PermLib

product_replacement_generator.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,
00023 // INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
00024 // NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
00025 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
00026 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
00027 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
00028 // THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00029 //
00030 // ---------------------------------------------------------------------------
00031 
00032 
00033 #ifndef PRODUCTREPLACEMENTGENERATOR_H
00034 #define PRODUCTREPLACEMENTGENERATOR_H
00035 
00036 #include <permlib/generator/random_generator.h>
00037 
00038 #include <vector>
00039 #include <boost/iterator/indirect_iterator.hpp>
00040 
00041 namespace permlib {
00042 
00044 template <class PERM>
00045 class ProductReplacementGenerator : public RandomGenerator<PERM> {
00046 public:
00048 
00052         template <class InputIterator>
00053         ProductReplacementGenerator(InputIterator generatorsBegin, InputIterator generatorsEnd);
00054         
00055         virtual PERM next();
00056 private:
00057         std::vector<PERM> m_generators;
00058 };
00059 
00060 //
00061 //     ----       IMPLEMENTATION
00062 //
00063 
00064 template <class PERM>
00065 template <class InputIterator>
00066 ProductReplacementGenerator<PERM>::ProductReplacementGenerator(InputIterator generatorsBegin, InputIterator generatorsEnd) 
00067         : m_generators(boost::indirect_iterator<InputIterator, PERM>(generatorsBegin), 
00068                                    boost::indirect_iterator<InputIterator, PERM>(generatorsEnd)) 
00069 {
00070         const unsigned int additionalElements = 10;
00071         const unsigned int oldSize = m_generators.size();
00072         const unsigned int replacementRounds = std::max(oldSize * 10, static_cast<unsigned int>(100));
00073         
00074         m_generators.reserve(oldSize + additionalElements + 1);
00075         for (unsigned int i = 0; i < additionalElements; ++i) {
00076                 m_generators.push_back(m_generators[randomInt(oldSize)]);
00077         }
00078         m_generators.push_back(PERM(m_generators[0].size()));
00079         
00080         for (unsigned int k = 0; k < replacementRounds; ++k) {
00081                 next();
00082         }
00083 }
00084 
00085 template <class PERM>
00086 PERM ProductReplacementGenerator<PERM>::next() {
00087         unsigned int i = randomInt(m_generators.size() - 1);
00088         unsigned int j = randomInt(m_generators.size() - 2);
00089         if (j >= i) ++j;
00090         switch (randomInt(4)) {
00091         case 0:
00092                 m_generators[i] *=  m_generators[j]; break;
00093         case 1:
00094                 m_generators[i] *= ~m_generators[j]; break;
00095         case 2:
00096                 m_generators[i] ^=  m_generators[j]; break;
00097         case 3:
00098                 m_generators[i] ^= ~m_generators[j]; break;
00099         }
00100         m_generators[m_generators.size()-1] *= m_generators[i];
00101         return m_generators[m_generators.size()-1];
00102 }
00103 
00104 }
00105 
00106 #endif // -- PRODUCTREPLACEMENTGENERATOR_H