C++17 Parallel Algorithms - About the Book

#include <vector>
#include <execution>

We have to load Threading Building Blocks library that under the hood does the actual parallelization:

#pragma cling load("libtbb.so.2")

const std::vector<double> v(10'000'007, 0.1);

%%timeit
std::reduce(std::execution::seq, v.cbegin(), v.cend());

Output

203 ms +- 46.3 ms per loop (mean +- std. dev. of 7 runs 10 loops each)

%%timeit
std::reduce(std::execution::par, v.cbegin(), v.cend());

Output

54.5 ms +- 1.62 ms per loop (mean +- std. dev. of 7 runs 10 loops each)

auto s = std::reduce(std::execution::par, v.cbegin(), v.cend());
s

Output

1000000.7