Урок 6 Измеряем и ускоряем

kutuzzzov

Nov 1st, 2022

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// main
#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) {
LOG_DURATION("Naive");
vector<int> res;
for (int i : source_vector) {
res.insert(res.begin(), i);
}
return res;
}
vector<int> ReverseVector2(const vector<int>& source_vector) {
LOG_DURATION("Good");
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) {
LOG_DURATION("Best");
return {source_vector.rbegin(), source_vector.rend()};
}
vector<int> ReverseVector4(const vector<int>& source_vector) {
LOG_DURATION("Your");
vector<int> res;
res.reserve(source_vector.size());
for (auto iterator = source_vector.rbegin(); iterator != source_vector.rend(); ++iterator) {
res.push_back(*iterator);
}
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());
}
// код измерения тут
if (n <= 100000) {
ReverseVector(rand_vector);
ReverseVector2(rand_vector);
} else {
ReverseVector2(rand_vector);
ReverseVector3(rand_vector);
ReverseVector4(rand_vector);
}
}
int main() {
Operate();
return 0;
}
// log_duration
#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();
};

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