File: metis.hpp

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// Copyright 2005 The Trustees of Indiana University.

// Use, modification and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)

//  Authors: Douglas Gregor
//           Andrew Lumsdaine
#ifndef BOOST_GRAPH_METIS_HPP
#define BOOST_GRAPH_METIS_HPP

#ifdef BOOST_GRAPH_METIS_NO_INLINE
#  define BOOST_GRAPH_METIS_INLINE_KEYWORD
#else
#  define BOOST_GRAPH_METIS_INLINE_KEYWORD inline
#endif

#include <string>
#include <iostream>
#include <iterator>
#include <utility>
#include <sstream>
#include <exception>
#include <vector>
#include <algorithm>

namespace boost { namespace graph {

class metis_exception : public std::exception {};
class metis_input_exception : public metis_exception {};

class metis_reader
{
 public:
  typedef std::size_t vertices_size_type;
  typedef std::size_t edges_size_type;
  typedef double vertex_weight_type;
  typedef double edge_weight_type;

  class edge_iterator
  {
  public:
    typedef std::input_iterator_tag iterator_category;
    typedef std::pair<vertices_size_type, vertices_size_type> value_type;
    typedef const value_type& reference;
    typedef const value_type* pointer;
    typedef std::ptrdiff_t difference_type;

  private:
    class postincrement_proxy
    {
      postincrement_proxy(const value_type& value) : value(value) { }

    public:
      reference operator*() const { return value; }

    private:
      value_type value;
      friend class edge_iterator;
    };
    
  public:
    edge_iterator& operator++();
    postincrement_proxy operator++(int);

    reference operator*() const { return self->edge; }
    pointer operator->() const { return &self->edge; }

    // Default copy constructor and assignment operator are okay

  private:
    edge_iterator(metis_reader* self);
    void advance(bool skip_initial_read);
    
    metis_reader* self;

    friend class metis_reader;
    friend bool operator==(edge_iterator, edge_iterator);
    friend bool operator!=(edge_iterator, edge_iterator);
  };
  friend class edge_iterator;

  class edge_weight_iterator
  {
  public:
    typedef std::input_iterator_tag iterator_category;
    typedef edge_weight_type value_type;
    typedef const value_type& reference;
    typedef const value_type* pointer;

    // Default copy constructor and assignment operator are okay

    reference operator*() const { return self->edge_weight; }
    pointer operator->() const { return &self->edge_weight; }

    edge_weight_iterator& operator++() { return *this; }
    edge_weight_iterator operator++(int) { return *this; }

  private:
    edge_weight_iterator(metis_reader* self) : self(self) { }

    metis_reader* self;
    
    friend class metis_reader;
  };
  
  metis_reader(std::istream& in) : in(in), edge_weight(1.0) { start(); }

  edge_iterator begin();
  edge_iterator end();
  edge_weight_iterator weight_begin();

  vertices_size_type num_vertices() const { return n_vertices; }
  edges_size_type num_edges() const { return n_edges; }

  std::size_t num_vertex_weights() const { return n_vertex_weights; }

  vertex_weight_type vertex_weight(vertices_size_type v, std::size_t n)
  { return vertex_weights[v*num_vertex_weights() + n]; }

  bool has_edge_weights() const { return edge_weights; }

 private:
  void start();

  // Configuration information
  std::istream& in;

  // Information about the current METIS file
  vertices_size_type n_vertices;
  edges_size_type n_edges;
  std::size_t n_vertex_weights;
  bool edge_weights;

  // Information about the current edge/vertex
  std::istringstream line_in;
  std::pair<vertices_size_type, vertices_size_type> edge;
  std::vector<vertex_weight_type> vertex_weights;
  edge_weight_type edge_weight;    

  friend bool operator==(edge_iterator, edge_iterator);
  friend bool operator!=(edge_iterator, edge_iterator);
};

class metis_distribution
{
 public:  
  typedef int process_id_type;
  typedef std::size_t size_type;
  typedef std::vector<process_id_type>::iterator iterator;

  metis_distribution(std::istream& in, process_id_type my_id);
  
  size_type block_size(process_id_type id, size_type) const;
  process_id_type operator()(size_type n) const { return vertices[n]; }
  size_type local(size_type n) const;
  size_type global(size_type n) const { return global(my_id, n); }
  size_type global(process_id_type id, size_type n) const;

  iterator begin() { return vertices.begin(); }
  iterator end()   { return vertices.end(); }

 private:
  process_id_type my_id;
  std::vector<process_id_type> vertices;
};

#if !defined(BOOST_GRAPH_METIS_NO_INLINE) || defined(BOOST_GRAPH_METIS_SOURCE)
BOOST_GRAPH_METIS_INLINE_KEYWORD
bool operator==(metis_reader::edge_iterator x, metis_reader::edge_iterator y)
{
  return (x.self == y.self
          || (x.self && x.self->edge.first == x.self->num_vertices())
          || (y.self && y.self->edge.first == y.self->num_vertices()));
}

BOOST_GRAPH_METIS_INLINE_KEYWORD
bool operator!=(metis_reader::edge_iterator x, metis_reader::edge_iterator y)
{
  return !(x == y);
}

BOOST_GRAPH_METIS_INLINE_KEYWORD
metis_reader::edge_iterator::edge_iterator(metis_reader* self) 
  : self(self) 
{
  if (self) advance(true);
}

BOOST_GRAPH_METIS_INLINE_KEYWORD
metis_reader::edge_iterator& metis_reader::edge_iterator::operator++()
{
  advance(false);
  return *this;
}

BOOST_GRAPH_METIS_INLINE_KEYWORD
void metis_reader::edge_iterator::advance(bool skip_initial_read)
{
  do {

    if (!skip_initial_read) {
      // Try to read the next edge
      if (self->line_in >> std::ws >> self->edge.second) {
        --self->edge.second;
        if (self->has_edge_weights()) {
          if (!(self->line_in >> self->edge_weight))
            boost::throw_exception(metis_input_exception());
        }
        return;
      }

      // Check if we're done
      ++self->edge.first;
      if (self->edge.first == self->num_vertices())
        return;
    }

    // Find the next line
    std::string line;
    while (getline(self->in, line) && !line.empty() && line[0] == '%') {
      /* Keep reading lines in the loop header... */
    }
    if (!self->in) boost::throw_exception(metis_input_exception());
    self->line_in.str(line);
    self->line_in.clear();

    // Read the next line
    std::size_t weights_left = self->n_vertex_weights;
    vertex_weight_type weight;
    while (weights_left > 0) {
      if (self->line_in >> weight) self->vertex_weights.push_back(weight);
      else boost::throw_exception(metis_input_exception());
      --weights_left;
    }

    // Successive iterations will pick up edges for this vertex.
    skip_initial_read = false;
  } while (true);
}

BOOST_GRAPH_METIS_INLINE_KEYWORD
metis_reader::edge_iterator::postincrement_proxy 
metis_reader::edge_iterator::operator++(int)
{
  postincrement_proxy result(**this);
  ++(*this);
  return result;
}

BOOST_GRAPH_METIS_INLINE_KEYWORD
metis_reader::edge_iterator metis_reader::begin()
{
  if (edge.first != 0) start();
  return edge_iterator(this);
}

BOOST_GRAPH_METIS_INLINE_KEYWORD
metis_reader::edge_iterator metis_reader::end()
{
  return edge_iterator(0);
}

BOOST_GRAPH_METIS_INLINE_KEYWORD
metis_reader::edge_weight_iterator metis_reader::weight_begin()
{
  return edge_weight_iterator(this);
}

BOOST_GRAPH_METIS_INLINE_KEYWORD
void metis_reader::start()
{
  in.seekg(0, std::ios::beg);
  std::string line;
  while (getline(in, line) && !line.empty() && line[0] == '%') {
    /* Keep getting lines in loop header. */
  }

  if (!in || line.empty()) boost::throw_exception(metis_input_exception());

  // Determine number of vertices and edges in the graph
  line_in.str(line);
  if (!(line_in >> n_vertices >> n_edges)) boost::throw_exception(metis_input_exception());

  // Determine whether vertex or edge weights are included in the graph
  int fmt = 0;
  line_in >> fmt;
  n_vertex_weights = fmt / 10;
  edge_weights = (fmt % 10 == 1);
  
  // Determine how many (if any!) vertex weights are included
  if (n_vertex_weights) line_in >> n_vertex_weights;

  // Setup the iteration data structures
  edge_weight = 1.0;
  edge.first = 0;
  edge.second = 0;
  vertex_weights.reserve(n_vertex_weights * num_vertices());
}

metis_distribution::metis_distribution(std::istream& in, process_id_type my_id)
  : my_id(my_id), 
    vertices(std::istream_iterator<process_id_type>(in),
             std::istream_iterator<process_id_type>())
{
}


metis_distribution::size_type 
metis_distribution::block_size(process_id_type id, size_type) const
{
  return std::count(vertices.begin(), vertices.end(), id);
}

metis_distribution::size_type metis_distribution::local(size_type n) const
{
  return std::count(vertices.begin(), vertices.begin() + n, vertices[n]);
}

metis_distribution::size_type 
metis_distribution::global(process_id_type id, size_type n) const
{
  std::vector<process_id_type>::const_iterator i = vertices.begin();
  while (*i != id) ++i;

  while (n > 0) {
    do { ++i; } while (*i != id); 
    --n;
  }

  return i - vertices.begin();
}

#endif

} } // end namespace boost::graph

#endif // BOOST_GRAPH_METIS_HPP