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* This software is provided "AS IS" with no warranty of any kind,
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* express or implied, and with no claim as to its suitability for any
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* purpose.
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*
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*/
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#ifndef LEMON_MIN_MEAN_CYCLE_H
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#define LEMON_MIN_MEAN_CYCLE_H
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#ifndef LEMON_HOWARD_H
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#define LEMON_HOWARD_H
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/// \ingroup shortest_path
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///
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/// \file
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/// \brief Howard's algorithm for finding a minimum mean cycle.
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#include <lemon/path.h>
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#include <lemon/tolerance.h>
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#include <lemon/connectivity.h>
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namespace lemon {
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/// \brief Default traits class of MinMeanCycle class.
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/// \brief Default traits class of Howard class.
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///
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/// Default traits class of MinMeanCycle class.
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/// Default traits class of Howard class.
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/// \tparam GR The type of the digraph.
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/// \tparam LEN The type of the length map.
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/// It must conform to the \ref concepts::ReadMap "ReadMap" concept.
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#ifdef DOXYGEN
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template <typename GR, typename LEN>
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#else
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template <typename GR, typename LEN,
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bool integer = std::numeric_limits<typename LEN::Value>::is_integer>
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#endif
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struct MinMeanCycleDefaultTraits
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struct HowardDefaultTraits
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{
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/// The type of the digraph
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typedef GR Digraph;
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/// The type of the length map
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typedef LEN LengthMap;
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/// The type of the arc lengths
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/// and it must have an \c addBack() function.
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typedef lemon::Path<Digraph> Path;
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};
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// Default traits class for integer value types
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template <typename GR, typename LEN>
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struct MinMeanCycleDefaultTraits<GR, LEN, true>
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struct HowardDefaultTraits<GR, LEN, true>
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{
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typedef GR Digraph;
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typedef LEN LengthMap;
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typedef typename LengthMap::Value Value;
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#ifdef LEMON_HAVE_LONG_LONG
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typedef long long LargeValue;
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/// \addtogroup shortest_path
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/// @{
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/// \brief Implementation of Howard's algorithm for finding a minimum
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/// mean cycle.
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///
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/// \ref MinMeanCycle implements Howard's algorithm for finding a
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/// directed cycle of minimum mean length (cost) in a digraph.
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/// This class implements Howard's policy iteration algorithm for finding
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/// a directed cycle of minimum mean length (cost) in a digraph.
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///
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/// \tparam GR The type of the digraph the algorithm runs on.
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/// \tparam LEN The type of the length map. The default
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/// map type is \ref concepts::Digraph::ArcMap "GR::ArcMap<int>".
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#ifdef DOXYGEN
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template <typename GR, typename LEN, typename TR>
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#else
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template < typename GR,
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typename LEN = typename GR::template ArcMap<int>,
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typename TR = MinMeanCycleDefaultTraits<GR, LEN> >
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typename TR = HowardDefaultTraits<GR, LEN> >
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#endif
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class MinMeanCycle
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class Howard
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{
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public:
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/// The type of the digraph
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typedef typename TR::Digraph Digraph;
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/// The type of the length map
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/// The type of the arc lengths
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typedef typename TR::Value Value;
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/// \brief The large value type
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///
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/// The large value type used for internal computations.
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/// Using the \ref MinMeanCycleDefaultTraits "default traits class",
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/// Using the \ref HowardDefaultTraits "default traits class",
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/// it is \c long \c long if the \c Value type is integer,
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/// otherwise it is \c double.
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typedef typename TR::LargeValue LargeValue;
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/// The tolerance type
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typedef typename TR::Tolerance Tolerance;
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/// \brief The path type of the found cycles
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///
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/// The path type of the found cycles.
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/// Using the \ref MinMeanCycleDefaultTraits "default traits class",
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/// Using the \ref HowardDefaultTraits "default traits class",
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/// it is \ref lemon::Path "Path<Digraph>".
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typedef typename TR::Path Path;
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/// The \ref MinMeanCycleDefaultTraits "traits class" of the algorithm
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/// The \ref HowardDefaultTraits "traits class" of the algorithm
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typedef TR Traits;
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private:
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TEMPLATE_DIGRAPH_TYPEDEFS(Digraph);
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/// \c LargeValue type.
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///
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/// \ref named-templ-param "Named parameter" for setting \c LargeValue
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/// type. It is used for internal computations in the algorithm.
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template <typename T>
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struct SetLargeValue
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: public MinMeanCycle<GR, LEN, SetLargeValueTraits<T> > {
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typedef MinMeanCycle<GR, LEN, SetLargeValueTraits<T> > Create;
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: public Howard<GR, LEN, SetLargeValueTraits<T> > {
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typedef Howard<GR, LEN, SetLargeValueTraits<T> > Create;
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};
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template <typename T>
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struct SetPathTraits : public Traits {
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typedef T Path;
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};
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/// \ref named-templ-param "Named parameter" for setting the \c %Path
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/// type of the found cycles.
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/// It must conform to the \ref lemon::concepts::Path "Path" concept
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/// and it must have an \c addBack() function.
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template <typename T>
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struct SetPath
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: public MinMeanCycle<GR, LEN, SetPathTraits<T> > {
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typedef MinMeanCycle<GR, LEN, SetPathTraits<T> > Create;
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: public Howard<GR, LEN, SetPathTraits<T> > {
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typedef Howard<GR, LEN, SetPathTraits<T> > Create;
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};
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/// @}
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public:
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/// \brief Constructor.
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///
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/// The constructor of the class.
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///
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/// \param digraph The digraph the algorithm runs on.
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/// \param length The lengths (costs) of the arcs.
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MinMeanCycle( const Digraph &digraph,
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const LengthMap &length ) :
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Howard( const Digraph &digraph,
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const LengthMap &length ) :
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_gr(digraph), _length(length), _cycle_path(NULL), _local_path(false),
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_policy(digraph), _reached(digraph), _level(digraph), _dist(digraph),
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_comp(digraph), _in_arcs(digraph)
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{}
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/// Destructor.
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~MinMeanCycle() {
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~Howard() {
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if (_local_path) delete _cycle_path;
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}
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/// \brief Set the path structure for storing the found cycle.
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///
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/// This function sets an external path structure for storing the
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/// allocated object, of course.
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///
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/// \note The algorithm calls only the \ref lemon::Path::addBack()
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/// "addBack()" function of the given path structure.
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///
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/// \return <tt>(*this)</tt>
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MinMeanCycle& cycle(Path &path) {
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Howard& cycle(Path &path) {
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if (_local_path) {
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delete _cycle_path;
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_local_path = false;
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}
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_cycle_path = &path;
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return *this;
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}
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}
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}
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return improved;
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}
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}; //class MinMeanCycle
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}; //class Howard
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///@}
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} //namespace lemon
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#endif //LEMON_MIN_MEAN_CYCLE_H
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#endif //LEMON_HOWARD_H
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