# Ticket #438: 438-new-21a9f829ab68.patch

File 438-new-21a9f829ab68.patch, 4.5 KB (added by Peter Kovacs, 10 years ago)
• ## lemon/howard_mmc.h

# HG changeset patch
# User Peter Kovacs <kpeter@inf.elte.hu>
# Date 1352959529 -3600
# Node ID 21a9f829ab68555675534cb075253929315be385
# Parent  764826c6e2b451f09cfa6e588a3de005bc308154
Optional iteration limit in HowardMmc (#438)

diff --git a/lemon/howard_mmc.h b/lemon/howard_mmc.h
 a /// The \ref 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); return findCycleMean() && findCycle(); } /// \brief Find the minimum cycle mean. /// \brief Find the minimum cycle mean (or an upper bound). /// /// This function finds the minimum mean cost of the directed /// cycles in the digraph. /// cycles in the digraph (or an upper bound for it). /// /// \return \c true if a directed cycle exists in the digraph. bool findCycleMean() { /// 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::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_size = _curr_size; _best_node = _curr_node; } if (iter_limit_reached) break; } return _best_found; if (iter_limit_reached) { return ITERATION_LIMIT; } else { return _best_found ? OPTIMAL : NO_CYCLE; } } /// \brief Find a minimum mean directed cycle.
• ## test/min_mean_cycle_test.cc

diff --git a/test/min_mean_cycle_test.cc b/test/min_mean_cycle_test.cc
 a const SmartDigraph::ArcMap& cm, int cost, int size) { MMC alg(gr, lm); alg.findCycleMean(); check(alg.findCycleMean(), "Wrong result"); check(alg.cycleMean() == static_cast(cost) / size, "Wrong cycle mean"); alg.findCycle(); checkMmcAlg >(gr, l2, c2,  5, 2); checkMmcAlg >(gr, l3, c3,  0, 1); checkMmcAlg >(gr, l4, c4, -1, 1); // Howard with iteration limit HowardMmc mmc(gr, l1); check((mmc.findCycleMean(2) == HowardMmc::ITERATION_LIMIT), "Wrong termination cause"); check((mmc.findCycleMean(4) == HowardMmc::OPTIMAL), "Wrong termination cause"); } return 0;