// a sorting example that uses the worst-case distribution for spreadsort. // // Copyright Steven Ross 2009-2014. // // Distributed under the Boost Software License, Version 1.0. // (See accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) // See http://www.boost.org/libs/sort for library home page. #include #include #include #include #include #include #include #include #include #include using namespace boost::sort::spreadsort; using namespace std; #define DATA_TYPE boost::uint64_t #define ALR_THRESHOLD 3 const unsigned max_count = ALR_THRESHOLD - 1; const unsigned bit_shift = detail::rough_log_2_size(max_count) - detail::int_log_mean_bin_size; const unsigned radix_threshold = detail::rough_log_2_size(max_count) + 1; const DATA_TYPE typed_one = 1; void fill_vector(vector & input, const DATA_TYPE base_value, unsigned remaining_bits, const vector & indices, int index) { if (index < 0) { for (unsigned u = 0; u < max_count; ++u) input.push_back((base_value << remaining_bits) + (rand() % (1 << remaining_bits))); } else { unsigned shift = indices[index]; fill_vector(input, (base_value << shift) + ((1 << shift) - 1), remaining_bits - shift, indices, index - 1); fill_vector(input, base_value << shift, remaining_bits - shift, indices, index - 1); } } //Generates a random index from 0 up to but not including count. unsigned get_index(unsigned count) { unsigned result = unsigned((rand() % (1 << 16))*uint64_t(count)/(1 << 16)); if (result >= count) return count - 1; return result; } //Tests std::sort vs boost::sort::spreadsort on boost::sort's worst distribution. int main(int, const char **) { unsigned total_length = sizeof(DATA_TYPE) * 8; double std_sort_time = 0; double spreadsort_time = 0; for (int repetition = 0; repetition < 10; ++repetition) { vector input; vector offsets; unsigned bit_length = total_length - radix_threshold; unsigned bit_offset = bit_shift; for (; bit_length >= ++bit_offset; bit_length -= bit_offset) offsets.push_back(bit_offset); for (int ii = (1 << bit_length) - 1; ii >= 0; --ii) fill_vector(input, ii, total_length - bit_length, offsets, offsets.size() - 1); //Randomize the inputs slightly so they aren't in reverse-sorted order, for //which std::sort is very fast. for (unsigned u = 0; u < input.size() / 10; ++u) std::swap(input[get_index(input.size())], input[get_index(input.size())]); //Run both std::sort and boost::sort::spreadsort. for (unsigned u = 0; u < 2; ++u) { vector array = input; clock_t start, end; double elapsed; start = clock(); if (u) std::sort(array.begin(), array.end()); else boost::sort::spreadsort::spreadsort(array.begin(), array.end()); end = clock(); elapsed = static_cast(end - start); if (u) std_sort_time += elapsed / CLOCKS_PER_SEC; else spreadsort_time += elapsed / CLOCKS_PER_SEC; array.clear(); } } printf("std::sort elapsed time %f\n", std_sort_time); printf("spreadsort elapsed time %f\n", spreadsort_time); return 0; }