permlib  0.2.9
Library for permutation computations
random_schreier_generator.h
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31 
32 
33 #ifndef RANDOMSCHREIERGENERATOR_H_
34 #define RANDOMSCHREIERGENERATOR_H_
35 
36 #include <permlib/generator/random_generator.h>
37 
38 namespace permlib {
39 
41 
45 template <class PERM,class TRANS>
47 public:
49 
54  RandomSchreierGenerator(const BSGS<PERM,TRANS> &bsgs, unsigned int i, const TRANS &U);
55  virtual PERM next();
56 private:
57  const BSGS<PERM,TRANS> &m_bsgs;
58  unsigned int m_i;
59  const TRANS &m_U;
60 };
61 
62 //
63 // ---- IMPLEMENTATION
64 //
65 
66 template <class PERM,class TRANS>
68  : m_bsgs(bsgs), m_i(i), m_U(U)
69 { }
70 
71 template <class PERM,class TRANS>
73  PERM g = m_bsgs.random(m_i);
74  boost::scoped_ptr<PERM> u_g(m_U.at(g / m_bsgs.B[m_i]));
75  u_g->invertInplace();
76  g *= *u_g;
77  return g;
78 }
79 
80 }
81 
82 #endif // -- RANDOMSCHREIERGENERATOR_H_
abstract base class for random group element generators
Definition: random_generator.h:42
RandomSchreierGenerator(const BSGS< PERM, TRANS > &bsgs, unsigned int i, const TRANS &U)
constructor
Definition: random_schreier_generator.h:67
virtual PERM next()
generates an element
Definition: random_schreier_generator.h:72
generates a uniformly distributed random element of
Definition: random_schreier_generator.h:46
Represents a base and strong generating set (BSGS)
Definition: bsgs.h:58
Definition: abstract_bsgs.h:49