ceph/src/boost/boost/compute/algorithm/exclusive_scan.hpp

   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 #ifndef BOOST_COMPUTE_ALGORITHM_EXCLUSIVE_SCAN_HPP
  12 #define BOOST_COMPUTE_ALGORITHM_EXCLUSIVE_SCAN_HPP
  13
  14 #include <boost/compute/functional.hpp>
  15 #include <boost/compute/system.hpp>
  16 #include <boost/compute/command_queue.hpp>
  17 #include <boost/compute/algorithm/detail/scan.hpp>
  18
  19 namespace boost {
  20 namespace compute {
  21
  22 /// Performs an exclusive scan of the elements in the range [\p first, \p last)
  23 /// and stores the results in the range beginning at \p result.
  24 ///
  25 /// Each element in the output is assigned to the sum of all the previous
  26 /// values in the input.
  27 ///
  28 /// \param first first element in the range to scan
  29 /// \param last last element in the range to scan
  30 /// \param result first element in the result range
  31 /// \param init value used to initialize the scan sequence
  32 /// \param binary_op associative binary operator
  33 /// \param queue command queue to perform the operation
  34 ///
  35 /// \return \c OutputIterator to the end of the result range
  36 ///
  37 /// The default operation is to add the elements up.
  38 ///
  39 /// \snippet test/test_scan.cpp exclusive_scan_int
  40 ///
  41 /// But different associative operation can be specified as \p binary_op
  42 /// instead (e.g., multiplication, maximum, minimum). Also value used to
  43 /// initialized the scan sequence can be specified.
  44 ///
  45 /// \snippet test/test_scan.cpp exclusive_scan_int_multiplies
  46 ///
  47 /// Space complexity on GPUs: \Omega(n)<br>
  48 /// Space complexity on GPUs when \p first == \p result: \Omega(2n)<br>
  49 /// Space complexity on CPUs: \Omega(1)
  50 ///
  51 /// \see inclusive_scan()
  52 template<class InputIterator, class OutputIterator, class T, class BinaryOperator>
  53 inline OutputIterator
  54 exclusive_scan(InputIterator first,
  55                InputIterator last,
  56                OutputIterator result,
  57                T init,
  58                BinaryOperator binary_op,
  59                command_queue &queue = system::default_queue())
  60 {
  61     return detail::scan(first, last, result, true, init, binary_op, queue);
  62 }
  63
  64 /// \overload
  65 template<class InputIterator, class OutputIterator, class T>
  66 inline OutputIterator
  67 exclusive_scan(InputIterator first,
  68                InputIterator last,
  69                OutputIterator result,
  70                T init,
  71                command_queue &queue = system::default_queue())
  72 {
  73     typedef typename
  74         std::iterator_traits<OutputIterator>::value_type output_type;
  75
  76     return detail::scan(first, last, result, true,
  77                         init, boost::compute::plus<output_type>(),
  78                         queue);
  79 }
  80
  81 /// \overload
  82 template<class InputIterator, class OutputIterator>
  83 inline OutputIterator
  84 exclusive_scan(InputIterator first,
  85                InputIterator last,
  86                OutputIterator result,
  87                command_queue &queue = system::default_queue())
  88 {
  89     typedef typename
  90         std::iterator_traits<OutputIterator>::value_type output_type;
  91
  92     return detail::scan(first, last, result, true,
  93                         output_type(0), boost::compute::plus<output_type>(),
  94                         queue);
  95 }
  96
  97 } // end compute namespace
  98 } // end boost namespace
  99
 100 #endif // BOOST_COMPUTE_ALGORITHM_EXCLUSIVE_SCAN_HPP