[Lemon-commits] deba: r3405 - lemon/trunk/lemon
Lemon SVN
svn at lemon.cs.elte.hu
Wed Nov 28 19:05:49 CET 2007
Author: deba
Date: Wed Nov 28 19:05:49 2007
New Revision: 3405
Added:
lemon/trunk/lemon/gomory_hu_tree.h
Modified:
lemon/trunk/lemon/Makefile.am
Log:
Gomory-Hu tree algorithm
Modified: lemon/trunk/lemon/Makefile.am
==============================================================================
--- lemon/trunk/lemon/Makefile.am (original)
+++ lemon/trunk/lemon/Makefile.am Wed Nov 28 19:05:49 2007
@@ -74,6 +74,7 @@
lemon/graph_writer.h \
lemon/grid_ugraph.h \
lemon/goldberg_tarjan.h \
+ lemon/gomory_hu_tree.h \
lemon/hao_orlin.h \
lemon/hypercube_graph.h \
lemon/iterable_maps.h \
Added: lemon/trunk/lemon/gomory_hu_tree.h
==============================================================================
--- (empty file)
+++ lemon/trunk/lemon/gomory_hu_tree.h Wed Nov 28 19:05:49 2007
@@ -0,0 +1,296 @@
+/* -*- C++ -*-
+ *
+ * This file is a part of LEMON, a generic C++ optimization library
+ *
+ * Copyright (C) 2003-2007
+ * 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_GOMORY_HU_TREE_H
+#define LEMON_GOMORY_HU_TREE_H
+
+#include <lemon/preflow.h>
+#include <lemon/concept_check.h>
+#include <lemon/concepts/maps.h>
+
+/// \ingroup min_cut
+/// \file
+/// \brief Gomory-Hu cut tree in undirected graphs.
+
+namespace lemon {
+
+ /// \ingroup min_cut
+ ///
+ /// \brief Gomory-Hu cut tree algorithm
+ ///
+ /// The Gomory-Hu tree is a tree on the nodeset of the graph, but it
+ /// may contain edges which are not in the original graph. It helps
+ /// to calculate the minimum cut between all pairs of nodes, because
+ /// the minimum capacity edge on the tree path between two nodes has
+ /// the same weight as the minimum cut in the graph between these
+ /// nodes. Moreover this edge separates the nodes to two parts which
+ /// determine this minimum cut.
+ ///
+ /// The algorithm calculates \e n-1 distinict minimum cuts with
+ /// preflow algorithm, therefore the algorithm has
+ /// \f$(O(n^3\sqrt{e})\f$ overall time complexity. It calculates a
+ /// rooted Gomory-Hu tree, the structure of the tree and the weights
+ /// can be obtained with \c predNode() and \c predValue()
+ /// functions. The \c minCutValue() and \c minCutMap() calculates
+ /// the minimum cut and the minimum cut value between any two node
+ /// in the graph.
+ template <typename _UGraph,
+ typename _Capacity = typename _UGraph::template UEdgeMap<int> >
+ class GomoryHuTree {
+ public:
+
+ /// The undirected graph type
+ typedef _UGraph UGraph;
+ /// The capacity on undirected edges
+ typedef _Capacity Capacity;
+ /// The value type of capacities
+ typedef typename Capacity::Value Value;
+
+ private:
+
+ UGRAPH_TYPEDEFS(typename UGraph);
+
+ const UGraph& _ugraph;
+ const Capacity& _capacity;
+
+ Node _root;
+ typename UGraph::template NodeMap<Node>* _pred;
+ typename UGraph::template NodeMap<Value>* _weight;
+ typename UGraph::template NodeMap<int>* _order;
+
+ void createStructures() {
+ if (!_pred) {
+ _pred = new typename UGraph::template NodeMap<Node>(_ugraph);
+ }
+ if (!_weight) {
+ _weight = new typename UGraph::template NodeMap<Value>(_ugraph);
+ }
+ if (!_order) {
+ _order = new typename UGraph::template NodeMap<int>(_ugraph);
+ }
+ }
+
+ void destroyStructures() {
+ if (_pred) {
+ delete _pred;
+ }
+ if (_weight) {
+ delete _weight;
+ }
+ if (_order) {
+ delete _order;
+ }
+ }
+
+ public:
+
+ /// \brief Constructor
+ ///
+ /// Constructor
+ /// \param ugraph The undirected graph type.
+ /// \param capacity The capacity map.
+ GomoryHuTree(const UGraph& ugraph, const Capacity& capacity)
+ : _ugraph(ugraph), _capacity(capacity),
+ _pred(0), _weight(0), _order(0)
+ {
+ checkConcept<concepts::ReadMap<UEdge, Value>, Capacity>();
+ }
+
+
+ /// \brief Destructor
+ ///
+ /// Destructor
+ ~GomoryHuTree() {
+ destroyStructures();
+ }
+
+ /// \brief Initializes the internal data structures.
+ ///
+ /// Initializes the internal data structures.
+ ///
+ void init() {
+ createStructures();
+
+ _root = NodeIt(_ugraph);
+ for (NodeIt n(_ugraph); n != INVALID; ++n) {
+ _pred->set(n, _root);
+ _order->set(n, -1);
+ }
+ _pred->set(_root, INVALID);
+ _weight->set(_root, std::numeric_limits<Value>::max());
+ }
+
+
+ /// \brief Starts the algorithm
+ ///
+ /// Starts the algorithm.
+ void start() {
+ Preflow<UGraph, Capacity> fa(_ugraph, _capacity, _root, INVALID);
+
+ for (NodeIt n(_ugraph); n != INVALID; ++n) {
+ if (n == _root) continue;
+
+ Node pn = (*_pred)[n];
+ fa.source(n);
+ fa.target(pn);
+
+ fa.runMinCut();
+
+ _weight->set(n, fa.flowValue());
+
+ for (NodeIt nn(_ugraph); nn != INVALID; ++nn) {
+ if (nn != n && fa.minCut(nn) && (*_pred)[nn] == pn) {
+ _pred->set(nn, n);
+ }
+ }
+ if ((*_pred)[pn] != INVALID && fa.minCut((*_pred)[pn])) {
+ _pred->set(n, (*_pred)[pn]);
+ _pred->set(pn, n);
+ _weight->set(n, (*_weight)[pn]);
+ _weight->set(pn, fa.flowValue());
+ }
+ }
+
+ _order->set(_root, 0);
+ int index = 1;
+
+ for (NodeIt n(_ugraph); n != INVALID; ++n) {
+ std::vector<Node> st;
+ Node nn = n;
+ while ((*_order)[nn] == -1) {
+ st.push_back(nn);
+ nn = (*_pred)[nn];
+ }
+ while (!st.empty()) {
+ _order->set(st.back(), index++);
+ st.pop_back();
+ }
+ }
+ }
+
+ /// \brief Runs the Gomory-Hu algorithm.
+ ///
+ /// Runs the Gomory-Hu algorithm.
+ /// \note gh.run() is just a shortcut of the following code.
+ /// \code
+ /// ght.init();
+ /// ght.start();
+ /// \endcode
+ void run() {
+ init();
+ start();
+ }
+
+ /// \brief Returns the predecessor node in the Gomory-Hu tree.
+ ///
+ /// Returns the predecessor node in the Gomory-Hu tree. If the node is
+ /// the root of the Gomory-Hu tree, then it returns \c INVALID.
+ Node predNode(const Node& node) {
+ return (*_pred)[node];
+ }
+
+ /// \brief Returns the weight of the predecessor edge in the
+ /// Gomory-Hu tree.
+ ///
+ /// Returns the weight of the predecessor edge in the Gomory-Hu
+ /// tree. If the node is the root of the Gomory-Hu tree, the
+ /// result is undefined.
+ Value predValue(const Node& node) {
+ return (*_weight)[node];
+ }
+
+ /// \brief Returns the minimum cut value between two nodes
+ ///
+ /// Returns the minimum cut value between two nodes. The
+ /// algorithm finds the nearest common ancestor in the Gomory-Hu
+ /// tree and calculates the minimum weight edge on the paths to
+ /// the ancestor.
+ Value minCutValue(const Node& s, const Node& t) const {
+ Node sn = s, tn = t;
+ Value value = std::numeric_limits<Value>::max();
+
+ while (sn != tn) {
+ if ((*_order)[sn] < (*_order)[tn]) {
+ if ((*_weight)[tn] < value) value = (*_weight)[tn];
+ tn = (*_pred)[tn];
+ } else {
+ if ((*_weight)[sn] < value) value = (*_weight)[sn];
+ sn = (*_pred)[sn];
+ }
+ }
+ return value;
+ }
+
+ /// \brief Returns the minimum cut between two nodes
+ ///
+ /// Returns the minimum cut value between two nodes. The
+ /// algorithm finds the nearest common ancestor in the Gomory-Hu
+ /// tree and calculates the minimum weight edge on the paths to
+ /// the ancestor. Then it sets all nodes to the cut determined by
+ /// this edge. The \c cutMap should be \ref concepts::ReadWriteMap
+ /// "ReadWriteMap".
+ template <typename CutMap>
+ Value minCutMap(const Node& s, const Node& t, CutMap& cutMap) const {
+ Node sn = s, tn = t;
+
+ Node rn = INVALID;
+ Value value = std::numeric_limits<Value>::max();
+
+ while (sn != tn) {
+ if ((*_order)[sn] < (*_order)[tn]) {
+ if ((*_weight)[tn] < value) {
+ rn = tn;
+ value = (*_weight)[tn];
+ }
+ tn = (*_pred)[tn];
+ } else {
+ if ((*_weight)[sn] < value) {
+ rn = sn;
+ value = (*_weight)[sn];
+ }
+ sn = (*_pred)[sn];
+ }
+ }
+
+ typename UGraph::template NodeMap<bool> reached(_ugraph, false);
+ reached.set(_root, true);
+ cutMap.set(_root, false);
+ reached.set(rn, true);
+ cutMap.set(rn, true);
+
+ for (NodeIt n(_ugraph); n != INVALID; ++n) {
+ std::vector<Node> st;
+ Node nn = n;
+ while (!reached[nn]) {
+ st.push_back(nn);
+ nn = (*_pred)[nn];
+ }
+ while (!st.empty()) {
+ cutMap.set(st.back(), cutMap[nn]);
+ st.pop_back();
+ }
+ }
+
+ return value;
+ }
+
+ };
+
+}
+
+#endif
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