text: //---------------------------------------------------------------------------//
  // Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@gmail.com>
  //
  // Distributed under the Boost Software License, Version 1.0
  // See accompanying file LICENSE_1_0.txt or copy at
  // http://www.boost.org/LICENSE_1_0.txt
  //
  // See http://kylelutz.github.com/compute for more information.
  //---------------------------------------------------------------------------//
  
  #include <iostream>
  
  #include <boost/compute/function.hpp>
  #include <boost/compute/system.hpp>
  #include <boost/compute/algorithm/count_if.hpp>
  #include <boost/compute/container/vector.hpp>
  #include <boost/compute/iterator/buffer_iterator.hpp>
  #include <boost/compute/random/default_random_engine.hpp>
  #include <boost/compute/types/builtin.hpp>
  
  namespace compute = boost::compute;
  
  int main()
  {
      // get default device and setup context
      compute::device gpu = compute::system::default_device();
      compute::context context(gpu);
      compute::command_queue queue(context, gpu);
  
      std::cout << "device: " << gpu.name() << std::endl;
  
      using compute::uint_;
      using compute::uint2_;
  
      // ten million random points
      size_t n = 10000000;
  
      // generate random numbers
      compute::default_random_engine rng(queue);
      compute::vector<uint_> vector(n * 2, context);
      rng.generate(vector.begin(), vector.end(), queue);
  
      // function returing true if the point is within the unit circle
      BOOST_COMPUTE_FUNCTION(bool, is_in_unit_circle, (const uint2_ point),
      {
          const float x = point.x / (float) UINT_MAX - 1;
          const float y = point.y / (float) UINT_MAX - 1;
  
          return (x*x + y*y) < 1.0f;
      });
  
      // iterate over vector<uint> as vector<uint2>
      compute::buffer_iterator<uint2_> start =
          compute::make_buffer_iterator<uint2_>(vector.get_buffer(), 0);
      compute::buffer_iterator<uint2_> end =
          compute::make_buffer_iterator<uint2_>(vector.get_buffer(), vector.size() / 2);
  
      // count number of random points within the unit circle
      size_t count = compute::count_if(start, end, is_in_unit_circle, queue);
  
      // print out values
      float count_f = static_cast<float>(count);
      std::cout << "count: " << count << " / " << n << std::endl;
      std::cout << "ratio: " << count_f / float(n) << std::endl;
      std::cout << "pi = " << (count_f / float(n)) * 4.0f << std::endl;
  
      return 0;
  }
  