1// spreadsort float functor sorting example.
2//
3// Copyright Steven Ross 2009.
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// Caution: this file contains Quickbook markup as well as code
12// and comments, don't change any of the special comment markups!
13
14#include <boost/sort/spreadsort/spreadsort.hpp>
15#include <time.h>
16#include <stdio.h>
17#include <stdlib.h>
18#include <algorithm>
19#include <vector>
20#include <string>
21#include <fstream>
22#include <sstream>
23#include <iostream>
24
25using namespace boost::sort::spreadsort;
26
27//[float_functor_types
28#define CAST_TYPE int
29#define KEY_TYPE float
30//] [/float_functor_types]
31
32
33//[float_functor_datatypes
34struct DATA_TYPE {
35 KEY_TYPE key;
36 std::string data;
37};
38//] [/float_functor_datatypes]
39
40
41//[float_functor_rightshift
42// Casting to an integer before bitshifting
43struct rightshift {
44 int operator()(const DATA_TYPE &x, const unsigned offset) const {
45 return float_mem_cast<KEY_TYPE, CAST_TYPE>(data: x.key) >> offset;
46 }
47};
48//] [/float_functor_rightshift]
49
50//[float_functor_lessthan
51struct lessthan {
52 bool operator()(const DATA_TYPE &x, const DATA_TYPE &y) const {
53 return x.key < y.key;
54 }
55};
56//] [/float_functor_lessthan]
57
58// Pass in an argument to test std::sort
59// Note that this converts NaNs and -0.0 to 0.0, so that sorting results are
60// identical every time
61int main(int argc, const char ** argv) {
62 size_t uCount,uSize=sizeof(DATA_TYPE);
63 bool stdSort = false;
64 unsigned loopCount = 1;
65 for (int u = 1; u < argc; ++u) {
66 if (std::string(argv[u]) == "-std")
67 stdSort = true;
68 else
69 loopCount = atoi(nptr: argv[u]);
70 }
71 std::ifstream input("input.txt", std::ios_base::in | std::ios_base::binary);
72 if (input.fail()) {
73 printf(format: "input.txt could not be opened\n");
74 return 1;
75 }
76 double total = 0.0;
77 std::vector<DATA_TYPE> array;
78 input.seekg (0, std::ios_base::end);
79 size_t length = input.tellg();
80 uCount = length/uSize;
81 //Run multiple loops, if requested
82 for (unsigned u = 0; u < loopCount; ++u) {
83 input.seekg (0, std::ios_base::beg);
84 //Conversion to a vector
85 array.resize(new_size: uCount);
86 unsigned v = 0;
87 while (input.good() && v < uCount) {
88 input.read(s: reinterpret_cast<char *>(&(array[v].key)),
89 n: sizeof(array[v].key));
90 //Checking for denormalized numbers; float_sort looks too fast on them.
91 if (!(float_mem_cast<KEY_TYPE, CAST_TYPE>(data: array[v].key) & 0x7f800000)) {
92 //Make the top exponent bit high
93 CAST_TYPE temp = 0x40000000 |
94 float_mem_cast<KEY_TYPE, CAST_TYPE>(data: array[v].key);
95 memcpy(dest: &(array[v].key), src: &temp, n: sizeof(KEY_TYPE));
96 }
97 //Testcase doesn't sort NaNs; they just cause confusion
98 if (!(array[v].key < 0.0) && !(0.0 < array[v].key))
99 array[v].key = 0.0;
100 //Adding the data, in this case a string
101 std::stringstream intstr;
102 intstr << array[v].key;
103 array[v].data = intstr.str();
104 ++v;
105 }
106 clock_t start, end;
107 double elapsed;
108 start = clock();
109 if (stdSort)
110 std::sort(first: array.begin(), last: array.end(), comp: lessthan());
111 else
112 float_sort(first: array.begin(), last: array.end(), rshift: rightshift(), comp: lessthan());
113 end = clock();
114 elapsed = static_cast<double>(end - start) ;
115 std::ofstream ofile;
116 if (stdSort)
117 ofile.open(s: "standard_sort_out.txt", mode: std::ios_base::out |
118 std::ios_base::binary | std::ios_base::trunc);
119 else
120 ofile.open(s: "boost_sort_out.txt", mode: std::ios_base::out |
121 std::ios_base::binary | std::ios_base::trunc);
122 if (ofile.good()) {
123 for (unsigned v = 0; v < array.size(); ++v) {
124 ofile.write(s: reinterpret_cast<char *>(&(array[v].key)),
125 n: sizeof(array[v].key));
126 ofile << array[v].data;
127 }
128 ofile.close();
129 }
130 total += elapsed;
131 array.clear();
132 }
133 if (stdSort)
134 printf(format: "std::sort elapsed time %f\n", total / CLOCKS_PER_SEC);
135 else
136 printf(format: "spreadsort elapsed time %f\n", total / CLOCKS_PER_SEC);
137 return 0;
138}
139

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