18 KiB
18 KiB
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Line data Source code 1 : // *************************************************************** 2 : // SPDX-FileCopyrightText: Copyright 2024 Ricardo Montañana Gómez 3 : // SPDX-FileType: SOURCE 4 : // SPDX-License-Identifier: MIT 5 : // *************************************************************** 6 : 7 : #include <sstream> 8 : #include <vector> 9 : #include <list> 10 : #include "Mst.h" 11 : /* 12 : Based on the code from https://www.softwaretestinghelp.com/minimum-spanning-tree-tutorial/ 13 : 14 : */ 15 : 16 : namespace bayesnet { 17 116 : Graph::Graph(int V) : V(V), parent(std::vector<int>(V)) 18 : { 19 434 : for (int i = 0; i < V; i++) 20 376 : parent[i] = i; 21 58 : G.clear(); 22 58 : T.clear(); 23 58 : } 24 1152 : void Graph::addEdge(int u, int v, float wt) 25 : { 26 1152 : G.push_back({ wt, { u, v } }); 27 1152 : } 28 5326 : int Graph::find_set(int i) 29 : { 30 : // If i is the parent of itself 31 5326 : if (i == parent[i]) 32 2304 : return i; 33 : else 34 : //else recursively find the parent of i 35 3022 : return find_set(parent[i]); 36 : } 37 318 : void Graph::union_set(int u, int v) 38 : { 39 318 : parent[u] = parent[v]; 40 318 : } 41 58 : void Graph::kruskal_algorithm() 42 : { 43 : // sort the edges ordered on decreasing weight 44 4484 : stable_sort(G.begin(), G.end(), [](const auto& left, const auto& right) {return left.first > right.first;}); 45 1210 : for (int i = 0; i < G.size(); i++) { 46 : int uSt, vEd; 47 1152 : uSt = find_set(G[i].second.first); 48 1152 : vEd = find_set(G[i].second.second); 49 1152 : if (uSt != vEd) { 50 318 : T.push_back(G[i]); // add to mst std::vector 51 318 : union_set(uSt, vEd); 52 : } 53 : } 54 58 : } 55 : 56 318 : void insertElement(std::list<int>& variables, int variable) 57 : { 58 318 : if (std::find(variables.begin(), variables.end(), variable) == variables.end()) { 59 318 : variables.push_front(variable); 60 : } 61 318 : } 62 : 63 58 : std::vector<std::pair<int, int>> reorder(std::vector<std::pair<float, std::pair<int, int>>> T, int root_original) 64 : { 65 : // Create the edges of a DAG from the MST 66 : // replacing unordered_set with list because unordered_set cannot guarantee the order of the elements inserted 67 58 : auto result = std::vector<std::pair<int, int>>(); 68 58 : auto visited = std::vector<int>(); 69 58 : auto nextVariables = std::list<int>(); 70 58 : nextVariables.push_front(root_original); 71 434 : while (nextVariables.size() > 0) { 72 376 : int root = nextVariables.front(); 73 376 : nextVariables.pop_front(); 74 1328 : for (int i = 0; i < T.size(); ++i) { 75 952 : auto [weight, edge] = T[i]; 76 952 : auto [from, to] = edge; 77 952 : if (from == root || to == root) { 78 318 : visited.insert(visited.begin(), i); 79 318 : if (from == root) { 80 212 : result.push_back({ from, to }); 81 212 : insertElement(nextVariables, to); 82 : } else { 83 106 : result.push_back({ to, from }); 84 106 : insertElement(nextVariables, from); 85 : } 86 : } 87 : } 88 : // Remove visited 89 694 : for (int i = 0; i < visited.size(); ++i) { 90 318 : T.erase(T.begin() + visited[i]); 91 : } 92 376 : visited.clear(); 93 : } 94 58 : if (T.size() > 0) { 95 0 : for (int i = 0; i < T.size(); ++i) { 96 0 : auto [weight, edge] = T[i]; 97 0 : auto [from, to] = edge; 98 0 : result.push_back({ from, to }); 99 : } 100 : } 101 116 : return result; 102 58 : } 103 : 104 58 : MST::MST(const std::vector<std::string>& features, const torch::Tensor& weights, const int root) : features(features), weights(weights), root(root) {} 105 58 : std::vector<std::pair<int, int>> MST::maximumSpanningTree() 106 : { 107 58 : auto num_features = features.size(); 108 58 : Graph g(num_features); 109 : // Make a complete graph 110 376 : for (int i = 0; i < num_features - 1; ++i) { 111 1470 : for (int j = i + 1; j < num_features; ++j) { 112 1152 : g.addEdge(i, j, weights[i][j].item<float>()); 113 : } 114 : } 115 58 : g.kruskal_algorithm(); 116 58 : auto mst = g.get_mst(); 117 116 : return reorder(mst, root); 118 58 : } 119 : 120 : } |
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| Generated by: LCOV version 2.0-1 |
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