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;
}
int main()
{
std::vector<int> vi;
for(int i=0;i<1000;++i)
{
vi.push_back(10);
}
int sum=parallel_accumulate(vi.begin(),vi.end(),5);
std::cout<<"sum="<<sum<<std::endl;
}
int main(void)
{
std::vector<int> ivec;
for (int i = 0; i < 2000000; ++i) {
ivec.push_back(1);
}
std::chrono::system_clock::time_point b = std::chrono::system_clock::now();
std::cout << parallel_accumulate(ivec.begin(), ivec.end(), 0) << std::endl;
std::chrono::system_clock::time_point e = std::chrono::system_clock::now();
std::cout << (e - b).count() << std::endl;
b = e;
std::cout << std::accumulate(ivec.begin(), ivec.end(), 0) << std::endl;
e = std::chrono::system_clock::now();
std::cout << (e - b).count() << std::endl;
return 0;
}
T parallel_accumulate(Iterator first, Iterator last, T init)
{
unsigned long const length = std::distance(first, last);
unsigned long const max_chunk_size = 25;
if (length <= max_chunk_size) {
return std::accumulate(first, last, init);
} else {
Iterator mid_point = first;
std::advance(mid_point, length / 2);
std::future<T> first_half_result =
std::async(parallel_accumulate<Iterator, T>,
first, mid_point, init);
T second_half_result = parallel_accumulate(mid_point, last, T());
return first_half_result.get() + second_half_result;
}
}
