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_DETAIL_COUNT_IF_WITH_REDUCE_HPP
12 #define BOOST_COMPUTE_ALGORITHM_DETAIL_COUNT_IF_WITH_REDUCE_HPP
13
14 #include <boost/compute/algorithm/reduce.hpp>
15 #include <boost/compute/iterator/transform_iterator.hpp>
16 #include <boost/compute/types/fundamental.hpp>
17
18 namespace boost {
19 namespace compute {
20 namespace detail {
21
22 template<class Predicate, class Arg>
23 struct invoked_countable_predicate
24 {
invoked_countable_predicateboost::compute::detail::invoked_countable_predicate25 invoked_countable_predicate(Predicate p, Arg a)
26 : predicate(p), arg(a)
27 {
28 }
29
30 Predicate predicate;
31 Arg arg;
32 };
33
34 template<class Predicate, class Arg>
operator <<(meta_kernel & kernel,const invoked_countable_predicate<Predicate,Arg> & expr)35 inline meta_kernel& operator<<(meta_kernel &kernel,
36 const invoked_countable_predicate<Predicate, Arg> &expr)
37 {
38 return kernel << "(" << expr.predicate(expr.arg) << " ? 1 : 0)";
39 }
40
41 // the countable_predicate wraps Predicate and converts its result from
42 // bool to ulong so that it can be used with reduce()
43 template<class Predicate>
44 struct countable_predicate
45 {
46 typedef ulong_ result_type;
47
countable_predicateboost::compute::detail::countable_predicate48 countable_predicate(Predicate predicate)
49 : m_predicate(predicate)
50 {
51 }
52
53 template<class Arg>
operator ()boost::compute::detail::countable_predicate54 invoked_countable_predicate<Predicate, Arg> operator()(const Arg &arg) const
55 {
56 return invoked_countable_predicate<Predicate, Arg>(m_predicate, arg);
57 }
58
59 Predicate m_predicate;
60 };
61
62 // counts the number of elements matching predicate using reduce()
63 template<class InputIterator, class Predicate>
count_if_with_reduce(InputIterator first,InputIterator last,Predicate predicate,command_queue & queue)64 inline size_t count_if_with_reduce(InputIterator first,
65 InputIterator last,
66 Predicate predicate,
67 command_queue &queue)
68 {
69 countable_predicate<Predicate> reduce_predicate(predicate);
70
71 ulong_ count = 0;
72 ::boost::compute::reduce(
73 ::boost::compute::make_transform_iterator(first, reduce_predicate),
74 ::boost::compute::make_transform_iterator(last, reduce_predicate),
75 &count,
76 ::boost::compute::plus<ulong_>(),
77 queue
78 );
79
80 return static_cast<size_t>(count);
81 }
82
83 } // end detail namespace
84 } // end compute namespace
85 } // end boost namespace
86
87 #endif // BOOST_COMPUTE_ALGORITHM_DETAIL_COUNT_IF_WITH_REDUCE_HPP
88