The following code example is taken from the book
C++17 - The Complete Guide
by Nicolai M. Josuttis,
Leanpub, 2017
The code is licensed under a
Creative Commons Attribution 4.0 International License.
// raw code
#include <iostream>
#include <vector>
#include <numeric> // for reduce()
#include <execution>
void printSum(long num)
{
// create coll with num sequences of 1 2 3 4:
std::vector<long> coll;
coll.reserve(num * 4);
for (long i=0; i < num; ++i) {
coll.insert(coll.end(), {1, 2, 3, 4});
}
auto squaredSum = [] (auto sum, auto val) {
return sum + val * val;
};
auto sum = std::reduce(std::execution::par,
coll.begin(), coll.end(),
0L,
squaredSum);
std::cout << "reduce(): " << sum << '\n';
}
int main()
{
printSum(1);
printSum(1000);
printSum(1000000);
printSum(10000000);
}