int与unsigned char

Question

假设我们有一个运行100次的循环.用unsigned char而不是int用它的计数器有所作为吗？还用i += 1U而不是i++？或者编译器会处理这个问题？

Answer 1

在简单的情况下intvs unsigned char为我提供相同的代码:

    for ( unsigned char i = 0; i < 100; ++i ) {
01081001  mov         esi,64h  
01081006  jmp         main+10h (1081010h)  
01081008  lea         esp,[esp]  
0108100F  nop  
        std::cout << 1 << std::endl;
01081010  mov         eax,dword ptr [__imp_std::endl (108204Ch)]  
01081015  mov         ecx,dword ptr [__imp_std::cout (1082050h)]  
0108101B  push        eax  
0108101C  push        1  
0108101E  call        dword ptr [__imp_std::basic_ostream<char,std::char_traits<char> >::operator<< (1082044h)]  
01081024  mov         ecx,eax  
01081026  call        dword ptr [__imp_std::basic_ostream<char,std::char_traits<char> >::operator<< (1082048h)]  
0108102C  dec         esi  
0108102D  jne         main+10h (1081010h)  
    }
    return 0; 

您应该分析您的代码,然后优化慢速部分.不要以过早优化开始.