AENC/switchchain Changeset - f8cbbd135cc1 · Centrum Wiskunde & Informatica (CWI)

Changeset - f8cbbd135cc1

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Tom Bannink - 9 years ago 2017-02-02 18:30:09
tombannink@gmail.com

Add triangle counting

4 files changed with 30 insertions and 5 deletions:

cpp/exports.hpp

cpp/graph.hpp

cpp/showgraphs.m

cpp/switchchain.cpp

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cpp/exports.hpp

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 #pragma once
 #include <iostream>
 #include "graph.hpp"
 std::ostream &operator<<(std::ostream &s, const Edge &e) {
     s << '{' << e.u << ',' << e.v << '}';
     return s;
+}
 // Mathematica style export
 std::ostream &operator<<(std::ostream &s, const Graph &g) {
     if (g.edgeCount() == 0) {
         s << '{' << '}';
         return s;
+    }
     s << '{' << g.getEdge(0).u << '<' << '-' << '>' << g.getEdge(0).v;
     for (unsigned int i = 1; i < g.edgeCount(); ++i) {
         const Edge &e = g.getEdge(i);
         s << ',' << e.u << '<' << '-' << '>' << e.v;
+    }
     s << '}';
     return s;
+}

cpp/graph.hpp

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 #pragma once
 #include <cassert>
 #include <numeric>
 #include <vector>
 class Edge {
   public:
     unsigned int u, v;
     bool operator==(const Edge &e) const { return u == e.u && v == e.v; }
 };
 class DiDegree {
   public:
     unsigned int in;
     unsigned int out;
 };
 typedef std::vector<unsigned int> DegreeSequence;
 typedef std::vector<DiDegree> DiDegreeSequence;
 class Graph {
   public:
     Graph() {}
     Graph(unsigned int n) { adj.resize(n); }
     ~Graph() {}
     void resize(unsigned int n) {
         if (n < adj.size()) {
             edges.clear();
+        }
         adj.resize(n);
+    }
     unsigned int edgeCount() const { return edges.size(); }
     Edge &getEdge(unsigned int i) { return edges[i]; }
     const Edge &getEdge(unsigned int i) const { return edges[i]; }
     bool createFromDegreeSequence(const DegreeSequence &d) {
         // Havel-Hakimi algorithm
         unsigned int n = d.size();
         // degree, vertex index
         std::vector<std::pair<unsigned int, unsigned int>> degrees(n);
         for (unsigned int i = 0; i < n; ++i) {
             degrees[i].first = d[i];
             degrees[i].second = i;
+        }
         edges.clear();
         adj.resize(n);
         while (!degrees.empty()) {
             std::sort(degrees.begin(), degrees.end());
             // Highest degree is at back of the vector
             // Take it out
             unsigned int degree = degrees.back().first;
             unsigned int u = degrees.back().second;
             degrees.pop_back();
             if (degree > degrees.size()) {
                 edges.clear();
                 adj.clear();
                 return false;
+            }
             // Now loop over the last 'degree' entries of degrees
             auto rit = degrees.rbegin();
             for (unsigned int i = 0; i < degree; ++i) {
                 if (rit->first == 0 || !addEdge({u, rit->second})) {
                     edges.clear();
                     adj.clear();
                     return false;
+                }
                 rit->first--;
                 ++rit;
+            }
+        }
         return true;
+    }
     DegreeSequence getDegreeSequence() const {
         DegreeSequence d(adj.size());
         std::transform(adj.begin(), adj.end(), d.begin(),
                        [](const auto &u) { return u.size(); });
         return d;
@@ @@ -133,55 +133,70 @@ class Graph { @@
                 break;
+        }
         for (i2 = 0; i2 < adj[e2.u].size(); ++i2) {
             if (adj[e2.u][i2] == e2.v)
                 break;
+        }
         for (j2 = 0; j2 < adj[e2.v].size(); ++j2) {
             if (adj[e2.v][j2] == e2.u)
                 break;
+        }
         // Remove the old edges
         bool removedOne = false;
         for (auto iter = edges.begin(); iter != edges.end();) {
             if (*iter == e1) {
                 iter = edges.erase(iter);
                 if (removedOne)
                     break;
                 removedOne = true;
             } else if (*iter == e2) {
                 iter = edges.erase(iter);
                 if (removedOne)
                     break;
                 removedOne = true;
             } else {
                 ++iter;
+            }
+        }
         // Add the new edges
         if (switchType) {
             adj[e1.u][i1] = e2.u;
             adj[e1.v][j1] = e2.v;
             adj[e2.u][i2] = e1.u;
             adj[e2.v][j2] = e1.v;
             edges.push_back({e1.u, e2.u});
             edges.push_back({e1.v, e2.v});
         } else {
             adj[e1.u][i1] = e2.v;
             adj[e1.v][j1] = e2.u;
             adj[e2.u][i2] = e1.v;
             adj[e2.v][j2] = e1.u;
             edges.push_back({e1.u, e2.v});
             edges.push_back({e1.v, e2.u});
+        }
         return true;
+    }
     int countTriangles() const {
         int triangles = 0;
         for (auto& v : adj) {
             for (unsigned int i = 0; i < v.size(); ++i) {
                 for (unsigned int j = i + 1; j < v.size(); ++j) {
                     if (hasEdge({v[i], v[j]})) {
                         ++triangles;
+                    }
+                }
+            }
+        }
         assert(triangles % 3 == 0);
         return triangles / 3;
+    }
   private:
     // Graph is saved in two formats for speed
     // The two should be kept consistent at all times
     std::vector<std::vector<unsigned int>> adj;
     std::vector<Edge> edges;
 };

cpp/showgraphs.m

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 (* ::Package:: *)
 gsraw=Import[NotebookDirectory[]<>"graphdata.m"];
 gs=Map[Graph[#,GraphLayout->"CircularEmbedding"]&,gsraw];
 gs2=Map[Graph[#,GraphLayout->Automatic]&,gsraw];
 ListPlot[gsraw[[2]],Joined->True,PlotRange->All,AxesLabel->{"Step","Triangles"}]
 gs=Map[Graph[#,GraphLayout->"CircularEmbedding"]&,gsraw[[1]]];
 gs2=Map[Graph[#,GraphLayout->Automatic]&,gsraw[[1]]];
 Grid[Partition[gs,10],Frame->All]

cpp/switchchain.cpp

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@@ @@ -59,66 +59,72 @@ class SwitchChain { @@
             return false;
         return g.exchangeEdges(e1, e2, perm == 1);
+    }
     Graph g;
     std::mt19937 mt;
     std::uniform_int_distribution<> edgeDistribution;
     std::uniform_int_distribution<> permutationDistribution;
 };
 int main() {
     Graph g;
     // Generate a random degree sequence
     std::mt19937 gen(std::random_device{}());
     // 50 nodes with average degree 12
     DegreeSequence ds(50);
     std::poisson_distribution<> degDist(7);
     // Try at most 10 times to generate a valid sequence
     bool validGraph = false;
     for (int i = 0; i < 10; ++i) {
         std::generate(ds.begin(), ds.end(),
                       [&degDist, &gen] { return degDist(gen); });
         if (g.createFromDegreeSequence(ds)) {
             validGraph = true;
             break;
+        }
+    }
     if (!validGraph) {
         std::cerr << "Could not create graph from degree sequence.\n";
         return 1;
+    }
     std::sort(ds.begin(), ds.end());
     std::cout << "Degree sequence:";
     for (auto i : ds)
         std::cout << ' ' << i;
     std::cout << std::endl;
     SwitchChain chain;
     if (!chain.initialize(g)) {
         std::cerr << "Could not initialize Markov chain.\n";
         return 1;
+    }
     std::ofstream outfile("graphdata.m");
     outfile << '{';
     outfile << '{' << g;
     std::cout << "Starting switch Markov chain" << std::endl;
     int movesDone = 0;
     int movesTotal = 100000;
     constexpr int movesTotal = 10000;
     int triangles[movesTotal];
     for (int i = 0; i < movesTotal; ++i) {
         if (chain.doMove())
             ++movesDone;
         triangles[i] = chain.g.countTriangles();
         if (i % (movesTotal / 50) == (movesTotal / 50 - 1))
             outfile << ',' << chain.g;
+    }
     outfile << '}';
     outfile << '}' << ',' << '{' << triangles[0];
     for (int i = 1; i < movesTotal; ++i)
         outfile << ',' << triangles[i];
     outfile << '}' << '}';
     std::cout << movesDone << '/' << movesTotal << " moves succeeded."
               << std::endl;
     return 0;
+}

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