1// a sorting example that uses the worst-case distribution for spreadsort.
2//
3// Copyright Steven Ross 2009-2014.
4//
5// Distributed under the Boost Software License, Version 1.0.
6// (See accompanying file LICENSE_1_0.txt or copy at
7// http://www.boost.org/LICENSE_1_0.txt)
8
9// See http://www.boost.org/libs/sort for library home page.
10
11#include <boost/sort/spreadsort/spreadsort.hpp>
12#include <time.h>
13#include <stdio.h>
14#include <stdlib.h>
15#include <algorithm>
16#include <vector>
17#include <string>
18#include <fstream>
19#include <sstream>
20#include <iostream>
21using namespace boost::sort::spreadsort;
22using namespace std;
23
24#define DATA_TYPE boost::uint64_t
25
26#define ALR_THRESHOLD 3
27
28const unsigned max_count = ALR_THRESHOLD - 1;
29const unsigned bit_shift = detail::rough_log_2_size(input: max_count) -
30 detail::int_log_mean_bin_size;
31const unsigned radix_threshold = detail::rough_log_2_size(input: max_count) + 1;
32
33const DATA_TYPE typed_one = 1;
34
35void
36fill_vector(vector<DATA_TYPE> & input, const DATA_TYPE base_value,
37 unsigned remaining_bits, const vector<unsigned> & indices,
38 int index)
39{
40 if (index < 0) {
41 for (unsigned u = 0; u < max_count; ++u)
42 input.push_back(x: (base_value << remaining_bits) +
43 (rand() % (1 << remaining_bits)));
44 }
45 else {
46 unsigned shift = indices[index];
47 fill_vector(input, base_value: (base_value << shift) + ((1 << shift) - 1),
48 remaining_bits: remaining_bits - shift, indices, index: index - 1);
49 fill_vector(input, base_value: base_value << shift, remaining_bits: remaining_bits - shift, indices,
50 index: index - 1);
51 }
52}
53
54//Generates a random index from 0 up to but not including count.
55unsigned
56get_index(unsigned count)
57{
58 unsigned result = unsigned((rand() % (1 << 16))*uint64_t(count)/(1 << 16));
59 if (result >= count)
60 return count - 1;
61 return result;
62}
63
64//Tests std::sort vs boost::sort::spreadsort on boost::sort's worst distribution.
65int main(int, const char **) {
66 unsigned total_length = sizeof(DATA_TYPE) * 8;
67 double std_sort_time = 0;
68 double spreadsort_time = 0;
69 for (int repetition = 0; repetition < 10; ++repetition) {
70 vector<DATA_TYPE> input;
71 vector<unsigned> offsets;
72 unsigned bit_length = total_length - radix_threshold;
73 unsigned bit_offset = bit_shift;
74 for (; bit_length >= ++bit_offset; bit_length -= bit_offset)
75 offsets.push_back(x: bit_offset);
76 for (int ii = (1 << bit_length) - 1; ii >= 0; --ii)
77 fill_vector(input, base_value: ii, remaining_bits: total_length - bit_length,
78 indices: offsets, index: offsets.size() - 1);
79
80 //Randomize the inputs slightly so they aren't in reverse-sorted order, for
81 //which std::sort is very fast.
82 for (unsigned u = 0; u < input.size() / 10; ++u)
83 std::swap(a&: input[get_index(count: input.size())], b&: input[get_index(count: input.size())]);
84
85 //Run both std::sort and boost::sort::spreadsort.
86 for (unsigned u = 0; u < 2; ++u) {
87 vector<DATA_TYPE> array = input;
88 clock_t start, end;
89 double elapsed;
90 start = clock();
91 if (u)
92 std::sort(first: array.begin(), last: array.end());
93 else
94 boost::sort::spreadsort::spreadsort(first: array.begin(), last: array.end());
95 end = clock();
96 elapsed = static_cast<double>(end - start);
97 if (u)
98 std_sort_time += elapsed / CLOCKS_PER_SEC;
99 else
100 spreadsort_time += elapsed / CLOCKS_PER_SEC;
101 array.clear();
102 }
103 }
104
105 printf(format: "std::sort elapsed time %f\n", std_sort_time);
106 printf(format: "spreadsort elapsed time %f\n", spreadsort_time);
107 return 0;
108}
109

source code of boost/libs/sort/example/binaryalrbreaker.cpp