所以我搞乱了Visual C ++ 2015，我注意到Visual C ++似乎编译常量和访问它们的方式存在问题。
请考虑以下事项：
yourList.add()顶部部分比底部部分运行更慢（增加约75％的额外时间），唯一的区别是#include "stdafx.h"
#include <stdio.h>
#include <Windows.h>
#define ITERATIONS 500000
#define GET_START_TIME QueryPerformanceCounter(&StartingTime);
#define GET_END_TIME QueryPerformanceCounter(&EndingTime);
#define CALC_DIFF_TIME ElapsedMicroseconds.QuadPart = EndingTime.QuadPart - StartingTime.QuadPart; ElapsedMicroseconds.QuadPart *= 1000000; ElapsedMicroseconds.QuadPart /= Frequency.QuadPart;
int main()
{
short results[ITERATIONS];
const int n = 5;
int m = 5;
LARGE_INTEGER StartingTime, EndingTime, ElapsedMicroseconds;
LARGE_INTEGER Frequency;
QueryPerformanceFrequency(&Frequency);
// This loop seems to take about 1400 us on my computer.
printf("Beginning loop over %i iterations with n constant.\n", ITERATIONS);
GET_START_TIME;
for (int i = 0; i < ITERATIONS; i++)
{
int statement = i % 10;
if (statement == 0)
results[i] = n * 0;
else if (statement == 4)
results[i] = n * 4;
else if (statement == 2)
results[i] = n * 2;
else if (statement == 5)
results[i] = n * 5;
else if (statement == 7)
results[i] = n * 7;
else if (statement == 6)
results[i] = n * 6;
else if (statement == 1)
results[i] = n * 1;
else if (statement == 3)
results[i] = n * 3;
else if (statement == 9)
results[i] = n * 9;
else if (statement == 8)
results[i] = n * 8;
}
GET_END_TIME;
CALC_DIFF_TIME;
printf("Finished in %lld us.\n", ElapsedMicroseconds.QuadPart);
// This one takes about 800 us on my computer.
printf("Beginning loop over %i iterations with m variable.\n", ITERATIONS);
GET_START_TIME;
for (int i = 0; i < ITERATIONS; i++)
{
int statement = i % 10;
if (statement == 0)
results[i] = m * 0;
else if (statement == 4)
results[i] = m * 4;
else if (statement == 2)
results[i] = m * 2;
else if (statement == 5)
results[i] = m * 5;
else if (statement == 7)
results[i] = m * 7;
else if (statement == 6)
results[i] = m * 6;
else if (statement == 1)
results[i] = m * 1;
else if (statement == 3)
results[i] = m * 3;
else if (statement == 9)
results[i] = m * 9;
else if (statement == 8)
results[i] = m * 8;
}
GET_END_TIME;
CALC_DIFF_TIME;
printf("Finished in %lld us.\n", ElapsedMicroseconds.QuadPart);
getchar();
return 0;
}
是n而不是常规const int。
我的问题：这是设计，还是Visual C ++中的缺陷/错误？这是否与我将结果分配给int？
经过进一步调试后，似乎如果我将short数组更改为short数组，则常规变量的速度从~800us增加到1400us，int值
另外一个问题：为什么将常规变量算术结果的更长分配给const数组，而不是int数组，为什么呢？ short花费相同的时间吗？
附加说明：进一步的故障排除显示这只发生在发布模式，而不是在调试模式下。
我已为所有感兴趣的人提供了const int个文件on Gist。