139 lines
4.1 KiB
C++
139 lines
4.1 KiB
C++
// spreadsort float functor sorting example.
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//
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// Copyright Steven Ross 2009.
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// See http://www.boost.org/libs/sort for library home page.
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// Caution: this file contains Quickbook markup as well as code
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// and comments, don't change any of the special comment markups!
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#include <boost/sort/spreadsort/spreadsort.hpp>
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#include <time.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <algorithm>
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#include <vector>
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#include <string>
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#include <fstream>
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#include <sstream>
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#include <iostream>
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using namespace boost::sort::spreadsort;
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//[float_functor_types
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#define CAST_TYPE int
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#define KEY_TYPE float
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//] [/float_functor_types]
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//[float_functor_datatypes
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struct DATA_TYPE {
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KEY_TYPE key;
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std::string data;
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};
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//] [/float_functor_datatypes]
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//[float_functor_rightshift
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// Casting to an integer before bitshifting
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struct rightshift {
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int operator()(const DATA_TYPE &x, const unsigned offset) const {
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return float_mem_cast<KEY_TYPE, CAST_TYPE>(x.key) >> offset;
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}
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};
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//] [/float_functor_rightshift]
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//[float_functor_lessthan
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struct lessthan {
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bool operator()(const DATA_TYPE &x, const DATA_TYPE &y) const {
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return x.key < y.key;
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}
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};
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//] [/float_functor_lessthan]
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// Pass in an argument to test std::sort
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// Note that this converts NaNs and -0.0 to 0.0, so that sorting results are
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// identical every time
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int main(int argc, const char ** argv) {
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size_t uCount,uSize=sizeof(DATA_TYPE);
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bool stdSort = false;
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unsigned loopCount = 1;
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for (int u = 1; u < argc; ++u) {
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if (std::string(argv[u]) == "-std")
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stdSort = true;
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else
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loopCount = atoi(argv[u]);
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}
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std::ifstream input("input.txt", std::ios_base::in | std::ios_base::binary);
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if (input.fail()) {
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printf("input.txt could not be opened\n");
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return 1;
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}
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double total = 0.0;
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std::vector<DATA_TYPE> array;
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input.seekg (0, std::ios_base::end);
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size_t length = input.tellg();
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uCount = length/uSize;
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//Run multiple loops, if requested
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for (unsigned u = 0; u < loopCount; ++u) {
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input.seekg (0, std::ios_base::beg);
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//Conversion to a vector
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array.resize(uCount);
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unsigned v = 0;
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while (input.good() && v < uCount) {
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input.read(reinterpret_cast<char *>(&(array[v].key)),
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sizeof(array[v].key));
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//Checking for denormalized numbers; float_sort looks too fast on them.
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if (!(float_mem_cast<KEY_TYPE, CAST_TYPE>(array[v].key) & 0x7f800000)) {
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//Make the top exponent bit high
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CAST_TYPE temp = 0x40000000 |
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float_mem_cast<KEY_TYPE, CAST_TYPE>(array[v].key);
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memcpy(&(array[v].key), &temp, sizeof(KEY_TYPE));
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}
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//Testcase doesn't sort NaNs; they just cause confusion
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if (!(array[v].key < 0.0) && !(0.0 < array[v].key))
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array[v].key = 0.0;
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//Adding the data, in this case a string
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std::stringstream intstr;
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intstr << array[v].key;
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array[v].data = intstr.str();
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++v;
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}
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clock_t start, end;
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double elapsed;
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start = clock();
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if (stdSort)
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std::sort(array.begin(), array.end(), lessthan());
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else
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float_sort(array.begin(), array.end(), rightshift(), lessthan());
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end = clock();
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elapsed = static_cast<double>(end - start) ;
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std::ofstream ofile;
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if (stdSort)
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ofile.open("standard_sort_out.txt", std::ios_base::out |
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std::ios_base::binary | std::ios_base::trunc);
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else
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ofile.open("boost_sort_out.txt", std::ios_base::out |
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std::ios_base::binary | std::ios_base::trunc);
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if (ofile.good()) {
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for (unsigned v = 0; v < array.size(); ++v) {
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ofile.write(reinterpret_cast<char *>(&(array[v].key)),
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sizeof(array[v].key));
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ofile << array[v].data;
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}
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ofile.close();
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}
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total += elapsed;
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array.clear();
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}
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if (stdSort)
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printf("std::sort elapsed time %f\n", total / CLOCKS_PER_SEC);
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else
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printf("spreadsort elapsed time %f\n", total / CLOCKS_PER_SEC);
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return 0;
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}
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