dust3d/thirdparty/QuadriFlow/3rd/lemon-1.3.1/lemon/howard_mmc.h

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/* -*- mode: C++; indent-tabs-mode: nil; -*-
*
* This file is a part of LEMON, a generic C++ optimization library.
*
* Copyright (C) 2003-2013
* 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.
*
*/
#ifndef LEMON_HOWARD_MMC_H
#define LEMON_HOWARD_MMC_H
/// \ingroup min_mean_cycle
///
/// \file
/// \brief Howard's algorithm for finding a minimum mean cycle.
#include <vector>
#include <limits>
#include <lemon/core.h>
#include <lemon/path.h>
#include <lemon/tolerance.h>
#include <lemon/connectivity.h>
namespace lemon {
/// \brief Default traits class of HowardMmc class.
///
/// Default traits class of HowardMmc class.
/// \tparam GR The type of the digraph.
/// \tparam CM The type of the cost map.
/// It must conform to the \ref concepts::ReadMap "ReadMap" concept.
#ifdef DOXYGEN
template <typename GR, typename CM>
#else
template <typename GR, typename CM,
bool integer = std::numeric_limits<typename CM::Value>::is_integer>
#endif
struct HowardMmcDefaultTraits
{
/// The type of the digraph
typedef GR Digraph;
/// The type of the cost map
typedef CM CostMap;
/// The type of the arc costs
typedef typename CostMap::Value Cost;
/// \brief The large cost type used for internal computations
///
/// The large cost type used for internal computations.
/// It is \c long \c long if the \c Cost type is integer,
/// otherwise it is \c double.
/// \c Cost must be convertible to \c LargeCost.
typedef double LargeCost;
/// The tolerance type used for internal computations
typedef lemon::Tolerance<LargeCost> Tolerance;
/// \brief The path type of the found cycles
///
/// The path type of the found cycles.
/// It must conform to the \ref lemon::concepts::Path "Path" concept
/// and it must have an \c addBack() function.
typedef lemon::Path<Digraph> Path;
};
// Default traits class for integer cost types
template <typename GR, typename CM>
struct HowardMmcDefaultTraits<GR, CM, true>
{
typedef GR Digraph;
typedef CM CostMap;
typedef typename CostMap::Value Cost;
#ifdef LEMON_HAVE_LONG_LONG
typedef long long LargeCost;
#else
typedef long LargeCost;
#endif
typedef lemon::Tolerance<LargeCost> Tolerance;
typedef lemon::Path<Digraph> Path;
};
/// \addtogroup min_mean_cycle
/// @{
/// \brief Implementation of Howard's algorithm for finding a minimum
/// mean cycle.
///
/// This class implements Howard's policy iteration algorithm for finding
/// a directed cycle of minimum mean cost in a digraph
/// \cite dasdan98minmeancycle, \cite dasdan04experimental.
/// This class provides the most efficient algorithm for the
/// minimum mean cycle problem, though the best known theoretical
/// bound on its running time is exponential.
///
/// \tparam GR The type of the digraph the algorithm runs on.
/// \tparam CM The type of the cost map. The default
/// map type is \ref concepts::Digraph::ArcMap "GR::ArcMap<int>".
/// \tparam TR The traits class that defines various types used by the
/// algorithm. By default, it is \ref HowardMmcDefaultTraits
/// "HowardMmcDefaultTraits<GR, CM>".
/// In most cases, this parameter should not be set directly,
/// consider to use the named template parameters instead.
#ifdef DOXYGEN
template <typename GR, typename CM, typename TR>
#else
template < typename GR,
typename CM = typename GR::template ArcMap<int>,
typename TR = HowardMmcDefaultTraits<GR, CM> >
#endif
class HowardMmc
{
public:
/// The type of the digraph
typedef typename TR::Digraph Digraph;
/// The type of the cost map
typedef typename TR::CostMap CostMap;
/// The type of the arc costs
typedef typename TR::Cost Cost;
/// \brief The large cost type
///
/// The large cost type used for internal computations.
/// By default, it is \c long \c long if the \c Cost type is integer,
/// otherwise it is \c double.
typedef typename TR::LargeCost LargeCost;
/// The tolerance type
typedef typename TR::Tolerance Tolerance;
/// \brief The path type of the found cycles
///
/// The path type of the found cycles.
/// Using the \ref lemon::HowardMmcDefaultTraits "default traits class",
/// it is \ref lemon::Path "Path<Digraph>".
typedef typename TR::Path Path;
/// The \ref lemon::HowardMmcDefaultTraits "traits class" of the algorithm
typedef TR Traits;
/// \brief Constants for the causes of search termination.
///
/// Enum type containing constants for the different causes of search
/// termination. The \ref findCycleMean() function returns one of
/// these values.
enum TerminationCause {
/// No directed cycle can be found in the digraph.
NO_CYCLE = 0,
/// Optimal solution (minimum cycle mean) is found.
OPTIMAL = 1,
/// The iteration count limit is reached.
ITERATION_LIMIT
};
private:
TEMPLATE_DIGRAPH_TYPEDEFS(Digraph);
// The digraph the algorithm runs on
const Digraph &_gr;
// The cost of the arcs
const CostMap &_cost;
// Data for the found cycles
bool _curr_found, _best_found;
LargeCost _curr_cost, _best_cost;
int _curr_size, _best_size;
Node _curr_node, _best_node;
Path *_cycle_path;
bool _local_path;
// Internal data used by the algorithm
typename Digraph::template NodeMap<Arc> _policy;
typename Digraph::template NodeMap<bool> _reached;
typename Digraph::template NodeMap<int> _level;
typename Digraph::template NodeMap<LargeCost> _dist;
// Data for storing the strongly connected components
int _comp_num;
typename Digraph::template NodeMap<int> _comp;
std::vector<std::vector<Node> > _comp_nodes;
std::vector<Node>* _nodes;
typename Digraph::template NodeMap<std::vector<Arc> > _in_arcs;
// Queue used for BFS search
std::vector<Node> _queue;
int _qfront, _qback;
Tolerance _tolerance;
// Infinite constant
const LargeCost INF;
public:
/// \name Named Template Parameters
/// @{
template <typename T>
struct SetLargeCostTraits : public Traits {
typedef T LargeCost;
typedef lemon::Tolerance<T> Tolerance;
};
/// \brief \ref named-templ-param "Named parameter" for setting
/// \c LargeCost type.
///
/// \ref named-templ-param "Named parameter" for setting \c LargeCost
/// type. It is used for internal computations in the algorithm.
template <typename T>
struct SetLargeCost
: public HowardMmc<GR, CM, SetLargeCostTraits<T> > {
typedef HowardMmc<GR, CM, SetLargeCostTraits<T> > Create;
};
template <typename T>
struct SetPathTraits : public Traits {
typedef T Path;
};
/// \brief \ref named-templ-param "Named parameter" for setting
/// \c %Path type.
///
/// \ref named-templ-param "Named parameter" for setting the \c %Path
/// type of the found cycles.
/// It must conform to the \ref lemon::concepts::Path "Path" concept
/// and it must have an \c addBack() function.
template <typename T>
struct SetPath
: public HowardMmc<GR, CM, SetPathTraits<T> > {
typedef HowardMmc<GR, CM, SetPathTraits<T> > Create;
};
/// @}
protected:
HowardMmc() {}
public:
/// \brief Constructor.
///
/// The constructor of the class.
///
/// \param digraph The digraph the algorithm runs on.
/// \param cost The costs of the arcs.
HowardMmc( const Digraph &digraph,
const CostMap &cost ) :
_gr(digraph), _cost(cost), _best_found(false),
_best_cost(0), _best_size(1), _cycle_path(NULL), _local_path(false),
_policy(digraph), _reached(digraph), _level(digraph), _dist(digraph),
_comp(digraph), _in_arcs(digraph),
INF(std::numeric_limits<LargeCost>::has_infinity ?
std::numeric_limits<LargeCost>::infinity() :
std::numeric_limits<LargeCost>::max())
{}
/// Destructor.
~HowardMmc() {
if (_local_path) delete _cycle_path;
}
/// \brief Set the path structure for storing the found cycle.
///
/// This function sets an external path structure for storing the
/// found cycle.
///
/// If you don't call this function before calling \ref run() or
/// \ref findCycleMean(), a local \ref Path "path" structure
/// will be allocated. The destuctor deallocates this automatically
/// allocated object, of course.
///
/// \note The algorithm calls only the \ref lemon::Path::addBack()
/// "addBack()" function of the given path structure.
///
/// \return <tt>(*this)</tt>
HowardMmc& cycle(Path &path) {
if (_local_path) {
delete _cycle_path;
_local_path = false;
}
_cycle_path = &path;
return *this;
}
/// \brief Set the tolerance used by the algorithm.
///
/// This function sets the tolerance object used by the algorithm.
///
/// \return <tt>(*this)</tt>
HowardMmc& tolerance(const Tolerance& tolerance) {
_tolerance = tolerance;
return *this;
}
/// \brief Return a const reference to the tolerance.
///
/// This function returns a const reference to the tolerance object
/// used by the algorithm.
const Tolerance& tolerance() const {
return _tolerance;
}
/// \name Execution control
/// The simplest way to execute the algorithm is to call the \ref run()
/// function.\n
/// If you only need the minimum mean cost, you may call
/// \ref findCycleMean().
/// @{
/// \brief Run the algorithm.
///
/// This function runs the algorithm.
/// It can be called more than once (e.g. if the underlying digraph
/// and/or the arc costs have been modified).
///
/// \return \c true if a directed cycle exists in the digraph.
///
/// \note <tt>mmc.run()</tt> is just a shortcut of the following code.
/// \code
/// return mmc.findCycleMean() && mmc.findCycle();
/// \endcode
bool run() {
return findCycleMean() && findCycle();
}
/// \brief Find the minimum cycle mean (or an upper bound).
///
/// This function finds the minimum mean cost of the directed
/// cycles in the digraph (or an upper bound for it).
///
/// By default, the function finds the exact minimum cycle mean,
/// but an optional limit can also be specified for the number of
/// iterations performed during the search process.
/// The return value indicates if the optimal solution is found
/// or the iteration limit is reached. In the latter case, an
/// approximate solution is provided, which corresponds to a directed
/// cycle whose mean cost is relatively small, but not necessarily
/// minimal.
///
/// \param limit The maximum allowed number of iterations during
/// the search process. Its default value implies that the algorithm
/// runs until it finds the exact optimal solution.
///
/// \return The termination cause of the search process.
/// For more information, see \ref TerminationCause.
TerminationCause findCycleMean(int limit =
std::numeric_limits<int>::max()) {
// Initialize and find strongly connected components
init();
findComponents();
// Find the minimum cycle mean in the components
int iter_count = 0;
bool iter_limit_reached = false;
for (int comp = 0; comp < _comp_num; ++comp) {
// Find the minimum mean cycle in the current component
if (!buildPolicyGraph(comp)) continue;
while (true) {
if (++iter_count > limit) {
iter_limit_reached = true;
break;
}
findPolicyCycle();
if (!computeNodeDistances()) break;
}
// Update the best cycle (global minimum mean cycle)
if ( _curr_found && (!_best_found ||
_curr_cost * _best_size < _best_cost * _curr_size) ) {
_best_found = true;
_best_cost = _curr_cost;
_best_size = _curr_size;
_best_node = _curr_node;
}
if (iter_limit_reached) break;
}
if (iter_limit_reached) {
return ITERATION_LIMIT;
} else {
return _best_found ? OPTIMAL : NO_CYCLE;
}
}
/// \brief Find a minimum mean directed cycle.
///
/// This function finds a directed cycle of minimum mean cost
/// in the digraph using the data computed by findCycleMean().
///
/// \return \c true if a directed cycle exists in the digraph.
///
/// \pre \ref findCycleMean() must be called before using this function.
bool findCycle() {
if (!_best_found) return false;
_cycle_path->addBack(_policy[_best_node]);
for ( Node v = _best_node;
(v = _gr.target(_policy[v])) != _best_node; ) {
_cycle_path->addBack(_policy[v]);
}
return true;
}
/// @}
/// \name Query Functions
/// The results of the algorithm can be obtained using these
/// functions.\n
/// The algorithm should be executed before using them.
/// @{
/// \brief Return the total cost of the found cycle.
///
/// This function returns the total cost of the found cycle.
///
/// \pre \ref run() or \ref findCycleMean() must be called before
/// using this function.
Cost cycleCost() const {
return static_cast<Cost>(_best_cost);
}
/// \brief Return the number of arcs on the found cycle.
///
/// This function returns the number of arcs on the found cycle.
///
/// \pre \ref run() or \ref findCycleMean() must be called before
/// using this function.
int cycleSize() const {
return _best_size;
}
/// \brief Return the mean cost of the found cycle.
///
/// This function returns the mean cost of the found cycle.
///
/// \note <tt>alg.cycleMean()</tt> is just a shortcut of the
/// following code.
/// \code
/// return static_cast<double>(alg.cycleCost()) / alg.cycleSize();
/// \endcode
///
/// \pre \ref run() or \ref findCycleMean() must be called before
/// using this function.
double cycleMean() const {
return static_cast<double>(_best_cost) / _best_size;
}
/// \brief Return the found cycle.
///
/// This function returns a const reference to the path structure
/// storing the found cycle.
///
/// \pre \ref run() or \ref findCycle() must be called before using
/// this function.
const Path& cycle() const {
return *_cycle_path;
}
///@}
private:
// Initialize
void init() {
if (!_cycle_path) {
_local_path = true;
_cycle_path = new Path;
}
_queue.resize(countNodes(_gr));
_best_found = false;
_best_cost = 0;
_best_size = 1;
_cycle_path->clear();
}
// Find strongly connected components and initialize _comp_nodes
// and _in_arcs
void findComponents() {
_comp_num = stronglyConnectedComponents(_gr, _comp);
_comp_nodes.resize(_comp_num);
if (_comp_num == 1) {
_comp_nodes[0].clear();
for (NodeIt n(_gr); n != INVALID; ++n) {
_comp_nodes[0].push_back(n);
_in_arcs[n].clear();
for (InArcIt a(_gr, n); a != INVALID; ++a) {
_in_arcs[n].push_back(a);
}
}
} else {
for (int i = 0; i < _comp_num; ++i)
_comp_nodes[i].clear();
for (NodeIt n(_gr); n != INVALID; ++n) {
int k = _comp[n];
_comp_nodes[k].push_back(n);
_in_arcs[n].clear();
for (InArcIt a(_gr, n); a != INVALID; ++a) {
if (_comp[_gr.source(a)] == k) _in_arcs[n].push_back(a);
}
}
}
}
// Build the policy graph in the given strongly connected component
// (the out-degree of every node is 1)
bool buildPolicyGraph(int comp) {
_nodes = &(_comp_nodes[comp]);
if (_nodes->size() < 1 ||
(_nodes->size() == 1 && _in_arcs[(*_nodes)[0]].size() == 0)) {
return false;
}
for (int i = 0; i < int(_nodes->size()); ++i) {
_dist[(*_nodes)[i]] = INF;
}
Node u, v;
Arc e;
for (int i = 0; i < int(_nodes->size()); ++i) {
v = (*_nodes)[i];
for (int j = 0; j < int(_in_arcs[v].size()); ++j) {
e = _in_arcs[v][j];
u = _gr.source(e);
if (_cost[e] < _dist[u]) {
_dist[u] = _cost[e];
_policy[u] = e;
}
}
}
return true;
}
// Find the minimum mean cycle in the policy graph
void findPolicyCycle() {
for (int i = 0; i < int(_nodes->size()); ++i) {
_level[(*_nodes)[i]] = -1;
}
LargeCost ccost;
int csize;
Node u, v;
_curr_found = false;
for (int i = 0; i < int(_nodes->size()); ++i) {
u = (*_nodes)[i];
if (_level[u] >= 0) continue;
for (; _level[u] < 0; u = _gr.target(_policy[u])) {
_level[u] = i;
}
if (_level[u] == i) {
// A cycle is found
ccost = _cost[_policy[u]];
csize = 1;
for (v = u; (v = _gr.target(_policy[v])) != u; ) {
ccost += _cost[_policy[v]];
++csize;
}
if ( !_curr_found ||
(ccost * _curr_size < _curr_cost * csize) ) {
_curr_found = true;
_curr_cost = ccost;
_curr_size = csize;
_curr_node = u;
}
}
}
}
// Contract the policy graph and compute node distances
bool computeNodeDistances() {
// Find the component of the main cycle and compute node distances
// using reverse BFS
for (int i = 0; i < int(_nodes->size()); ++i) {
_reached[(*_nodes)[i]] = false;
}
_qfront = _qback = 0;
_queue[0] = _curr_node;
_reached[_curr_node] = true;
_dist[_curr_node] = 0;
Node u, v;
Arc e;
while (_qfront <= _qback) {
v = _queue[_qfront++];
for (int j = 0; j < int(_in_arcs[v].size()); ++j) {
e = _in_arcs[v][j];
u = _gr.source(e);
if (_policy[u] == e && !_reached[u]) {
_reached[u] = true;
_dist[u] = _dist[v] + _cost[e] * _curr_size - _curr_cost;
_queue[++_qback] = u;
}
}
}
// Connect all other nodes to this component and compute node
// distances using reverse BFS
_qfront = 0;
while (_qback < int(_nodes->size())-1) {
v = _queue[_qfront++];
for (int j = 0; j < int(_in_arcs[v].size()); ++j) {
e = _in_arcs[v][j];
u = _gr.source(e);
if (!_reached[u]) {
_reached[u] = true;
_policy[u] = e;
_dist[u] = _dist[v] + _cost[e] * _curr_size - _curr_cost;
_queue[++_qback] = u;
}
}
}
// Improve node distances
bool improved = false;
for (int i = 0; i < int(_nodes->size()); ++i) {
v = (*_nodes)[i];
for (int j = 0; j < int(_in_arcs[v].size()); ++j) {
e = _in_arcs[v][j];
u = _gr.source(e);
LargeCost delta = _dist[v] + _cost[e] * _curr_size - _curr_cost;
if (_tolerance.less(delta, _dist[u])) {
_dist[u] = delta;
_policy[u] = e;
improved = true;
}
}
}
return improved;
}
}; //class HowardMmc
///@}
} //namespace lemon
#endif //LEMON_HOWARD_MMC_H