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Location: LEMON/LEMON-official/test/gomory_hu_test.cc

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kpeter (Peter Kovacs)
Entirely rework CapacityScaling (#180) - Use the new interface similarly to NetworkSimplex. - Rework the implementation using an efficient internal structure for handling the residual network. This improvement made the code much faster (up to 2-5 times faster on large graphs). - Handle GEQ supply type (LEQ is not supported). - Handle negative costs for arcs of finite capacity. (Note that this algorithm cannot handle arcs of negative cost and infinite upper bound, thus it returns UNBOUNDED if such an arc exists.) - Extend the documentation.
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#include <iostream>



#include "test_tools.h"

#include <lemon/smart_graph.h>

#include <lemon/concepts/graph.h>

#include <lemon/concepts/maps.h>

#include <lemon/lgf_reader.h>

#include <lemon/gomory_hu.h>

#include <cstdlib>



using namespace std;

using namespace lemon;



typedef SmartGraph Graph;



char test_lgf[] =

  "@nodes\n"

  "label\n"

  "0\n"

  "1\n"

  "2\n"

  "3\n"

  "4\n"

  "@arcs\n"

  "     label capacity\n"

  "0 1  0     1\n"

  "1 2  1     1\n"

  "2 3  2     1\n"

  "0 3  4     5\n"

  "0 3  5     10\n"

  "0 3  6     7\n"

  "4 2  7     1\n"

  "@attributes\n"

  "source 0\n"

  "target 3\n";

  

void checkGomoryHuCompile()

{

  typedef int Value;

  typedef concepts::Graph Graph;



  typedef Graph::Node Node;

  typedef Graph::Edge Edge;

  typedef concepts::ReadMap<Edge, Value> CapMap;

  typedef concepts::ReadWriteMap<Node, bool> CutMap;



  Graph g;

  Node n;

  CapMap cap;

  CutMap cut;

  Value v;

  int d;



  GomoryHu<Graph, CapMap> gh_test(g, cap);

  const GomoryHu<Graph, CapMap>&

    const_gh_test = gh_test;



  gh_test.run();



  n = const_gh_test.predNode(n);

  v = const_gh_test.predValue(n);

  d = const_gh_test.rootDist(n);

  v = const_gh_test.minCutValue(n, n);

  v = const_gh_test.minCutMap(n, n, cut);

}



GRAPH_TYPEDEFS(Graph);

typedef Graph::EdgeMap<int> IntEdgeMap;

typedef Graph::NodeMap<bool> BoolNodeMap;



int cutValue(const Graph& graph, const BoolNodeMap& cut,

	     const IntEdgeMap& capacity) {



  int sum = 0;

  for (EdgeIt e(graph); e != INVALID; ++e) {

    Node s = graph.u(e);

    Node t = graph.v(e);



    if (cut[s] != cut[t]) {

      sum += capacity[e];

    }

  }

  return sum;

}





int main() {

  Graph graph;

  IntEdgeMap capacity(graph);



  std::istringstream input(test_lgf);

  GraphReader<Graph>(graph, input).

    edgeMap("capacity", capacity).run();



  GomoryHu<Graph> ght(graph, capacity);

  ght.run();



  for (NodeIt u(graph); u != INVALID; ++u) {

    for (NodeIt v(graph); v != u; ++v) {

      Preflow<Graph, IntEdgeMap> pf(graph, capacity, u, v);

      pf.runMinCut();

      BoolNodeMap cm(graph);

      ght.minCutMap(u, v, cm);

      check(pf.flowValue() == ght.minCutValue(u, v), "Wrong cut 1");

      check(cm[u] != cm[v], "Wrong cut 2");

      check(pf.flowValue() == cutValue(graph, cm, capacity), "Wrong cut 3");



      int sum=0;

      for(GomoryHu<Graph>::MinCutEdgeIt a(ght, u, v);a!=INVALID;++a)

        sum+=capacity[a]; 

      check(sum == ght.minCutValue(u, v), "Problem with MinCutEdgeIt");



      sum=0;

      for(GomoryHu<Graph>::MinCutNodeIt n(ght, u, v,true);n!=INVALID;++n)

        sum++;

      for(GomoryHu<Graph>::MinCutNodeIt n(ght, u, v,false);n!=INVALID;++n)

        sum++;

      check(sum == countNodes(graph), "Problem with MinCutNodeIt");

    }

  }

  

  return 0;

}