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