ceph/src/boost/libs/compute/example/longest_vector.cpp

   1 //---------------------------------------------------------------------------//
   2 // Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@gmail.com>
   3 //
   4 // Distributed under the Boost Software License, Version 1.0
   5 // See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt
   7 //
   8 // See http://boostorg.github.com/compute for more information.
   9 //---------------------------------------------------------------------------//
  10
  11 #include <iostream>
  12 #include <iterator>
  13
  14 #include <boost/compute/algorithm/max_element.hpp>
  15 #include <boost/compute/container/vector.hpp>
  16 #include <boost/compute/functional/geometry.hpp>
  17 #include <boost/compute/iterator/transform_iterator.hpp>
  18 #include <boost/compute/types/fundamental.hpp>
  19
  20 namespace compute = boost::compute;
  21
  22 // this example shows how to use the max_element() algorithm along with
  23 // a transform_iterator and the length() function to find the longest
  24 // 4-component vector in an array of vectors
  25 int main()
  26 {
  27     using compute::float4_;
  28
  29     // vectors data
  30     float data[] = { 1.0f, 2.0f, 3.0f, 0.0f,
  31                      4.0f, 5.0f, 6.0f, 0.0f,
  32                      7.0f, 8.0f, 9.0f, 0.0f,
  33                      0.0f, 0.0f, 0.0f, 0.0f };
  34
  35     // create device vector with the vector data
  36     compute::vector<float4_> vector(
  37         reinterpret_cast<float4_ *>(data),
  38         reinterpret_cast<float4_ *>(data) + 4
  39     );
  40
  41     // find the longest vector
  42     compute::vector<float4_>::const_iterator iter =
  43         compute::max_element(
  44             compute::make_transform_iterator(
  45                 vector.begin(), compute::length<float4_>()
  46             ),
  47             compute::make_transform_iterator(
  48                 vector.end(), compute::length<float4_>()
  49             )
  50         ).base();
  51
  52     // print the index of the longest vector
  53     std::cout << "longest vector index: "
  54               << std::distance(vector.begin(), iter)
  55               << std::endl;
  56
  57     return 0;
  58 }