switch与if 性能测试

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


 void SwitchTime()
 {     
   for (int i = 0; i < 10000000; ++i)
   {
     int a = 19;
     switch(a)
     {
     case 0:
       a = 0;
       break;

     case 1:
       a = 0;
       break;

     case 2:
       a = 0;
       break;

     case 3:
       a = 0;
       break;

     case 4:
       a = 0;
       break;

     case 5:
       a = 0;
       break;

     case 6:
       a = 0;
       break;

     case 7:
       a = 0;
       break;

     case 8:
       a = 0;
       break;

     case 9:
       a = 0;
       break;

     case 10:
       a = 0;
       break;

     case 11:
       a = 0;
       break;

     case 12:
       a = 0;
       break;

     case 13:
       a = 0;
       break;

     case 14:
       a = 0;
       break;

     case 15:
       a = 0;
       break;

     case 16:
       a = 0;
       break;

     case 17:
       a = 0;
       break;

     case 18:
       a = 0;
       break;

     case 19:
       a = 0;
       break;
     }
   }   
 }

 void IfTime()
 {      
   for (int i = 0; i < 10000000; ++i)
   {
     int a = 19;
     if (0 == a)
     {
       a = 0;
     }
     else if (1 == a)
     {
       a = 0;
     }
     else if (2 == a)
     {
       a = 0;
     }
     else if (3 == a)
     {
       a = 0;
     }
     else if (4 == a)
     {
       a = 0;
     }
     else if (5 == a)
     {
       a = 0;
     }
     else if (6 == a)
     {
       a = 0;
     }
     else if (7 == a)
     {
       a = 0;
     }
     else if (8 == a)
     {
       a = 0;
     }
     else if (9 == a)
     {
       a = 0;
     }
     else if (10 == a)
     {
       a = 0;
     }
     else if (11 == a)
     {
       a = 0;
     }
     else if (12 == a)
     {
       a = 0;
     }
     else if (13 == a)
     {
       a = 0;
     }
     else if (14 == a)
     {
       a = 0;
     }
     else if (15 == a)
     {
       a = 0;
     }
     else if (16 == a)
     {
       a = 0;
     }
     else if (17 == a)
     {
       a = 0;
     }
     else if (18 == a)
     {
       a = 0;
     }
     else if (19 == a)
     {
       a = 0;
     }     
   }   
 }

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[128];
  memset(result, 0, 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 0;
}