001/*
002 * SonarQube, open source software quality management tool.
003 * Copyright (C) 2008-2013 SonarSource
004 * mailto:contact AT sonarsource DOT com
005 *
006 * SonarQube is free software; you can redistribute it and/or
007 * modify it under the terms of the GNU Lesser General Public
008 * License as published by the Free Software Foundation; either
009 * version 3 of the License, or (at your option) any later version.
010 *
011 * SonarQube is distributed in the hope that it will be useful,
012 * but WITHOUT ANY WARRANTY; without even the implied warranty of
013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014 * Lesser General Public License for more details.
015 *
016 * You should have received a copy of the GNU Lesser General Public License
017 * along with this program; if not, write to the Free Software Foundation,
018 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
019 */
020package org.sonar.graph;
021
022import java.util.*;
023
024public class MinimumFeedbackEdgeSetSolver {
025
026  private final List<FeedbackCycle> feedbackCycles;
027  private Set<FeedbackEdge> feedbackEdges;
028  private int minimumFeedbackEdgesWeight = Integer.MAX_VALUE;
029  private final int cyclesNumber;
030  private final int maxNumberCyclesForSearchingMinimumFeedback;
031  private static final int DEFAULT_MAXIMUM_NUMBER_OF_LOOPS = 1000000;
032  private static final int MAXIMUM_NUMBER_OF_CYCLE_THAT_CAN_BE_HANDLED = 1500;
033  private final int maximumNumberOfLoops;
034
035  public int getNumberOfLoops() {
036    return numberOfLoops;
037  }
038
039  private int numberOfLoops = 0;
040
041  public MinimumFeedbackEdgeSetSolver(Set<Cycle> cycles, int maxCycles) {
042    this(cycles, DEFAULT_MAXIMUM_NUMBER_OF_LOOPS, maxCycles);
043  }
044
045  public MinimumFeedbackEdgeSetSolver(Set<Cycle> cycles) {
046    this(cycles, DEFAULT_MAXIMUM_NUMBER_OF_LOOPS, MAXIMUM_NUMBER_OF_CYCLE_THAT_CAN_BE_HANDLED);
047  }
048
049  public MinimumFeedbackEdgeSetSolver(Set<Cycle> cycles, int maximumNumberOfLoops, int maxNumberCyclesForSearchingMinimumFeedback) {
050    this.maximumNumberOfLoops = maximumNumberOfLoops;
051    this.feedbackCycles = FeedbackCycle.buildFeedbackCycles(cycles);
052    this.cyclesNumber = cycles.size();
053    this.maxNumberCyclesForSearchingMinimumFeedback = maxNumberCyclesForSearchingMinimumFeedback;
054    this.run();
055  }
056
057  public int getWeightOfFeedbackEdgeSet() {
058    return minimumFeedbackEdgesWeight;
059  }
060
061  /**
062   * Get edges tagged as feedback.
063   */
064  public Set<Edge> getEdges() {
065    Set<Edge> edges = new HashSet<Edge>();
066    for (FeedbackEdge fe : feedbackEdges) {
067      edges.add(fe.getEdge());
068    }
069    return edges;
070  }
071
072  private void run() {
073    Set<FeedbackEdge> pendingFeedbackEdges = new HashSet<FeedbackEdge>();
074    if (cyclesNumber < maxNumberCyclesForSearchingMinimumFeedback) {
075      searchFeedbackEdges(0, 0, pendingFeedbackEdges);
076    } else {
077      lightResearchForFeedbackEdges();
078    }
079  }
080
081  private void lightResearchForFeedbackEdges() {
082    feedbackEdges = new HashSet<FeedbackEdge>();
083    for (FeedbackCycle cycle : feedbackCycles) {
084      for (FeedbackEdge edge : cycle) {
085        feedbackEdges.add(edge);
086        break;
087      }
088    }
089    minimumFeedbackEdgesWeight = 0;
090    for(FeedbackEdge edge : feedbackEdges) {
091      minimumFeedbackEdgesWeight += edge.getWeight();
092    }
093  }
094
095  private void searchFeedbackEdges(int level, int pendingWeight, Set<FeedbackEdge> pendingFeedbackEdges) {
096    if (numberOfLoops++ > maximumNumberOfLoops) {
097      return;
098    }
099
100    if (pendingWeight >= minimumFeedbackEdgesWeight) {
101      return;
102    }
103
104    if (level == cyclesNumber) {
105      minimumFeedbackEdgesWeight = pendingWeight;
106      feedbackEdges = new HashSet<FeedbackEdge>(pendingFeedbackEdges);
107      return;
108    }
109
110    FeedbackCycle feedbackCycle = feedbackCycles.get(level);
111
112    if (doesFeedbackEdgesContainAnEdgeOfTheCycle(pendingFeedbackEdges, feedbackCycle)) {
113      searchFeedbackEdges(level + 1, pendingWeight, pendingFeedbackEdges);
114    } else {
115      boolean hasAnEdgeWithOccurrenceOfOneBeenUsed = false;
116      for (FeedbackEdge feedbackEdge : feedbackCycle) {
117        if (feedbackEdge.getOccurences() == 1) {
118          if (hasAnEdgeWithOccurrenceOfOneBeenUsed) {
119            continue;
120          } else {
121            hasAnEdgeWithOccurrenceOfOneBeenUsed = true;
122          }
123        }
124        int edgeWeight = addNewEdge(feedbackEdge, pendingFeedbackEdges);
125        pendingWeight += edgeWeight;
126
127        searchFeedbackEdges(level + 1, pendingWeight, pendingFeedbackEdges);
128        pendingWeight -= edgeWeight;
129        pendingFeedbackEdges.remove(feedbackEdge);
130      }
131    }
132  }
133
134  private boolean doesFeedbackEdgesContainAnEdgeOfTheCycle(Set<FeedbackEdge> pendingFeedbackEdges, FeedbackCycle cycle) {
135    boolean contains = false;
136    for (FeedbackEdge feedbackEdge : cycle) {
137      if (pendingFeedbackEdges.contains(feedbackEdge)) {
138        contains = true;
139        break;
140      }
141    }
142    return contains;
143  }
144
145  private int addNewEdge(FeedbackEdge feedbackEdge, Set<FeedbackEdge> pendingFeedbackEdges) {
146    pendingFeedbackEdges.add(feedbackEdge);
147    return feedbackEdge.getWeight();
148  }
149}