| { | ||
| return vertices_[v]; | ||
| } | ||
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| typename EVA::value_type getEdgeWeight(size_t a, size_t b) const | ||
| { | ||
| return vertices_[a].at(b); | ||
| } | ||
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| bool isCutEdge(size_t a, size_t b) const | ||
| { | ||
| return !cut_edges_[a].empty() && cut_edges_[a].find(b) != cut_edges_[a].end(); | ||
| } | ||
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| void markEdgeCut(size_t a, size_t b) | ||
| { | ||
| cut_edges_[a].insert(b); | ||
| cut_edges_[b].insert(a); | ||
| } | ||
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| void removeVertex(size_t v) | ||
| { | ||
| for (auto& p : vertices_[v]) | ||
| { | ||
| vertices_[p.first].erase(v); | ||
| cut_edges_[p.first].erase(v); | ||
| } | ||
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| vertices_[v].clear(); | ||
| cut_edges_[v].clear(); | ||
| } | ||
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| void setEdgeWeight(size_t a, size_t b, typename EVA::value_type w) | ||
| { | ||
| vertices_[a][b] = w; | ||
| vertices_[b][a] = w; | ||
| } | ||
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| private: | ||
| std::vector<std::unordered_set<size_t>> cut_edges_; | ||
| std::vector<std::unordered_map<size_t, typename EVA::value_type>> vertices_; | ||
| }; | ||
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| struct Edge | ||
| { | ||
| Edge(size_t _a, size_t _b, typename EVA::value_type _w) | ||
| { | ||
| if (_a > _b) | ||
| std::swap(_a, _b); | ||
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| a = _a; | ||
| b = _b; | ||
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| w = _w; | ||
| } | ||
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| size_t a; | ||
| size_t b; | ||
| size_t edition; | ||
| typename EVA::value_type w; | ||
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| bool operator <(Edge const& other) const | ||
| { | ||
| return fabs(w) < fabs(other.w); | ||
| } | ||
| }; | ||
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| std::vector<std::unordered_map<size_t, size_t>> edge_editions(graph.numberOfVertices()); | ||
| (graph.numberOfVertices()); | ||
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| DynamicGraph original_graph_cp(graph.numberOfVertices()); | ||
| std::priority_queue<Edge> Q; | ||
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| for (size_t i = 0; i < graph.numberOfEdges(); ++i) | ||
| { | ||
| auto a = graph.vertexOfEdge(i, 0); | ||
| auto b = graph.vertexOfEdge(i, 1); | ||
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| original_graph_cp.setEdgeWeight(a, b, edge_values[i]); | ||
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| auto e = Edge(a, b, edge_values[i]); | ||
| e.edition = ++edge_editions[e.a][e.b]; | ||
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| Q.push(e); | ||
| } | ||
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| andres::Partition<size_t> partition(graph.numberOfVertices()); | ||
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| while (!Q.empty()) | ||
| { | ||
| auto edge = Q.top(); | ||
| Q.pop(); | ||
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| if (!original_graph_cp.edgeExists(edge.a, edge.b) || edge.edition < edge_editions[edge.a][edge.b]) | ||
| continue; | ||
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| if (edge.w > typename EVA::value_type() && !original_graph_cp.isCutEdge(edge.a, edge.b)) | ||
| { | ||
| auto stable_vertex = edge.a; | ||
| auto merge_vertex = edge.b; | ||
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| if (original_graph_cp.getAdjacentVertices(stable_vertex).size() < original_graph_cp.getAdjacentVertices(merge_vertex).size()) | ||
| std::swap(stable_vertex, merge_vertex); | ||
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| partition.merge(stable_vertex, merge_vertex); | ||
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| for (auto& p : original_graph_cp.getAdjacentVertices(merge_vertex)) | ||
| { | ||
| if (p.first == stable_vertex) | ||
| continue; | ||
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| typename EVA::value_type t = typename EVA::value_type(); | ||
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| if (original_graph_cp.edgeExists(stable_vertex, p.first)) | ||
| t = original_graph_cp.getEdgeWeight(stable_vertex, p.first); | ||
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| if (original_graph_cp.isCutEdge(merge_vertex, p.first)) | ||
| original_graph_cp.markEdgeCut(stable_vertex, p.first); | ||
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| original_graph_cp.setEdgeWeight(stable_vertex, p.first, p.second + t); | ||
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| auto e = Edge(stable_vertex, p.first, p.second + t); | ||
| e.edition = ++edge_editions[e.a][e.b]; | ||
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| Q.push(e); | ||
| } | ||
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| original_graph_cp.removeVertex(merge_vertex); | ||
| } | ||
| else if (edge.w < typename EVA::value_type()) | ||
| original_graph_cp.markEdgeCut(edge.a, edge.b); | ||
| } | ||
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| for (size_t i = 0; i < graph.numberOfEdges(); ++i) | ||
| edge_labels[i] = partition.find(graph.vertexOfEdge(i, 0)) == partition.find(graph.vertexOfEdge(i, 1)) ? 0 : 1; | ||
| } | ||
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| } // namespace multicut | ||
| } // namespace graph | ||
| } // namespace andres |
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