// 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; | |
} |