Спринт 9. Ускоряем for_each. Задание 1.

#include <algorithm>
#include <execution>
#include <iostream>
#include <list>
#include <random>
#include <string>
#include <string_view>
#include <type_traits>
#include <vector>
#include <future>

#include "log_duration.h"

using namespace std;

string GenerateWord(mt19937& generator, int max_length) {
    const int length = uniform_int_distribution(1, max_length)(generator);
    string word;
    word.reserve(length);
    for (int i = 0; i < length; ++i) {
        word.push_back(uniform_int_distribution('a', 'z')(generator));
    }
    return word;
}

template <template <typename> typename Container>
Container<string> GenerateDictionary(mt19937& generator, int word_count, int max_length) {
    vector<string> words;
    words.reserve(word_count);
    for (int i = 0; i < word_count; ++i) {
        words.push_back(GenerateWord(generator, max_length));
    }
    return Container(words.begin(), words.end());
}

struct Reverser {
    void operator()(string& value) const {
        reverse(value.begin(), value.end());
    }
};

template <typename Container, typename Function>
void Test(string_view mark, Container keys, Function function) {
    LOG_DURATION(mark);
    function(keys, Reverser{});
}

#define TEST(function) Test(#function, keys, function<remove_const_t<decltype(keys)>, Reverser>)

template <typename ForwardRange, typename Function>
void ForEach(ForwardRange& range, Function function) {
    int parts = 4;
    auto part_size = range.size() / parts;
    auto part_begin = range.begin();
    auto part_end = next(part_begin, part_size);

    vector<future<void>> result;
    for (int i = 0; i < parts; ++i, part_begin = part_end,
                                    part_end = (i == parts - 1
                                                ? range.end()
                                                : next(part_begin, part_size))) {
        result.push_back(async([function,
                                part_begin,
                                part_end] {
            for_each(std::execution::par,
                     part_begin,
                     part_end,
                     function);}));
    }
}

int main() {
    vector<string> strings = {"cat", "dog", "code"};

    ForEach(strings, [](string& s) {
        reverse(s.begin(), s.end());
    });

    for (string_view s : strings) {
        cout << s << " ";
    }
    cout << endl;

    mt19937 generator;
    const auto keys = GenerateDictionary<list>(generator, 50'000, 5'000);

    TEST(ForEach);

    return 0;
}