ceph/src/boost/libs/sort/example/shiftfloatsample.cpp

   1 // float_sort rightshift functor 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>
  20 using namespace boost::sort::spreadsort;
  21
  22 #define DATA_TYPE float
  23 #define CAST_TYPE int
  24
  25 //Casting to an integer before bitshifting
  26 struct rightshift {
  27   inline int operator()(const DATA_TYPE &x, const unsigned offset) const {
  28     return float_mem_cast<DATA_TYPE, int>(x) >> offset;
  29   }
  30 };
  31
  32
  33 //Pass in an argument to test std::sort
  34 //Note that this converts NaNs and -0.0 to 0.0, so that sorting results are
  35 //identical every time
  36 int main(int argc, const char ** argv) {
  37   size_t uCount,uSize=sizeof(DATA_TYPE);
  38   bool stdSort = false;
  39   unsigned loopCount = 1;
  40   for (int u = 1; u < argc; ++u) {
  41     if (std::string(argv[u]) == "-std")
  42       stdSort = true;
  43     else
  44       loopCount = atoi(argv[u]);
  45   }
  46   std::ifstream input("input.txt", std::ios_base::in | std::ios_base::binary);
  47   if (input.fail()) {
  48     printf("input.txt could not be opened\n");
  49     return 1;
  50   }
  51   double total = 0.0;
  52   std::vector<DATA_TYPE> array;
  53   input.seekg (0, std::ios_base::end);
  54     size_t length = input.tellg();
  55   uCount = length/uSize;
  56   //Run multiple loops, if requested
  57   for (unsigned u = 0; u < loopCount; ++u) {
  58     input.seekg (0, std::ios_base::beg);
  59     //Conversion to a vector
  60     array.resize(uCount);
  61     unsigned v = 0;
  62     while (input.good() && v < uCount) {
  63       input.read(reinterpret_cast<char *>(&(array[v])), uSize );
  64      //Testcase doesn't sort NaNs; they just cause confusion
  65      if (!(array[v] < 0.0) && !(0.0 < array[v]))
  66       array[v] = 0.0;
  67      //Checking for denormalized numbers
  68      if (!(float_mem_cast<float, int>(array[v]) & 0x7f800000)) {
  69        //Make the top exponent bit high
  70        CAST_TYPE temp = 0x40000000 | float_mem_cast<float, int>(array[v]);
  71        memcpy(&(array[v]), &temp, sizeof(DATA_TYPE));
  72      }
  73      ++v;
  74     }
  75     clock_t start, end;
  76     double elapsed;
  77     start = clock();
  78     if (stdSort)
  79       //std::sort(&(array[0]), &(array[0]) + uCount);
  80       std::sort(array.begin(), array.end());
  81     else
  82       //float_sort(&(array[0]), &(array[0]) + uCount, rightshift());
  83       float_sort(array.begin(), array.end(), rightshift());
  84     end = clock();
  85     elapsed = static_cast<double>(end - start) ;
  86     std::ofstream ofile;
  87     if (stdSort)
  88       ofile.open("standard_sort_out.txt", std::ios_base::out |
  89                  std::ios_base::binary | std::ios_base::trunc);
  90     else
  91       ofile.open("boost_sort_out.txt", std::ios_base::out |
  92                  std::ios_base::binary | std::ios_base::trunc);
  93     if (ofile.good()) {
  94       for (unsigned v = 0; v < array.size(); ++v) {
  95         ofile.write(reinterpret_cast<char *>(&(array[v])), sizeof(array[v]) );
  96       }
  97       ofile.close();
  98     }
  99     total += elapsed;
 100     array.clear();
 101   }
 102   if (stdSort)
 103     printf("std::sort elapsed time %f\n", total / CLOCKS_PER_SEC);
 104   else
 105     printf("spreadsort elapsed time %f\n", total / CLOCKS_PER_SEC);
 106   return 0;
 107 }