我进行了一项测试,以通过将其值打印到CLI中来查看访问数组元素和单个对象之间的区别:
#include <iostream>
#include <chrono>
#include <iomanip>
int main()
{
int a[10] = {1,2,3,4,5,6,7,8,9,10};
int v1 = 1;
int v2 = 2;
int v3 = 3;
int v4 = 4;
int v5 = 5;
int v6 = 6;
int v7 = 7;
int v8 = 8;
int v9 = 9;
int v10 = 10;
std::cout << "Array output:" << std::endl << std::endl;
auto t_start1 = std::chrono::high_resolution_clock::now();
std::cout << "1. value: " << a[0] << std::endl;
std::cout << "2. value: " << a[1] << std::endl;
std::cout << "3. value: " << a[2] << std::endl;
std::cout << "4. value: " << a[3] << std::endl;
std::cout << "5. value: " << a[4] << std::endl;
std::cout << "6. value: " << a[5] << std::endl;
std::cout << "7. value: " << a[6] << std::endl;
std::cout << "8. value: " << a[7] << std::endl;
std::cout << "9. value: " << a[8] << std::endl;
std::cout << "10. value: " << a[9] << std::endl;
auto t_end1 = std::chrono::high_resolution_clock::now();
std::cout << std::endl;
std::cout << "Variable output:" << std::endl << std::endl;
auto t_start2 = std::chrono::high_resolution_clock::now();
std::cout << "1. value: " << v1 << std::endl;
std::cout << "2. value: " << v2 << std::endl;
std::cout << "3. value: " << v3 << std::endl;
std::cout << "4. value: " << v4 << std::endl;
std::cout << "5. value: " << v5 << std::endl;
std::cout << "6. value: " << v6 << std::endl;
std::cout << "7. value: " << v7 << std::endl;
std::cout << "8. value: " << v8 << std::endl;
std::cout << "9. value: " << v9 << std::endl;
std::cout << "10. value: " << v10 << std::endl;
auto t_end2 = std::chrono::high_resolution_clock::now();
std::cout<< std::endl << "Time passed with array: "
<< std::chrono::duration<double, std::milli>(t_end1-t_start1).count()
<< " ms\n" << std::endl;
std::cout<< std::endl << "Time passed with variables: "
<< std::chrono::duration<double, std::milli>(t_end2-t_start2).count()
<< " ms\n" << std::endl;
return 0;
}
在第一个实现上(在Windows 10下为MingW / g ++,cmd.exe),数组元素内部值的打印平均比使用单个标量对象慢3 毫秒。
适用于Windows的表格,g ++ / MingW:
。]Array Elements: Single Objects: 1. Run 13.9609 ms 9.529 ms 2. Run 11.9031 ms 8.0936 ms 3. Run 13.3706 ms 9.5264 ms 4. Run 12.5302 ms 8.4723 ms 5. Run 14.4679 ms 9.9688 ms 6. Run 12.3989 ms 8.4326 ms 7. Run 12.8719 ms 10.1851 ms 8. Run 10.9138 ms 7.4481 ms 9. Run 12.8971 ms 9.4094 ms 10. Run 11.9045 ms 7.9391 ms 11. Run 9.9192 ms 8.4047 ms 12. Run 13.4106 ms 10.0296 ms
在Linux Ubuntu下的第二种实现g ++中,数组元素内部值的打印平均比使用单个标量对象慢3 微秒
Linux Ubuntu表格,g ++:
Array Elements: Single Objects: 1. Run 0.013 ms 0.008 ms 2. Run 0.012 ms 0.007 ms 3. Run 0.013 ms 0.008 ms 4. Run 0.014 ms 0.009 ms 5. Run 0.012 ms 0.008 ms 6. Run 0.013 ms 0.008 ms 7. Run 0.013 ms 0.009 ms 8. Run 0.014 ms 0.009 ms 9. Run 0.012 ms 0.008 ms 10. Run 0.013 ms 0.009 ms 11. Run 0.012 ms 0.009 ms 12. Run 0.012 ms 0.008 ms
我的问题:
*信息:我不知道与特定语言无关,对数组元素的访问是否平均较慢。
我进行了一项测试,以查看将数组元素和单个对象的值打印到CLI中的方法:#include
std::endl
)所花费的时间,这涉及系统调用。 从数组中加载元素比这要短得多。从i1-i9900KS上的内存中,从L1缓存中加载CPU寄存器需要4个CPU周期(在5GHz CPU上不到1纳秒)-215个CPU周期。
使情况更糟的是,它甚至可能不从数组或变量中读取值,因为该值已在编译时知道。在两种情况下都可能只使用常量。