1 // Copyright (C) 2014 Vicente Botet
2 //
3 // Distributed under the Boost Software License, Version 1.0. (See accompanying
4 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
5
6 #include <boost/config.hpp>
7
8 #define BOOST_THREAD_VERSION 4
9 #define BOOST_THREAD_PROVIDES_EXECUTORS
10 #define BOOST_THREAD_USES_LOG_THREAD_ID
11 #define BOOST_THREAD_QUEUE_DEPRECATE_OLD
12 #if ! defined BOOST_NO_CXX11_DECLTYPE
13 #define BOOST_RESULT_OF_USE_DECLTYPE
14 #endif
15
16 #include <boost/thread/executors/basic_thread_pool.hpp>
17 #include <boost/thread/future.hpp>
18
19 #include <numeric>
20 #include <algorithm>
21 #include <functional>
22 #include <iostream>
23 #include <vector>
24
25 #if defined(BOOST_THREAD_PROVIDES_VARIADIC_THREAD)
26
27 template<typename Iterator,typename T>
28 struct accumulate_block
29 {
30 //typedef T result_type;
operator ()accumulate_block31 T operator()(Iterator first,Iterator last)
32 {
33 return std::accumulate(first,last,T());
34 }
35 };
36
37 template<typename Iterator,typename T>
parallel_accumulate(Iterator first,Iterator last,T init)38 T parallel_accumulate(Iterator first,Iterator last,T init)
39 {
40 unsigned long const length=static_cast<unsigned long>(std::distance(first,last));
41
42 if(!length)
43 return init;
44
45 unsigned long const block_size=25;
46 unsigned long const num_blocks=(length+block_size-1)/block_size;
47
48 boost::csbl::vector<boost::future<T> > futures(num_blocks-1);
49 boost::basic_thread_pool pool;
50
51 Iterator block_start=first;
52 for(unsigned long i=0;i<(num_blocks-1);++i)
53 {
54 Iterator block_end=block_start;
55 std::advance(block_end,block_size);
56 futures[i]=boost::async(pool, accumulate_block<Iterator,T>(), block_start, block_end);
57 block_start=block_end;
58 }
59 T last_result=accumulate_block<Iterator,T>()(block_start,last);
60 T result=init;
61 for(unsigned long i=0;i<(num_blocks-1);++i)
62 {
63 result+=futures[i].get();
64 }
65 result += last_result;
66 return result;
67 }
68
69
main()70 int main()
71 {
72 try
73 {
74 const int s = 1001;
75 std::vector<int> vec;
76 vec.reserve(s);
77 for (int i=0; i<s;++i)
78 vec.push_back(1);
79 int r = parallel_accumulate(vec.begin(), vec.end(),0);
80 std::cout << r << std::endl;
81
82 }
83 catch (std::exception& ex)
84 {
85 std::cout << "ERROR= " << ex.what() << "" << std::endl;
86 return 1;
87 }
88 catch (...)
89 {
90 std::cout << " ERROR= exception thrown" << std::endl;
91 return 2;
92 }
93 return 0;
94 }
95
96 #else
97 ///#warning "This compiler doesn't supports variadics"
main()98 int main()
99 {
100 return 0;
101 }
102 #endif
103