PermLib
type_recognition_heuristic.h
00001 // ---------------------------------------------------------------------------
00002 //
00003 //  This file is part of PermLib.
00004 //
00005 // Copyright (c) 2009-2012 Thomas Rehn <thomas@carmen76.de>
00006 // All rights reserved.
00007 // 
00008 // Redistribution and use in source and binary forms, with or without
00009 // modification, are permitted provided that the following conditions
00010 // are met:
00011 // 1. Redistributions of source code must retain the above copyright
00012 //    notice, this list of conditions and the following disclaimer.
00013 // 2. Redistributions in binary form must reproduce the above copyright
00014 //    notice, this list of conditions and the following disclaimer in the
00015 //    documentation and/or other materials provided with the distribution.
00016 // 3. The name of the author may not be used to endorse or promote products
00017 //    derived from this software without specific prior written permission.
00018 // 
00019 // THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
00020 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00021 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
00022 // IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
00023 // INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
00024 // NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
00025 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
00026 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
00027 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
00028 // THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00029 //
00030 // ---------------------------------------------------------------------------
00031 
00032 
00033 #ifndef TYPERECOGNITIONHEURISTIC_H_
00034 #define TYPERECOGNITIONHEURISTIC_H_
00035 
00036 #include <list>
00037 #include <vector>
00038 
00039 #include <boost/iterator/counting_iterator.hpp>
00040 #include <boost/pending/disjoint_sets.hpp>
00041 
00042 namespace permlib {
00043 
00045 
00049 template <class PERM>
00050 class SymmetricGroupRecognitionHeuristic {
00051 public:
00056         SymmetricGroupRecognitionHeuristic(unsigned int n, bool storeUnusedGenerators = false);
00057         
00059 
00063         bool addGenerator(const PERM& p);
00065 
00068         void symmetricGroupOrbits(std::vector<std::list<dom_int> >& orbits);
00069         
00071         const std::list<PERM>& unusedGenerators() { return m_unusedGenerators; }
00072 private:
00073         bool addUnusedGenerator(const PERM& p);
00074         
00075         unsigned int m_n;
00076         bool m_storeUnusedGenerators;
00077         std::list<PERM> m_unusedGenerators;
00078         
00079         std::vector<dom_int> m_rank;
00080         std::vector<dom_int> m_parent;
00081         boost::disjoint_sets<dom_int*,dom_int*> m_components;
00082         
00083 };
00084 
00085 //
00086 //     ----       IMPLEMENTATION
00087 //
00088 
00089 template <class PERM>
00090 SymmetricGroupRecognitionHeuristic<PERM>::SymmetricGroupRecognitionHeuristic(unsigned int n, bool storeUnusedGenerators) 
00091         : m_n(n), m_storeUnusedGenerators(storeUnusedGenerators), m_rank(n), m_parent(n), m_components(&m_rank[0], &m_parent[0])
00092 { 
00093         for (dom_int i = 0; i < n; ++i)
00094                 m_components.make_set(i);
00095 }
00096 
00097 
00098 template <class PERM>
00099 bool SymmetricGroupRecognitionHeuristic<PERM>::addGenerator(const PERM& p) {
00100         BOOST_ASSERT( p.size() == m_n );
00101         
00102         dom_int cycle[2];
00103         unsigned int cycleIndex = 0;
00104         
00105         for (unsigned int i = 0; i < p.size(); ++i) {
00106                 if (p.at(i) != i) {
00107                         if (cycleIndex >= 2)
00108                                 return addUnusedGenerator(p);
00109                         
00110                         cycle[cycleIndex++] = i;
00111                 }
00112         }
00113         
00114         if (cycleIndex == 0)
00115                 // discard identity
00116                 return true;
00117         
00118         BOOST_ASSERT(cycleIndex == 2);
00119         
00120         m_components.union_set(cycle[0], cycle[1]);
00121         return true;
00122 }
00123 
00124 
00125 template <class PERM>
00126 void SymmetricGroupRecognitionHeuristic<PERM>::symmetricGroupOrbits(std::vector<std::list<dom_int> >& orbits) {
00127         m_components.compress_sets(boost::counting_iterator<dom_int>(0), boost::counting_iterator<dom_int>(m_n));
00128         
00129         std::vector<unsigned int> componentSizes(m_n);
00130         for (unsigned int i = 0; i < m_n; ++i) {
00131                 ++componentSizes[ m_components.find_set(i) ];
00132         }
00133         
00134         std::vector<int> nonTrivialComponentMap(m_n, -1);
00135         unsigned int nonTrivialIndex = 0;
00136         for (unsigned int i = 0; i < m_n; ++i) {
00137                 if (componentSizes[i] > 1)
00138                         nonTrivialComponentMap[i] = nonTrivialIndex++;
00139         }
00140         
00141         orbits.clear();
00142         orbits.resize(nonTrivialIndex);
00143         
00144         for (unsigned int i = 0; i < m_n; ++i) {
00145                 unsigned int componentIndex = m_components.find_set(i);
00146                 if (nonTrivialComponentMap[componentIndex] >= 0)
00147                         orbits[ nonTrivialComponentMap[componentIndex] ].push_back(i);
00148         }
00149 }
00150 
00151 
00152 template <class PERM>
00153 bool SymmetricGroupRecognitionHeuristic<PERM>::addUnusedGenerator(const PERM& p) {
00154         m_unusedGenerators.push_back(p);
00155         return false;
00156 }
00157 
00158 } // end NS
00159 
00160 #endif // -- TYPERECOGNITIONHEURISTIC_H_