1// spreadsort float sorting example.
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 <iostream>
20using namespace boost::sort::spreadsort;
21
22#define DATA_TYPE float
23#define CAST_TYPE int
24
25//Pass in an argument to test std::sort
26//Note that this converts NaNs and -0.0 to 0.0, so that sorting results are
27//identical every time
28int main(int argc, const char ** argv) {
29 size_t uCount,uSize=sizeof(DATA_TYPE);
30 bool stdSort = false;
31 unsigned loopCount = 1;
32 for (int u = 1; u < argc; ++u) {
33 if (std::string(argv[u]) == "-std")
34 stdSort = true;
35 else
36 loopCount = atoi(nptr: argv[u]);
37 }
38 std::ifstream input("input.txt", std::ios_base::in | std::ios_base::binary);
39 if (input.fail()) {
40 printf(format: "input.txt could not be opened\n");
41 return 1;
42 }
43 double total = 0.0;
44 std::vector<DATA_TYPE> array;
45 input.seekg (0, std::ios_base::end);
46 size_t length = input.tellg();
47 uCount = length/uSize;
48 //Run multiple loops, if requested
49 for (unsigned u = 0; u < loopCount; ++u) {
50 input.seekg (0, std::ios_base::beg);
51 //Conversion to a vector
52 array.resize(new_size: uCount);
53 unsigned v = 0;
54 while (input.good() && v < uCount) {
55 input.read(s: reinterpret_cast<char *>(&(array[v])), n: uSize );
56 //Checking for denormalized numbers
57 if (!(float_mem_cast<float, int>(data: array[v]) & 0x7f800000)) {
58 //Make the top exponent bit high
59 CAST_TYPE temp = 0x40000000 | float_mem_cast<float, int>(data: array[v]);
60 memcpy(dest: &(array[v]), src: &temp, n: sizeof(DATA_TYPE));
61 }
62 //Testcase doesn't sort NaNs; they just cause confusion
63 if (!(array[v] < 0.0) && !(0.0 < array[v]))
64 array[v] = 0.0;
65 ++v;
66 }
67 clock_t start, end;
68 double elapsed;
69 start = clock();
70 if (stdSort)
71 //std::sort(&(array[0]), &(array[0]) + uCount);
72 std::sort(first: array.begin(), last: array.end());
73 else
74 //boost::sort::spreadsort::spreadsort(&(array[0]), &(array[0]) + uCount);
75 boost::sort::spreadsort::spreadsort(first: array.begin(), last: array.end());
76 end = clock();
77 elapsed = static_cast<double>(end - start) ;
78 std::ofstream ofile;
79 if (stdSort)
80 ofile.open(s: "standard_sort_out.txt", mode: std::ios_base::out |
81 std::ios_base::binary | std::ios_base::trunc);
82 else
83 ofile.open(s: "boost_sort_out.txt", mode: std::ios_base::out |
84 std::ios_base::binary | std::ios_base::trunc);
85 if (ofile.good()) {
86 for (unsigned v = 0; v < array.size(); ++v) {
87 ofile.write(s: reinterpret_cast<char *>(&(array[v])), n: sizeof(array[v]) );
88 }
89 ofile.close();
90 }
91 total += elapsed;
92 array.clear();
93 }
94 input.close();
95 if (stdSort)
96 printf(format: "std::sort elapsed time %f\n", total / CLOCKS_PER_SEC);
97 else
98 printf(format: "spreadsort elapsed time %f\n", total / CLOCKS_PER_SEC);
99 return 0;
100}
101

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