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include
permlib
predicate
group_intersection_predicate.h
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// ---------------------------------------------------------------------------
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//
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// This file is part of PermLib.
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//
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// Copyright (c) 2009-2011 Thomas Rehn <thomas@carmen76.de>
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions
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// are met:
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// 1. Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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// 3. The name of the author may not be used to endorse or promote products
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// derived from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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//
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// ---------------------------------------------------------------------------
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#ifndef GROUPINTERSECTIONPREDICATE_H_
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#define GROUPINTERSECTIONPREDICATE_H_
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#include <permlib/bsgs.h>
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#include <permlib/predicate/subgroup_predicate.h>
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#include <boost/foreach.hpp>
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namespace
permlib {
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template
<
class
PERM,
class
TRANS>
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class
GroupIntersectionPredicate
:
public
SubgroupPredicate
<PERM> {
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public
:
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GroupIntersectionPredicate
(
const
BSGS<PERM, TRANS>
&g,
const
BSGS<PERM, TRANS>
&h);
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virtual
bool
operator()
(
const
PERM &p)
const
;
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virtual
bool
childRestriction
(
const
PERM &h,
unsigned
int
i,
unsigned
long
beta_i)
const
;
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virtual
unsigned
int
limit
()
const
;
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private
:
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const
BSGS<PERM, TRANS>
&m_G;
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const
BSGS<PERM, TRANS>
&m_H;
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};
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//
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// ---- IMPLEMENTATION
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//
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template
<
class
PERM,
class
TRANS>
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GroupIntersectionPredicate<PERM,TRANS>::GroupIntersectionPredicate
(
const
BSGS<PERM, TRANS>
&g,
const
BSGS<PERM, TRANS>
&h)
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: m_G(g), m_H(h)
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{
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BOOST_ASSERT(m_G.n == m_H.n);
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BOOST_ASSERT(m_G.order() <= m_H.order());
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}
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template
<
class
PERM,
class
TRANS>
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bool
GroupIntersectionPredicate<PERM,TRANS>::operator()
(
const
PERM &p)
const
{
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return
m_G.sifts(p) && m_H.sifts(p);
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}
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template
<
class
PERM,
class
TRANS>
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bool
GroupIntersectionPredicate<PERM,TRANS>::childRestriction
(
const
PERM &h,
unsigned
int
i,
unsigned
long
beta_i)
const
{
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//TODO: check \beta_l^{g h^{-1}} \in \beta_l^{H_{(beta_1 ... beta_{l-1})}} instead
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// cf. Handbook of Computational Group Theory, sec 4.6.6
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PERM siftee(m_H.n);
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const
unsigned
int
m = m_H.sift(h, siftee, 0, i+1);
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return
i+1 == m;
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}
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template
<
class
PERM,
class
TRANS>
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unsigned
int
GroupIntersectionPredicate<PERM,TRANS>::limit
()
const
{
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return
m_G.B.size();
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}
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}
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#endif // -- GROUPINTERSECTIONPREDICATE_H_
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