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- // 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 <boost/sort/spreadsort/spreadsort.hpp>
- #include <time.h>
- #include <stdio.h>
- #include <stdlib.h>
- #include <algorithm>
- #include <vector>
- #include <string>
- #include <fstream>
- #include <sstream>
- #include <iostream>
- 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<DATA_TYPE> & input, const DATA_TYPE base_value,
- unsigned remaining_bits, const vector<unsigned> & 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<DATA_TYPE> input;
- vector<unsigned> 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<DATA_TYPE> 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<double>(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;
- }
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