Vector size performance problems

Catalog

sentence null 

  Use visual studio test

Use Clion Configured vs 2019 

loop

---

Test use vector.size And Use Sign a

Use Flag bit judgment vector  Is it null, Thousand will be tested separately 、 ten thousand 、 One hundred thousand 、 Millions of time-consuming comparison . 

sentence null 

After testing , Discover the use of visual studio Than clion Configured visual studio More time saving ,

The header file ：RelevantSizeFuncTest.h

//
// Created by ly on 2022/7/12.  size  Performance testing 
//

#ifndef CPLUSPLUSTESTPRJ_RELEVANTSIZEFUNCTEST_H
#define CPLUSPLUSTESTPRJ_RELEVANTSIZEFUNCTEST_H
#include <vector>
#include <cstring>
#include <string>

using namespace std;
class RelevantSizeFuncTest {
public:
    RelevantSizeFuncTest();
    ~RelevantSizeFuncTest();
    void getFlagSizeTest();
    void getSizeTest();
    void getEmptyTest();
    void getSizeTestNewT();
private:
    std::vector<string> strListFlag;
    std::vector<string> strList;
    std::vector<string> strEmList;

};


#endif //CPLUSPLUSTESTPRJ_RELEVANTSIZEFUNCTEST_H

Source file ：RelevantSizeFuncTest.cpp  

//
// Created by caeri on 2022/7/12.
//

#include<iostream>
#include <thread>
#include "PerformanceTest/RelevantSizeFuncTest.h"
RelevantSizeFuncTest::RelevantSizeFuncTest() {


}

RelevantSizeFuncTest::~RelevantSizeFuncTest() {


}
const int cunt = 1000;
void RelevantSizeFuncTest::getFlagSizeTest() {
    auto start = clock();
    bool isEmpty = false;
    for(int i = 0; i < cunt; i++){
        this->strListFlag.push_back(to_string(i));
        if(!isEmpty) isEmpty = true;
    }
    if(isEmpty){
        string s = "124";
    }
    auto end = clock();
    double interval = ((double)end - start) / CLOCKS_PER_SEC;
    cout << " Flag bit takes time ： " << interval * 1000 << "ms" << endl;
}

void RelevantSizeFuncTest::getSizeTest() {
    auto start = clock();

    for(int i = 0; i < cunt; i++){
        this->strList.push_back(to_string(i));
    }
    if(this->strList.size() > 0){
        string s = "124";
    }
    auto end = clock();
    double interval = ((double)end - start) / CLOCKS_PER_SEC;
    cout << "size Time consuming ： " <<  interval * 1000 << "ms" << endl;
}

void RelevantSizeFuncTest::getEmptyTest() {
    auto start = clock();

    for(int i = 0; i < cunt; i++){
        this->strEmList.push_back(to_string(i));
    }
    if(!this->strEmList.empty()){
        string s = "124";
    }
    auto end = clock();
    double interval = ((double)end - start) / CLOCKS_PER_SEC;
    cout << "empty Time consuming ： " <<  interval * 1000 << "ms" << endl;
}

void RelevantSizeFuncTest::getSizeTestNewT() {
    //thread t1(&RelevantSizeFuncTest::getSizeTest,this);
}

  Use visual studio test

  It is found that there is a time difference of ten million levels Not big .

  Million level

Use Clion Configured vs 2019 

Use secondary configuration , Found running slowly （ Not recommended ）

  After many tests ： Thousand level Time consuming Little difference

  5000 level ： The difference is about how many milliseconds

  10000 level test ： The result is not very stable , Most of the time , There is little difference in time . The time consumption of the logo is relatively stable . Most of the time , The difference is tens of milliseconds .

One hundred thousand , Flag bits are probably saved 2 Thousands of milliseconds  

 

  Million level ： The flag bit takes the least time

  After testing , Use the flag bit to judge null , From the order of 100000 , Flag bits take less time , The test is not accurate , The larger the order of magnitude , The less time the flag bit takes . Use only clion test , The result is not correct , Abandoning

Centralized methods take little time

Be careful ： I used to use multithreaded testing , But multithreading of test results is more time-consuming .

loop

But in c++ in , In general , Functions in the class that define the function body will automatically be regarded as inline functions by the compiler , The feature of inline function is that it will insert code segments when the program is running , That is, expand the contents of the function where the inline function is called , This saves the cost of function calls .

loop , Not recommended for(int i = 0; i < list.size():i++) 

//
// Created by ly on 2022/7/12.  size  Performance testing 
//

#ifndef CPLUSPLUSTESTPRJ_RELEVANTSIZEFUNCTEST_H
#define CPLUSPLUSTESTPRJ_RELEVANTSIZEFUNCTEST_H
#include <vector>
#include <cstring>
#include <string>

using namespace std;
const int cunt = 10000000;
class RelevantSizeFuncTest {
public:
    RelevantSizeFuncTest();
    ~RelevantSizeFuncTest();
    void getFlagSizeTest();
    void getSizeTest();
    void getEmptyTest();
    void getSizeTestNewT();
    void useSizeTest();
    void useTempTest();
private:
    std::vector<string> strListFlag;
    std::vector<string> strList;
    std::vector<string> strEmList;
    std::vector<string> comStrList;

};


#endif //CPLUSPLUSTESTPRJ_RELEVANTSIZEFUNCTEST_H

//
// Created by caeri on 2022/7/12.
//

#include<iostream>
#include <thread>
#include "PerformanceTest/RelevantSizeFuncTest.h"
RelevantSizeFuncTest::RelevantSizeFuncTest() {
    for (int i = 0; i < cunt; i++) {
        comStrList.push_back(to_string(i));
    }

}

RelevantSizeFuncTest::~RelevantSizeFuncTest() {


}

void RelevantSizeFuncTest::getFlagSizeTest() {
    auto start = clock();
    bool isEmpty = false;
    for(int i = 0; i < cunt; i++){
        this->strListFlag.push_back(to_string(i));
        if(!isEmpty) isEmpty = true;
    }
    if(isEmpty){
        string s = "124";
    }
    auto end = clock();
    double interval = ((double)end - start) / CLOCKS_PER_SEC;
    cout << " Flag bit takes time ： " << interval * 1000 << "ms" << endl;
}

void RelevantSizeFuncTest::getSizeTest() {
    auto start = clock();

    for(int i = 0; i < cunt; i++){
        this->strList.push_back(to_string(i));
    }
    if(this->strList.size() > 0){
        string s = "124";
    }
    auto end = clock();
    double interval = ((double)end - start) / CLOCKS_PER_SEC;
    cout << "size Time consuming ： " <<  interval * 1000 << "ms" << endl;
}

void RelevantSizeFuncTest::getEmptyTest() {
    auto start = clock();

    for(int i = 0; i < cunt; i++){
        this->strEmList.push_back(to_string(i));
    }
    if(!this->strEmList.empty()){
        string s = "124";
    }
    auto end = clock();
    double interval = ((double)end - start) / CLOCKS_PER_SEC;
    cout << "empty Time consuming ： " <<  interval * 1000 << "ms" << endl;
}

void RelevantSizeFuncTest::getSizeTestNewT() {
    //thread t1(&RelevantSizeFuncTest::getSizeTest,this);
}

void RelevantSizeFuncTest::useSizeTest() {
    auto start = clock();

    for (int i = 0; i < this->comStrList.size(); i++) {
        //string s = "124";
    }
    auto end = clock();
    double interval = ((double)end - start) / CLOCKS_PER_SEC;
    cout << "size Time consuming ： " << interval * 1000 << "ms" << endl;
}
void RelevantSizeFuncTest::useTempTest() {
    auto start = clock();
    int tempCnt = this->comStrList.size();
    for (int i = 0; i < tempCnt; i++) {
        //string s = "124";
    }
    auto end = clock();
    double interval = ((double)end - start) / CLOCKS_PER_SEC;
    cout << "tempCnt Time consuming ： " << interval * 1000 << "ms" << endl;
}