AENC/switchchain Changeset - a79267af1717 · Centrum Wiskunde & Informatica (CWI)

Changeset - a79267af1717

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Tom Bannink - 9 years ago 2017-01-27 16:09:48
tom.bannink@cwi.nl

Add Havel-Hakimi algorithm and mathematica output

2 files changed with 113 insertions and 44 deletions:

cpp/showgraphs.m

cpp/switchchain.cpp

104

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cpp/showgraphs.m

➞

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@@ new file 100644 @@
 (* ::Package:: *)
 gsraw=Import[NotebookDirectory[]<>"graphdata.m"];
 gs=Graph/@gsraw;
 Grid[Partition[gs,10],Frame->All]

cpp/switchchain.cpp

➞

Show inline comments

 #include <algorithm>
 #include <fstream>
 #include <iostream>
 #include <numeric>
 #include <random>
@@ @@ -6,7 +7,7 @@ @@
 class Edge {
   public:
     int u, v;
+    unsigned int u, v;
     bool operator==(const Edge &e) const { return u == e.u && v == e.v; }
 };
@@ @@ -24,30 +25,72 @@ std::ostream &operator<<(std::ostream &s, const Edge &e) { @@
 class DiDegree {
   public:
     int in;
     int out;
     unsigned int in;
     unsigned int out;
 };
 typedef std::vector<int> DegreeSequence;
+typedef std::vector<unsigned int> DegreeSequence;
 typedef std::vector<DiDegree> DiDegreeSequence;
 class Graph {
   public:
     Graph() {}
     Graph(int n) { adj.resize(n); }
+    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) {
         //
         // TODO
         //
         // See
         // http://stackoverflow.com/questions/13102738/creating-graphs-using-a-degree-sequence
         // See https://en.wikipedia.org/wiki/Havel%E2%80%93Hakimi_algorithm
         (void)d;
         return false;
         // 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 {
@@ @@ -57,8 +100,9 @@ class Graph { @@
         return d;
+    }
     // Assumes valid vertex indices
     bool hasEdge(const Edge &e) const {
         for (int v : adj[e.u]) {
+        for (unsigned int v : adj[e.u]) {
             if (v == e.v)
                 return true;
+        }
@@ @@ -66,6 +110,8 @@ class Graph { @@
+    }
     bool addEdge(const Edge &e) {
         if (e.u >= adj.size() || e.v >= adj.size())
             return false;
         if (hasEdge(e))
             return false;
         edges.push_back(e);
@@ @@ -91,20 +137,20 @@ class Graph { @@
+        }
         // Find the edges in the adjacency lists
         int i1, j1, i2, j2;
         for (i1 = 0; i1 < (int)adj[e1.u].size(); ++i1) {
         unsigned int i1, j1, i2, j2;
         for (i1 = 0; i1 < adj[e1.u].size(); ++i1) {
             if (adj[e1.u][i1] == e1.v)
                 break;
+        }
-        for (j1 = 0; j1 < (int)adj[e1.v].size(); ++j1) {
         for (j1 = 0; j1 < adj[e1.v].size(); ++j1) {
             if (adj[e1.v][j1] == e1.u)
                 break;
+        }
-        for (i2 = 0; i2 < (int)adj[e2.u].size(); ++i2) {
         for (i2 = 0; i2 < adj[e2.u].size(); ++i2) {
             if (adj[e2.u][i2] == e2.v)
                 break;
+        }
-        for (j2 = 0; j2 < (int)adj[e2.v].size(); ++j2) {
         for (j2 = 0; j2 < adj[e2.v].size(); ++j2) {
             if (adj[e2.v][j2] == e2.u)
                 break;
+        }
@@ @@ -146,12 +192,28 @@ class Graph { @@
         return true;
+    }
   private:
     // Graph is saved in two formats for speed
     // The two should be kept consistent at all times
     std::vector<std::vector<int>> adj;
+    std::vector<std::vector<unsigned int>> adj;
     std::vector<Edge> edges;
 };
 // 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;
+}
 class SwitchChain {
   public:
     SwitchChain() : mt(std::random_device{}()), permutationDistribution(0, 2) {
@@ @@ -161,31 +223,23 @@ class SwitchChain { @@
+    }
     ~SwitchChain() {}
     bool initialize(const DegreeSequence &d) {
         if (!g.createFromDegreeSequence(d))
             return false;
         edgeDistribution.param(
             std::uniform_int_distribution<>::param_type(0, g.edges.size() - 1));
         return true;
+    }
     bool initialize(const Graph &gstart) {
-        if (gstart.edges.size() == 0)
+        if (gstart.edgeCount() == 0)
             return false;
         g = gstart;
         edgeDistribution.param(
-            std::uniform_int_distribution<>::param_type(0, g.edges.size() - 1));
+            std::uniform_int_distribution<>::param_type(0, g.edgeCount() - 1));
         return true;
+    }
     bool doMove() {
         Edge e1 = g.edges[edgeDistribution(mt)];
         Edge e2 = g.edges[edgeDistribution(mt)];
         Edge e1 = g.getEdge(edgeDistribution(mt));
         Edge e2 = g.getEdge(edgeDistribution(mt));
         // Keep regenerating while conflicting edges
         int timeout = 0;
         while (edgeConflicts(e1, e2)) {
             e1 = g.edges[edgeDistribution(mt)];
             e2 = g.edges[edgeDistribution(mt)];
             e1 = g.getEdge(edgeDistribution(mt));
             e2 = g.getEdge(edgeDistribution(mt));
             ++timeout;
             if (timeout % 100 == 0) {
                 std::cerr << "Warning: sampled " << timeout
@@ @@ -214,13 +268,11 @@ class SwitchChain { @@
 };
 int main() {
     Graph g(6);
     g.addEdge({0, 1});
     g.addEdge({0, 2});
     g.addEdge({0, 3});
     g.addEdge({2, 3});
     g.addEdge({3, 4});
     g.addEdge({3, 5});
     Graph g;
     if (!g.createFromDegreeSequence({1, 2, 2, 2, 3, 3, 3})) {
         std::cerr << "Could not create graph from degree sequence.\n";
         return 1;
+    }
     SwitchChain chain;
     if (!chain.initialize(g)) {
@@ @@ -228,14 +280,22 @@ int main() { @@
         return 1;
+    }
     std::ofstream outfile("graphdata.m");
     outfile << '{' << g;
     std::cout << "Starting switch Markov chain" << std::endl;
     int movesDone = 0;
     int movesTotal = 10000;
     for (int i = 0; i < movesTotal; ++i)
     int movesTotal = 100000;
     for (int i = 0; i < movesTotal; ++i) {
         if (chain.doMove())
             ++movesDone;
         if (i % (movesTotal / 100) == (movesTotal / 100 - 1))
             outfile << ',' << chain.g;
+    }
     outfile << '}';
     std::cout << movesDone << '/' << movesTotal << " moves succeeded." << std::endl;
     std::cout << movesDone << '/' << movesTotal << " moves succeeded."
               << std::endl;
     return 0;
+}

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