permlib 0.2.9
Library for permutation computations
Loading...
Searching...
No Matches
group_intersection_predicate.h
1// ---------------------------------------------------------------------------
2//
3// This file is part of PermLib.
4//
5// Copyright (c) 2009-2011 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 GROUPINTERSECTIONPREDICATE_H_
34#define GROUPINTERSECTIONPREDICATE_H_
35
36#include <permlib/bsgs.h>
37#include <permlib/predicate/subgroup_predicate.h>
38
39#include <boost/foreach.hpp>
40
41namespace permlib {
42
44template <class PERM, class TRANS>
46public:
48
53
54 virtual bool operator()(const PERM &p) const;
55 virtual bool childRestriction(const PERM &h, unsigned int i, unsigned long beta_i) const;
56 virtual unsigned int limit() const;
57private:
58 const BSGS<PERM, TRANS> &m_G;
59 const BSGS<PERM, TRANS> &m_H;
60};
61
62//
63// ---- IMPLEMENTATION
64//
65
66template <class PERM, class TRANS>
68 : m_G(g), m_H(h)
69{
70 BOOST_ASSERT(m_G.n == m_H.n);
71 BOOST_ASSERT(m_G.order() <= m_H.order());
72}
73
74template <class PERM, class TRANS>
76 return m_G.sifts(p) && m_H.sifts(p);
77}
78
79template <class PERM, class TRANS>
80bool GroupIntersectionPredicate<PERM,TRANS>::childRestriction(const PERM &h, unsigned int i, unsigned long beta_i) const {
81 //TODO: check \beta_l^{g h^{-1}} \in \beta_l^{H_{(beta_1 ... beta_{l-1})}} instead
82 // cf. Handbook of Computational Group Theory, sec 4.6.6
83 PERM siftee(m_H.n);
84 const unsigned int m = m_H.sift(h, siftee, 0, i+1);
85 return i+1 == m;
86}
87
88template <class PERM, class TRANS>
90 return m_G.B.size();
91}
92
93}
94
95#endif // -- GROUPINTERSECTIONPREDICATE_H_
predicate for the subgroup that arises as the intersection of two given groups
Definition group_intersection_predicate.h:45
GroupIntersectionPredicate(const BSGS< PERM, TRANS > &g, const BSGS< PERM, TRANS > &h)
constructor
Definition group_intersection_predicate.h:67
virtual unsigned int limit() const
limit of recursion depth in backtrack search
Definition group_intersection_predicate.h:89
virtual bool operator()(const PERM &p) const
true iff group element fulfills predicate
Definition group_intersection_predicate.h:75
virtual bool childRestriction(const PERM &h, unsigned int i, unsigned long beta_i) const
checks if a given group element should not be followed in backtrack search
Definition group_intersection_predicate.h:80
abstract base class for subgroup (and coset) predicates
Definition subgroup_predicate.h:45
Represents a base and strong generating set (BSGS)
Definition bsgs.h:89