permlib 0.2.9
Library for permutation computations
Loading...
Searching...
No Matches
type_recognition_heuristic.h
1// ---------------------------------------------------------------------------
2//
3// This file is part of PermLib.
4//
5// Copyright (c) 2009-2012 Thomas Rehn <thomas@carmen76.de>
6// All rights reserved.
7//
8// Redistribution and use in source and binary forms, with or without
9// modification, are permitted provided that the following conditions
10// are met:
11// 1. Redistributions of source code must retain the above copyright
12// notice, this list of conditions and the following disclaimer.
13// 2. Redistributions in binary form must reproduce the above copyright
14// notice, this list of conditions and the following disclaimer in the
15// documentation and/or other materials provided with the distribution.
16// 3. The name of the author may not be used to endorse or promote products
17// derived from this software without specific prior written permission.
18//
19// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29//
30// ---------------------------------------------------------------------------
31
32
33#ifndef TYPERECOGNITIONHEURISTIC_H_
34#define TYPERECOGNITIONHEURISTIC_H_
35
36#include <list>
37#include <vector>
38
39#include <boost/iterator/counting_iterator.hpp>
40#include <boost/pending/disjoint_sets.hpp>
41
42namespace permlib {
43
45
49template <class PERM>
51public:
56 SymmetricGroupRecognitionHeuristic(unsigned int n, bool storeUnusedGenerators = false);
57
59
63 bool addGenerator(const PERM& p);
65
68 void symmetricGroupOrbits(std::vector<std::list<dom_int> >& orbits);
69
71 const std::list<PERM>& unusedGenerators() { return m_unusedGenerators; }
72private:
73 bool addUnusedGenerator(const PERM& p);
74
75 unsigned int m_n;
76 bool m_storeUnusedGenerators;
77 std::list<PERM> m_unusedGenerators;
78
79 std::vector<dom_int> m_rank;
80 std::vector<dom_int> m_parent;
81 boost::disjoint_sets<dom_int*,dom_int*> m_components;
82
83};
84
85//
86// ---- IMPLEMENTATION
87//
88
89template <class PERM>
91 : m_n(n), m_storeUnusedGenerators(storeUnusedGenerators), m_rank(n), m_parent(n), m_components(&m_rank[0], &m_parent[0])
92{
93 for (dom_int i = 0; i < n; ++i)
94 m_components.make_set(i);
95}
96
97
98template <class PERM>
100 BOOST_ASSERT( p.size() == m_n );
101
102 dom_int cycle[2];
103 unsigned int cycleIndex = 0;
104
105 for (unsigned int i = 0; i < p.size(); ++i) {
106 if (p.at(i) != i) {
107 if (cycleIndex >= 2)
108 return addUnusedGenerator(p);
109
110 cycle[cycleIndex++] = i;
111 }
112 }
113
114 if (cycleIndex == 0)
115 // discard identity
116 return true;
117
118 BOOST_ASSERT(cycleIndex == 2);
119
120 m_components.union_set(cycle[0], cycle[1]);
121 return true;
122}
123
124
125template <class PERM>
126void SymmetricGroupRecognitionHeuristic<PERM>::symmetricGroupOrbits(std::vector<std::list<dom_int> >& orbits) {
127 m_components.compress_sets(boost::counting_iterator<dom_int>(0), boost::counting_iterator<dom_int>(m_n));
128
129 std::vector<unsigned int> componentSizes(m_n);
130 for (unsigned int i = 0; i < m_n; ++i) {
131 ++componentSizes[ m_components.find_set(i) ];
132 }
133
134 std::vector<int> nonTrivialComponentMap(m_n, -1);
135 unsigned int nonTrivialIndex = 0;
136 for (unsigned int i = 0; i < m_n; ++i) {
137 if (componentSizes[i] > 1)
138 nonTrivialComponentMap[i] = nonTrivialIndex++;
139 }
140
141 orbits.clear();
142 orbits.resize(nonTrivialIndex);
143
144 for (unsigned int i = 0; i < m_n; ++i) {
145 unsigned int componentIndex = m_components.find_set(i);
146 if (nonTrivialComponentMap[componentIndex] >= 0)
147 orbits[ nonTrivialComponentMap[componentIndex] ].push_back(i);
148 }
149}
150
151
152template <class PERM>
154 m_unusedGenerators.push_back(p);
155 return false;
156}
157
158} // end NS
159
160#endif // -- TYPERECOGNITIONHEURISTIC_H_
Fast recognition of symmetric group subgroups.
Definition type_recognition_heuristic.h:50
void symmetricGroupOrbits(std::vector< std::list< dom_int > > &orbits)
computes the orbits of recognized non-trivial symmetric subgroups
Definition type_recognition_heuristic.h:126
SymmetricGroupRecognitionHeuristic(unsigned int n, bool storeUnusedGenerators=false)
Definition type_recognition_heuristic.h:90
const std::list< PERM > & unusedGenerators()
returns the list of all group generators that were not used for group recognition
Definition type_recognition_heuristic.h:71
bool addGenerator(const PERM &p)
adds a group generator for recognition
Definition type_recognition_heuristic.h:99