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
25 using 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
34 struct 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
43 struct rightshift {
operator ()rightshift44 int operator()(const DATA_TYPE &x, const unsigned offset) const {
45 return float_mem_cast<KEY_TYPE, CAST_TYPE>(x.key) >> offset;
46 }
47 };
48 //] [/float_functor_rightshift]
49
50 //[float_functor_lessthan
51 struct lessthan {
operator ()lessthan52 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
main(int argc,const char ** argv)61 int 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(argv[u]);
70 }
71 std::ifstream input("input.txt", std::ios_base::in | std::ios_base::binary);
72 if (input.fail()) {
73 printf("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(uCount);
86 unsigned v = 0;
87 while (input.good() && v < uCount) {
88 input.read(reinterpret_cast<char *>(&(array[v].key)),
89 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>(array[v].key) & 0x7f800000)) {
92 //Make the top exponent bit high
93 CAST_TYPE temp = 0x40000000 |
94 float_mem_cast<KEY_TYPE, CAST_TYPE>(array[v].key);
95 memcpy(&(array[v].key), &temp, 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(array.begin(), array.end(), lessthan());
111 else
112 float_sort(array.begin(), array.end(), rightshift(), lessthan());
113 end = clock();
114 elapsed = static_cast<double>(end - start) ;
115 std::ofstream ofile;
116 if (stdSort)
117 ofile.open("standard_sort_out.txt", std::ios_base::out |
118 std::ios_base::binary | std::ios_base::trunc);
119 else
120 ofile.open("boost_sort_out.txt", 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(reinterpret_cast<char *>(&(array[v].key)),
125 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("std::sort elapsed time %f\n", total / CLOCKS_PER_SEC);
135 else
136 printf("spreadsort elapsed time %f\n", total / CLOCKS_PER_SEC);
137 return 0;
138 }
139