简单程序的性能（生成created_at唯一随机混洗整数然后对它们进行排序）比较慢，当我在重新编译后第二次从#include "Snake.h"
Snake::Snake(){
Snakey.setSize(sf::Vector2f(10, 10));
Snakey.setFillColor(sf::Color(0,255,0));
enter code here
Snakey.setPosition(180,60);
BodyList.push_back(Body);
}
Snake::~Snake(){
BodyList.clear();
}
void Snake::Draw(sf::RenderWindow &window){
window.draw(Snakey);
for (sf::RectangleShape& Body : BodyList){
window.draw(Body);
}
BodyList.erase(BodyList.begin());
BodyList.push_back(Body);
}
void Snake::Grow(){
Body.setSize(sf::Vector2f(10, 10));
Body.setFillColor(sf::Color(0,100,0));
Body.setPosition(Snakey.getPosition().x,Snakey.getPosition().y);
BodyList.push_back(Body);
}
void Snake::Move(sf::Event event, sf::RenderWindow &window){
if (sf::Keyboard::isKeyPressed && sf::Keyboard::Left == event.key.code && Dir != "Right"){
Snakey.move(-10, 0);
Body.move(-10,0);
Dir = ("Left");
}
else if (sf::Keyboard::isKeyPressed && sf::Keyboard::Key::Right == event.key.code && Dir != "Left"){
Snakey.move(10, 0);
Body.move(10,0);
Dir = ("Right");
}
else if (sf::Keyboard::isKeyPressed && sf::Keyboard::Key::Up == event.key.code && Dir != "Down"){
Snakey.move(0, -10);
Body.move(0,-10);
Dir = ("Up");
}
else if (sf::Keyboard::isKeyPressed && sf::Keyboard::Key::Down == event.key.code && Dir != "Up"){
Snakey.move(0, 10);
Body.move(0,10);
Dir = ("Down");
}
else if (sf::Keyboard::isKeyPressed && sf::Keyboard::Key::Down == event.key.code && Dir == "Up" ||
sf::Keyboard::isKeyPressed && sf::Keyboard::Key::Up == event.key.code && Dir == "Down" ||
sf::Keyboard::isKeyPressed && sf::Keyboard::Key::Right == event.key.code && Dir == "Left"||
sf::Keyboard::isKeyPressed && sf::Keyboard::Left == event.key.code && Dir == "Right"){
window.close();
}
}
void Snake::TailCollision(sf::RenderWindow &window){
for (int i = 0 ; i < BodyList.size(); i++){
if ((Snakey.getPosition().x == BodyList[i].getPosition().x && Snakey.getPosition().y == BodyList[i].getPosition().y)&&
(BodyList[i].getPosition().x != BodyList.back().getPosition().x &&
BodyList[i].getPosition().y != BodyList.back().getPosition().y)){
window.close();
}
}
}
sf::RectangleShape Snake::GetShape(){
return Snakey;
}
运行它（以及所有下一次直到下一次重新编译）
public interface IteratorWithIndex<T> extends Iterator<T> {
int index();
}
说，第一次打印;
document.execCommand('insertImage', false, "C://issue.jpg");
然后：
1 200 000还有另一个（还有第二个和第三个）：
Qt Creator如果我重新编译程序，那么所有重复编译。
如果我重新编译程序并从控制台运行它，那么所有输出都从#include <iostream>
#include <random>
#include <algorithm>
#include <chrono>
#include <iterator>
#include <cstdint>
using size_type = std::uint32_t;
alignas(64) size_type v[1200000];
// behaviour really not depends on CPU affinity
#ifdef __linux__
#include <sched.h>
#endif
int main()
{
#ifdef __linux__
{
cpu_set_t m;
int status;
CPU_ZERO(&m);
CPU_SET(0, &m);
status = sched_setaffinity(0, sizeof(m), &m);
if (status != 0) {
perror("sched_setaffinity");
}
}
#endif
std::mt19937 g(0);
for (size_type i = 1; i < std::size(v); ++i) {
v[i] = std::exchange(v[g() % i], i);
}
for (size_type i = 0; i < 10; ++i) { // first output not depends on number of iterations
auto start = std::chrono::high_resolution_clock::now();
std::sort(std::begin(v), std::end(v));
std::cout << std::chrono::duration_cast< std::chrono::microseconds >(std::chrono::high_resolution_clock::now() - start).count() << std::endl;
}
}
附近的值开始，即使是第一个，看起来像下一个：
97896
26069
25628
25771
25863
25722
25976
25855
25687
25735
如果嘀咕很多，我在137238
35056
34880
34468
34746
27309
25781
25932
25502
25383
w / 8GB RAM，SSD上的Ubuntu Desktop 16.04.3 64位上构建并运行以上程序。没有root流行且没有调试器。我使用137648
35086
34966
26005
26305
26435
25683
25440
25981
25632
，137000和137207
35059
35035
34844
34563
34586
34466
34132
34327
34487
。
我期望反向结果，因为（可能）分支预测缓存或一些其他缓存（如果在相同代码的连续运行之间可能的话），但结果令人沮丧。