简单测试Placement new 对比 new 的性能

 1 #include <iostream>
 2 #include <time.h>
 3 #include <stdlib.h>
 4
 5 using namespace std;
 6
 7 #define LOOP_COUNT 500000
 8 int main()
 9 {
10     char buf[10000] = {0};
11
12     int* obj = NULL;
13
14     int i = LOOP_COUNT;
15
16     clock_t start = clock();
17     while(i--)
18     {
19         obj = new (buf) int [1000];
20
21         obj = NULL;
22     }
23     clock_t end = clock();
24
25     cout << "Placement new : " << end - start << " ms" << endl;
26
27
28     i = LOOP_COUNT;
29     start = clock();
30     while(i--)
31     {
32         obj = new int [1000];
33         //delete obj;
34         obj = NULL;
35     }
36     end = clock();
37
38     cout << "Normal new : " << end - start << " ms" << endl;
39 }

Test case 1. new 操作不delete内存

//////////////// output

Placement new : 0
Normal new : 3234

Test case 2. new 操作， delete内存

//////////////// output

Placement new : 0
Normal new : 1594