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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
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 uint additionalElements = 10;
00071 const uint oldSize = m_generators.size();
00072 const uint replacementRounds = std::max(oldSize * 10, static_cast<uint>(100));
00073
00074 m_generators.reserve(oldSize + additionalElements + 1);
00075 for (uint 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 (uint k = 0; k < replacementRounds; ++k) {
00081 next();
00082 }
00083 }
00084
00085 template <class PERM>
00086 PERM ProductReplacementGenerator<PERM>::next() {
00087 uint i = randomInt(m_generators.size() - 1);
00088 uint 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