СПРИНТ № 6 | Профилируем и ускоряем | Урок 6: Измеряем и ускоряем

log_duration.h

#pragma once

#include <chrono>
#include <iostream>

#define PROFILE_CONCAT_INTERNAL(X, Y) X##Y
#define PROFILE_CONCAT(X, Y) PROFILE_CONCAT_INTERNAL(X, Y)
#define UNIQUE_VAR_NAME_PROFILE PROFILE_CONCAT(profileGuard, __LINE__)
#define LOG_DURATION(x) LogDuration UNIQUE_VAR_NAME_PROFILE(x)

class LogDuration {
public:
    // заменим имя типа std::chrono::steady_clock
    // с помощью using для удобства
    using Clock = std::chrono::steady_clock;

    LogDuration(const std::string& id) : id_(id) {
    }

    ~LogDuration() {
        using namespace std::chrono;
        using namespace std::literals;

        const auto end_time = Clock::now();
        const auto dur = end_time - start_time_;
        std::cerr << id_ << ": "s << duration_cast<milliseconds>(dur).count() << " ms"s << std::endl;
    }

private:
    const std::string id_;
    const Clock::time_point start_time_ = Clock::now();
};
***************************************************************************************************************************************

main.cpp

#include "log_duration.h"

#include <algorithm>
#include <chrono>
#include <cstdlib>
#include <iostream>
#include <vector>

using namespace std;

vector<int> ReverseVector(const vector<int>& source_vector) {
    vector<int> res;

    for (int i : source_vector) {
        res.insert(res.begin(), i);
    }

    return res;
}

vector<int> ReverseVector2(const vector<int>& source_vector) {
    vector<int> res;

    // будем проходить source_vector задом наперёд
    // с помощью обратного итератора
    for (auto iterator = source_vector.rbegin(); iterator != source_vector.rend(); ++iterator) {
        res.push_back(*iterator);
    }

    return res;
}

vector<int> ReverseVector3(const vector<int>& source_vector) {
    return { source_vector.rbegin(), source_vector.rend() };
}

vector<int> ReverseVector4(const std::vector<int>& source_vector) {
    std::vector<int> res(source_vector.size());
    std::reverse_copy(source_vector.begin(), source_vector.end(), res.begin());
    return res;
}

void Operate() {
    vector<int> rand_vector;
    int n;

    cin >> n;
    rand_vector.reserve(n);

    for (int i = 0; i < n; ++i) {
        rand_vector.push_back(rand());
    }

    if(n<=100000)
    {
        {
            LOG_DURATION("Naive");
            ReverseVector(rand_vector);
        }
        {
            LOG_DURATION("Good");
            ReverseVector2(rand_vector);
        }
    }
    else
    {
        {
            LOG_DURATION("Good");
            ReverseVector2(rand_vector);
        }
        {
            LOG_DURATION("Best");
            ReverseVector3(rand_vector);
        }
        {
            LOG_DURATION("Your");
            ReverseVector4(rand_vector);
        }
    }
}

int main() {
    Operate();
    return 0;
}