source: lemon-0.x/demo/descriptor_map_demo.cc @ 2391:14a343be7a5a

/* -*- C++ -*-
 *
 * This file is a part of LEMON, a generic C++ optimization library
 *
 * Copyright (C) 2003-2007
 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
 * (Egervary Research Group on Combinatorial Optimization, EGRES).
 *
 * Permission to use, modify and distribute this software is granted
 * provided that this copyright notice appears in all copies. For
 * precise terms see the accompanying LICENSE file.
 *
 * This software is provided "AS IS" with no warranty of any kind,
 * express or implied, and with no claim as to its suitability for any
 * purpose.
 *
 */

/// \ingroup demos
/// \file
/// \brief Using descriptor map and own special map types.
///
/// This demo shows how can be used the DescriptorMap class
/// which helps to use unique label for each node or edge.
/// And it gives an example how easy is creating own map types.
///
/// \include descriptor_map_demo.cc

#include <lemon/list_graph.h>
#include <lemon/graph_utils.h>
#include <lemon/graph_writer.h>
#include <lemon/dim2.h>
#include <lemon/graph_to_eps.h>

#include <lemon/random.h>

#include <iostream>

#include <cmath>


using namespace lemon;

// Special dim2::Point<double> map type 
//
// It gives back a position for each node. The position of the nodes
// are on the circle with the given center and radius.
//
// Because we use the descriptor map it will hold the proprty
// described above even if a node added or deleted.
template <typename Graph>
class CircleMap {
public:

  typedef dim2::Point<double> Value;
  typedef typename Graph::Node Key;

  CircleMap(const Graph& _graph, 
            const Value& _center = Value(0.0, 0.0), 
            double _radius = 1.0) 
    : descriptor(_graph), center(_center), radius(_radius) {}

  Value operator[](const Key& key) const {
    double angle = descriptor[key] * 2 * M_PI 
      / double(descriptor.inverse().size());
    double x = std::cos(angle) * radius + center.x;
    double y = std::sin(angle) * radius + center.y;
    return Value(x, y);
  }

private:
  
  DescriptorMap<Graph, typename Graph::Node> descriptor;
  Value center;
  double radius;
};

int main() {
  typedef ListGraph Graph;
  typedef Graph::Node Node;
  typedef Graph::Edge Edge;
  
  // Generating a graph

  std::cout << "Generating graph: " << std::endl;

  Graph graph;
  
  const int NODE = 16;
  for (int i = 0; i < NODE; ++i) {
    graph.addNode();
  } 

  // Creating descriptor map and inverse
  DescriptorMap<Graph, Node> nodeDesc(graph);
  DescriptorMap<Graph, Node>::InverseMap nodeInv(nodeDesc);

  // Adding edges
  // The descriptor map always maps an integer value for each node.
  // The range of the values is always [0..n - 1] where n is the
  // number of the nodes of the graph. The inverse map gives back the
  // the node by its descriptor value. 
  //
  // The inversemap cannot works without its DescriptorMap because
  // it holds reference to it. 
  const int EDGE = int(NODE * std::log(double(NODE)));
  for (int i = 0; i < EDGE; ++i) {
    int si = rnd[NODE];
    int ti = rnd[NODE];
      
    graph.addEdge(nodeInv[si], nodeInv[ti]);
  }

  GraphWriter<Graph>(std::cout, graph).run();

  std::cout << std::endl;
  std::cout << "Postscript file: descriptor_map_demo.eps" << std::endl;

  // Make postscript from the graph.
    
  CircleMap<Graph> coords(graph, dim2::Point<double>(0.0, 0.0), 10.0);
    
  graphToEps(graph,"descriptor_map_demo.eps").scaleToA4().
    title("Generated graph").
    copyright("(C) 2003-2007 LEMON Project").
    coords(coords).
    nodeScale(1.0).
    enableParallel().parEdgeDist(1).
    drawArrows().arrowWidth(1).arrowLength(1).
    run();
 
  return 0;
}