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parallel_accumulate.cpp
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102 lines (87 loc) · 2.38 KB
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// Copyright (C) 2014 Vicente Botet
//
// 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)
#include <boost/config.hpp>
#define BOOST_THREAD_VERSION 4
#define BOOST_THREAD_PROVIDES_EXECUTORS
#define BOOST_THREAD_USES_LOG_THREAD_ID
#define BOOST_THREAD_QUEUE_DEPRECATE_OLD
#if ! defined BOOST_NO_CXX11_DECLTYPE
#define BOOST_RESULT_OF_USE_DECLTYPE
#endif
#include <boost/thread/executors/basic_thread_pool.hpp>
#include <boost/thread/future.hpp>
#include <numeric>
#include <algorithm>
#include <functional>
#include <iostream>
#include <vector>
#if defined(BOOST_THREAD_PROVIDES_VARIADIC_THREAD)
template<typename Iterator,typename T>
struct accumulate_block
{
//typedef T result_type;
T operator()(Iterator first,Iterator last)
{
return std::accumulate(first,last,T());
}
};
template<typename Iterator,typename T>
T parallel_accumulate(Iterator first,Iterator last,T init)
{
unsigned long const length=static_cast<unsigned long>(std::distance(first,last));
if(!length)
return init;
unsigned long const block_size=25;
unsigned long const num_blocks=(length+block_size-1)/block_size;
boost::csbl::vector<boost::future<T> > futures(num_blocks-1);
boost::basic_thread_pool pool;
Iterator block_start=first;
for(unsigned long i=0;i<(num_blocks-1);++i)
{
Iterator block_end=block_start;
std::advance(block_end,block_size);
futures[i]=boost::async(pool, accumulate_block<Iterator,T>(), block_start, block_end);
block_start=block_end;
}
T last_result=accumulate_block<Iterator,T>()(block_start,last);
T result=init;
for(unsigned long i=0;i<(num_blocks-1);++i)
{
result+=futures[i].get();
}
result += last_result;
return result;
}
int main()
{
try
{
const int s = 1001;
std::vector<int> vec;
vec.reserve(s);
for (int i=0; i<s;++i)
vec.push_back(1);
int r = parallel_accumulate(vec.begin(), vec.end(),0);
std::cout << r << std::endl;
}
catch (std::exception& ex)
{
std::cout << "ERROR= " << ex.what() << "" << std::endl;
return 1;
}
catch (...)
{
std::cout << " ERROR= exception thrown" << std::endl;
return 2;
}
return 0;
}
#else
///#warning "This compiler doesn't supports variadics"
int main()
{
return 0;
}
#endif