switch与if 性能测试

测试结果：switch性能更高。

测试过程：新建一个Win32 Console Application, 在cpp文件中添加下面代码

#include "stdafx.h"
#include <Windows.h>

void SwitchTime(int a)
{
  for (int i = ; i < ; ++i)
  {
    switch(a)
    {
    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    case :
      a = ;
      break;

    default:
      a = ;
      break;
    }
  }
}

void IfTime(int a)
{
  for (int i = ; i < ; ++i)
  {
    if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else if ( == a)
    {
      a = ;
    }
    else
    {
      a = ;
    }
  }
}

int _tmain(int argc, _TCHAR* argv[])
{
  unsigned long switchBegin= ::GetTickCount();
  SwitchTime();
  unsigned long switchEnd= ::GetTickCount();

  unsigned long ifBegin= ::GetTickCount();
  IfTime();
  unsigned long ifEnd= ::GetTickCount();

  char result[];
  memset(result, , sizeof(result));
  sprintf(result, "SwitchTime: %d ms, IfTime: %d ms", switchEnd - switchBegin, ifEnd - ifBegin);
  MessageBoxA(NULL, result, "switch与if 性能测试", MB_OK);
  return ;
}

分别测试输入值0、10、19、20、-1、200

运行exe效果如下，