100 lines
2.9 KiB
C++
100 lines
2.9 KiB
C++
/*
|
||
Задача:
|
||
|
||
В данном примере написана функция getMax, которая находит максимум из чисел в векторе.
|
||
При этом вычисления проходят однопоточно.
|
||
|
||
|
||
Вам нужно написать функцию
|
||
|
||
uint64_t getMaxPar(int n, const std::vector<uint64_t>& v)
|
||
|
||
которая будет делать то же самое, но только использовать для этого n потоков.
|
||
*/
|
||
|
||
|
||
#include <iostream>
|
||
#include <thread>
|
||
#include <chrono>
|
||
#include <vector>
|
||
#include <random>
|
||
#include <algorithm>
|
||
#include <cstdint>
|
||
#include <functional>
|
||
using std::cout, std::endl, std::size_t;
|
||
using namespace std::chrono_literals;
|
||
|
||
uint64_t getMax(std::vector<uint64_t>::const_iterator first, std::vector<uint64_t>::const_iterator last)
|
||
{
|
||
uint64_t res = *first;
|
||
for (; first != last; first++)
|
||
if (*first > res)
|
||
res = *first;
|
||
return res;
|
||
}
|
||
|
||
uint64_t getMax(const std::vector<uint64_t>& v) {
|
||
return getMax(v.begin(), v.end());
|
||
}
|
||
|
||
struct maxBlock {
|
||
void operator() (std::vector<uint64_t>::const_iterator first, std::vector<uint64_t>::const_iterator last, uint64_t& res) {
|
||
res = getMax(first, last);
|
||
}
|
||
};
|
||
|
||
uint64_t getMax(int n, const std::vector<uint64_t>& v) {
|
||
std::vector<uint64_t> results(n);
|
||
std::vector<std::thread> threads(n - 1);
|
||
|
||
unsigned long const block_size = v.size() / n;
|
||
|
||
auto block_start = v.begin();
|
||
|
||
for (int i = 0; i < n - 1; ++i) {
|
||
auto block_end = block_start;
|
||
std::advance(block_end, block_size);
|
||
threads[i] = std::thread(maxBlock(),
|
||
block_start, block_end, std::ref(results[i]));
|
||
block_start = block_end;
|
||
}
|
||
maxBlock() (block_start, v.end(), results[n - 1]);
|
||
|
||
std::for_each(threads.begin(), threads.end(), std::mem_fn(&std::thread::join));
|
||
|
||
return getMax(results);
|
||
}
|
||
|
||
|
||
int main()
|
||
{
|
||
cout << "Generating numbers!" << endl;
|
||
std::vector<uint64_t> numbers(5e8);
|
||
numbers[0] = 123456789;
|
||
for (size_t i = 1; i < numbers.size(); ++i)
|
||
{
|
||
numbers[i] = numbers[i - 1] * i + 1;
|
||
}
|
||
cout << "Numbers generated!" << endl;
|
||
|
||
auto start = std::chrono::high_resolution_clock::now();
|
||
|
||
uint64_t m = getMax(numbers);
|
||
|
||
auto end = std::chrono::high_resolution_clock::now();
|
||
|
||
cout << "Maximum = " << m << endl;
|
||
cout << "Time to calclulate max = " << std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count()
|
||
<< " milliseconds." << endl;
|
||
|
||
/* Parallel */
|
||
start = std::chrono::high_resolution_clock::now();
|
||
|
||
m = getMax(4, numbers);
|
||
|
||
end = std::chrono::high_resolution_clock::now();
|
||
|
||
cout << "Maximum = " << m << endl;
|
||
cout << "Time to calclulate max = " << std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count()
|
||
<< " milliseconds." << endl;
|
||
}
|