permlib  0.2.6
Library for permutation computations
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include/permlib/invariant/dade_invariants.h
00001 // ---------------------------------------------------------------------------
00002 //
00003 //  This file is part of PermLib.
00004 //
00005 // Copyright (c) 2009-2011 Thomas Rehn <thomas@carmen76.de>
00006 // All rights reserved.
00007 // 
00008 // Redistribution and use in source and binary forms, with or without
00009 // modification, are permitted provided that the following conditions
00010 // are met:
00011 // 1. Redistributions of source code must retain the above copyright
00012 //    notice, this list of conditions and the following disclaimer.
00013 // 2. Redistributions in binary form must reproduce the above copyright
00014 //    notice, this list of conditions and the following disclaimer in the
00015 //    documentation and/or other materials provided with the distribution.
00016 // 3. The name of the author may not be used to endorse or promote products
00017 //    derived from this software without specific prior written permission.
00018 // 
00019 // THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
00020 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
00021 // OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
00022 // IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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00029 //
00030 // ---------------------------------------------------------------------------
00031 
00032 
00033 #ifndef DADE_INVARIANTS_H_
00034 #define DADE_INVARIANTS_H_
00035 
00036 #include <permlib/transversal/orbit_set.h>
00037 #include <permlib/invariant/linear_form_list.h>
00038 
00039 namespace permlib {
00040 
00042 template<class BSGSIN>
00043 class DadeInvariants {
00044 public:
00045         typedef typename BSGSIN::PERMtype PERM;
00046         typedef typename BSGSIN::TRANStype TRANS;
00047 
00049         DadeInvariants(const BSGSIN& bsgs);
00050 
00052         virtual ~DadeInvariants(){}
00053 
00055 
00059         void invariants(std::list<LinearFormList>& invariantList, unsigned int maximalDegree = 0) const;
00060 private:
00061         const BSGSIN& m_bsgs;
00062 };
00063 
00064 //
00065 // IMPLEMENTATION
00066 //
00067 
00068 
00069 template<class BSGSIN>
00070 DadeInvariants<BSGSIN>::DadeInvariants(const BSGSIN& bsgs) 
00071         : m_bsgs(bsgs)
00072 {  }
00073 
00074 template<class BSGSIN>
00075 void DadeInvariants<BSGSIN>::invariants(std::list<LinearFormList>& invariantList, unsigned int maximalDegree) const
00076 {
00077         const unsigned long n = m_bsgs.n;
00078         
00079         std::map<unsigned long,OrbitSet<PERM,unsigned long> > orbits;
00080         boost::dynamic_bitset<> checked(n);
00081         unsigned long alpha = 0;
00082         while (true) {
00083                 while (checked[alpha] && alpha < n) {
00084                         ++alpha;
00085                 }
00086                 if (alpha >= n)
00087                         break;
00088                 
00089                 OrbitSet<PERM, unsigned long> orbit;
00090                 orbit.orbit(alpha, m_bsgs.S, typename Transversal<PERM>::TrivialAction());
00091                 BOOST_FOREACH(const unsigned long& beta, std::make_pair(orbit.begin(), orbit.end())) {
00092                         checked.set(beta, 1);
00093                 }
00094                 orbits.insert(std::make_pair(alpha, orbit));
00095         }
00096         
00097         typedef std::pair<unsigned long,OrbitSet<PERM,unsigned long> > pair_t;
00098         std::set<unsigned long>::const_iterator setIt;
00099         BOOST_FOREACH(const pair_t& orbit, orbits) {
00100                 unsigned long l = 1;
00101                 while (l < orbit.second.size()) {
00102                         LinearForm form(n);
00103                         setIt = orbit.second.begin();
00104                         for (unsigned int i = 0; i < orbit.second.size()-l; ++i) {
00105                                 form.set(*setIt, 1);
00106                                 ++setIt;
00107                         }
00108                         
00109                         OrbitSet<PERM, LinearForm> formOrbit;
00110                         formOrbit.orbit(form, m_bsgs.S, LinearFormAction<PERM>());
00111                         LinearFormList list;
00112                         BOOST_FOREACH(const LinearForm& lform, std::make_pair(formOrbit.begin(), formOrbit.end())) {
00113                                 list.add(lform);
00114                         }
00115                         
00116                         if (!maximalDegree || list.size() < maximalDegree)
00117                                 invariantList.push_back(list);
00118                         l <<= 1;
00119                 }
00120         }
00121 }
00122 
00123 }
00124 
00125 #endif // -- DADE_INVARIANTS_H_