boost/graph/relax.hpp
//
//=======================================================================
// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
//
// This file is part of the Boost Graph Library
//
// You should have received a copy of the License Agreement for the
// Boost Graph Library along with the software; see the file LICENSE.
// If not, contact Office of Research, University of Notre Dame, Notre
// Dame, IN 46556.
//
// Permission to modify the code and to distribute modified code is
// granted, provided the text of this NOTICE is retained, a notice that
// the code was modified is included with the above COPYRIGHT NOTICE and
// with the COPYRIGHT NOTICE in the LICENSE file, and that the LICENSE
// file is distributed with the modified code.
//
// LICENSOR MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.
// By way of example, but not limitation, Licensor MAKES NO
// REPRESENTATIONS OR WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY
// PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE COMPONENTS
// OR DOCUMENTATION WILL NOT INFRINGE ANY PATENTS, COPYRIGHTS, TRADEMARKS
// OR OTHER RIGHTS.
//=======================================================================
//
#ifndef BOOST_GRAPH_RELAX_HPP
#define BOOST_GRAPH_RELAX_HPP
#include <functional>
#include <boost/limits.hpp> // for numeric limits
#include <boost/graph/graph_traits.hpp>
#include <boost/property_map.hpp>
namespace boost {
// The following version of the plus functor prevents
// problems due to overflow at positive infinity.
template <class T>
struct closed_plus
{
// std::abs just isn't portable :(
template <class X>
inline X my_abs(const X& x) const { return x < 0 ? -x : x; }
T operator()(const T& a, const T& b) const {
using namespace std;
T inf = (numeric_limits<T>::max)();
if (b > 0 && my_abs(inf - a) < b)
return inf;
return a + b;
}
};
template <class Graph, class WeightMap,
class PredecessorMap, class DistanceMap,
class BinaryFunction, class BinaryPredicate>
bool relax(typename graph_traits<Graph>::edge_descriptor e,
const Graph& g, const WeightMap& w,
PredecessorMap& p, DistanceMap& d,
const BinaryFunction& combine, const BinaryPredicate& compare)
{
typedef typename graph_traits<Graph>::directed_category DirCat;
bool is_undirected = is_same<DirCat, undirected_tag>::value;
typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
Vertex u = source(e, g), v = target(e, g);
typedef typename property_traits<DistanceMap>::value_type D;
typedef typename property_traits<WeightMap>::value_type W;
D d_u = get(d, u), d_v = get(d, v);
W w_e = get(w, e);
if ( compare(combine(d_u, w_e), d_v) ) {
put(d, v, combine(d_u, w_e));
put(p, v, u);
return true;
} else if (is_undirected && compare(combine(d_v, w_e), d_u)) {
put(d, u, combine(d_v, w_e));
put(p, u, v);
return true;
} else
return false;
}
template <class Graph, class WeightMap,
class PredecessorMap, class DistanceMap>
bool relax(typename graph_traits<Graph>::edge_descriptor e,
const Graph& g, WeightMap w, PredecessorMap p, DistanceMap d)
{
typedef typename property_traits<DistanceMap>::value_type D;
typedef closed_plus<D> Combine;
typedef std::less<D> Compare;
return relax(e, g, w, p, d, Combine(), Compare());
}
} // namespace boost
#endif /* BOOST_GRAPH_RELAX_HPP */