ceph/src/boost/libs/compute/include/boost/compute/functional/popcount.hpp

   1 //---------------------------------------------------------------------------//
   2 // Copyright (c) 2013-2014 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 #ifndef BOOST_COMPUTE_FUNCTIONAL_POPCOUNT_HPP
  12 #define BOOST_COMPUTE_FUNCTIONAL_POPCOUNT_HPP
  13
  14 #include <boost/compute/function.hpp>
  15 #include <boost/compute/type_traits/type_name.hpp>
  16
  17 namespace boost {
  18 namespace compute {
  19
  20 /// Returns the number of non-zero bits in \p x.
  21 ///
  22 /// \see_opencl_ref{popcount}
  23 template<class T>
  24 class popcount : public function<T(T)>
  25 {
  26 public:
  27     popcount()
  28         : function<T(T)>("boost_popcount")
  29     {
  30         std::stringstream s;
  31         s << "inline " << type_name<T>() << " boost_popcount"
  32           << "(const " << type_name<T>() << " x)\n"
  33           << "{\n"
  34           // use built-in popcount if opencl 1.2 is supported
  35           << "#if __OPENCL_VERSION__ >= 120\n"
  36           << "    return popcount(x);\n"
  37           // fallback to generic popcount() implementation
  38           << "#else\n"
  39           << "    " << type_name<T>() << " count = 0;\n"
  40           << "    for(" << type_name<T>() << " i = 0; i < sizeof(i) * CHAR_BIT; i++){\n"
  41           << "        if(x & (" << type_name<T>() << ") 1 << i){\n"
  42           << "            count++;\n"
  43           << "        }\n"
  44           << "    }\n"
  45           << "    return count;\n"
  46           << "#endif\n"
  47           << "}\n";
  48         this->set_source(s.str());
  49     }
  50 };
  51
  52 } // end compute namespace
  53 } // end boost namespace
  54
  55 #endif // BOOST_COMPUTE_FUNCTIONAL_POPCOUNT_HPP