33#ifndef SCHREIERGENERATOR_H_
34#define SCHREIERGENERATOR_H_
36#include <permlib/common.h>
37#include <permlib/generator/generator.h>
40#include <boost/scoped_ptr.hpp>
41#include <boost/tuple/tuple.hpp>
42#include <boost/next_prior.hpp>
54template <
class PERM,
class TRANS>
58 typedef typename std::list<typename PERM::ptr>::const_iterator
PERMlistIt;
60 typedef typename std::list<unsigned long>::const_iterator
TRANSlistIt;
88 void update(
unsigned int j);
98 unsigned int m_posSlimit;
100 unsigned int m_posUlimit;
103 unsigned long m_beta;
105 std::stack<boost::tuple<unsigned int, unsigned int, unsigned int, unsigned int> > m_stackTodo;
119template <
class PERM,
class TRANS>
121 : m_Sbegin(S_begin), m_Scurrent(S_begin), m_Send(S_end),
122 m_U(U), m_Ubegin(m_U->begin()), m_Ucurrent(m_U->begin()), m_Uend(m_U->end()),
123 m_posS(0), m_posSlimit(0), m_posU(0), m_posUlimit(0), m_u_beta(0)
128template <
class PERM,
class TRANS>
133template <
class PERM,
class TRANS>
134void SchreierGenerator<PERM, TRANS>::init() {
135 m_beta = *m_Ucurrent;
137 m_u_beta = m_U->at(m_beta);
141template <
class PERM,
class TRANS>
143 if (m_Send != m_Scurrent && m_Uend != m_Ucurrent && (!m_posUlimit || m_posU < m_posUlimit)) {
144 const PERM &x = **m_Scurrent;
145 if (m_U->trivialByDefinition(x, x / m_beta)) {
152 if (!m_stackTodo.empty()) {
153 boost::tuple<unsigned int, unsigned int, unsigned int, unsigned int> lastTuple = m_stackTodo.top();
156 m_posS = boost::get<0>(lastTuple);
157 m_posSlimit = boost::get<1>(lastTuple);
158 m_posU = boost::get<2>(lastTuple);
159 m_posUlimit = boost::get<3>(lastTuple);
167template <
class PERM,
class TRANS>
171 if (m_Scurrent == m_Send) {
172 m_Scurrent = boost::next(m_Sbegin, m_posSlimit);
173 m_posS = m_posSlimit;
176 if (m_Ucurrent != m_Uend)
184template <
class PERM,
class TRANS>
186 BOOST_ASSERT(m_Scurrent != m_Send);
187 BOOST_ASSERT(m_Ucurrent != m_Uend);
189 PERMLIB_DEBUG(std::cout <<
"s = " << m_posS <<
"; u = " << m_posU << std::endl;)
190 const PERM &x = **m_Scurrent;
192 PERM g = *m_u_beta * x;
193 boost::scoped_ptr<PERM> u_beta_ptr2(m_U->at(x / m_beta));
194 u_beta_ptr2->invertInplace();
202template <
class PERM,
class TRANS>
204 m_Scurrent = m_Sbegin;
205 m_Ucurrent = m_Ubegin;
207 while (--i>=0) ++m_Scurrent;
209 while (--i>=0) ++m_Ucurrent;
211 if (m_Ucurrent != m_Uend)
215template <
class PERM,
class TRANS>
217 if (U == m_U && S_begin == m_Sbegin && S_end == m_Send)
222 m_Ubegin = U->begin();
227template <
class PERM,
class TRANS>
229 m_stackTodo.push(boost::make_tuple(m_posS, m_posSlimit, m_posU, m_posUlimit));
230 m_posUlimit = m_posU;
interface for group element generators
Definition: generator.h:40
stateful generator of Schreier generators
Definition: schreier_generator.h:55
PERM next()
generates an element
Definition: schreier_generator.h:185
bool hasNext()
true, iff more elements can be generated
Definition: schreier_generator.h:142
void update(TRANS *U, PERMlistIt S_begin, PERMlistIt S_end)
updates transversal and group generators that the Schreier generators are constructed from
Definition: schreier_generator.h:216
std::list< typenamePERM::ptr >::const_iterator PERMlistIt
const iterator to a list of PERMutations
Definition: schreier_generator.h:58
SchreierGenerator(const TRANS *U, PERMlistIt S_begin, PERMlistIt S_end)
constructor
Definition: schreier_generator.h:120
std::list< unsignedlong >::const_iterator TRANSlistIt
const iterator to a list of points (unsigned long)
Definition: schreier_generator.h:60