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kpeter (Peter Kovacs)
kpeter@inf.elte.hu
Improve arc mixing in NS and enable it by default (#391)
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1 file changed with 7 insertions and 6 deletions:
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Ignore white space 48 line context
... ...
@@ -615,53 +615,54 @@
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      search_end:
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        // Make heap of the candidate list (approximating a partial sort)
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        make_heap( _candidates.begin(), _candidates.begin() + _curr_length,
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                   _sort_func );
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        // Pop the first element of the heap
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        _in_arc = _candidates[0];
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        _next_arc = e;
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        pop_heap( _candidates.begin(), _candidates.begin() + _curr_length,
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                  _sort_func );
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        _curr_length = std::min(_head_length, _curr_length - 1);
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        return true;
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      }
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    }; //class AlteringListPivotRule
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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 graph The digraph the algorithm runs on.
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    /// \param arc_mixing Indicate if the arcs have to be stored in a
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    /// \param arc_mixing Indicate if the arcs will be stored in a
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    /// mixed order in the internal data structure.
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    /// In special cases, it could lead to better overall performance,
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    /// but it is usually slower. Therefore it is disabled by default.
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    NetworkSimplex(const GR& graph, bool arc_mixing = false) :
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    /// In general, it leads to similar performance as using the original
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    /// arc order, but it makes the algorithm more robust and in special
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    /// cases, even significantly faster. Therefore, it is enabled by default.
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    NetworkSimplex(const GR& graph, bool arc_mixing = true) :
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      _graph(graph), _node_id(graph), _arc_id(graph),
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      _arc_mixing(arc_mixing),
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      MAX(std::numeric_limits<Value>::max()),
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      INF(std::numeric_limits<Value>::has_infinity ?
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          std::numeric_limits<Value>::infinity() : MAX)
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    {
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      // Check the number types
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      LEMON_ASSERT(std::numeric_limits<Value>::is_signed,
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        "The flow type of NetworkSimplex must be signed");
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      LEMON_ASSERT(std::numeric_limits<Cost>::is_signed,
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        "The cost type of NetworkSimplex must be signed");
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      // Reset data structures
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      reset();
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    }
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    /// \name Parameters
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    /// The parameters of the algorithm can be specified using these
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    /// functions.
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    /// @{
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    /// \brief Set the lower bounds on the arcs.
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    ///
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@@ -909,55 +910,55 @@
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      _lower.resize(_arc_num);
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      _upper.resize(_arc_num);
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      _cap.resize(max_arc_num);
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      _cost.resize(max_arc_num);
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      _supply.resize(all_node_num);
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      _flow.resize(max_arc_num);
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      _pi.resize(all_node_num);
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      _parent.resize(all_node_num);
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      _pred.resize(all_node_num);
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      _pred_dir.resize(all_node_num);
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      _thread.resize(all_node_num);
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      _rev_thread.resize(all_node_num);
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      _succ_num.resize(all_node_num);
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      _last_succ.resize(all_node_num);
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      _state.resize(max_arc_num);
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      // Copy the graph
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      int i = 0;
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      for (NodeIt n(_graph); n != INVALID; ++n, ++i) {
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        _node_id[n] = i;
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      }
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      if (_arc_mixing) {
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        // Store the arcs in a mixed order
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        int k = std::max(int(std::sqrt(double(_arc_num))), 10);
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        const int skip = std::max(_arc_num / _node_num, 3);
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        int i = 0, j = 0;
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        for (ArcIt a(_graph); a != INVALID; ++a) {
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          _arc_id[a] = i;
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          _source[i] = _node_id[_graph.source(a)];
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          _target[i] = _node_id[_graph.target(a)];
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          if ((i += k) >= _arc_num) i = ++j;
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          if ((i += skip) >= _arc_num) i = ++j;
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        }
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      } else {
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        // Store the arcs in the original order
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        int i = 0;
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        for (ArcIt a(_graph); a != INVALID; ++a, ++i) {
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          _arc_id[a] = i;
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          _source[i] = _node_id[_graph.source(a)];
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          _target[i] = _node_id[_graph.target(a)];
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        }
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      }
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      // Reset parameters
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      resetParams();
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      return *this;
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    }
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    /// @}
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    /// \name Query Functions
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    /// The results of the algorithm can be obtained using these
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    /// functions.\n
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    /// The \ref run() function must be called before using them.
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    /// @{
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