内存比较，这比较快？ [英] Memory comparison, which is faster?

问题描述

我有一个3D向量类。私有变量被定义：

 
 union {
 struct {
 double x; 
 double y; 
 double z; 
}; 
 double data [3]; 
}; 
 

在实现运算符==，哪个更快？

 
 return this-> x == vx && this-> y == vy && this-> z == vz; 
 
 
 
 
或
 
 return memcmp > data，v.data）== 0; 
 
 
 
解决方案
不幸的是，两者不等同。 （特别是NaN和有符号的零不使用FPU内部的逐位比较）。
 
 
 
所以你应该根据正确性而不是速度来选择。 b $ b
I have a 3D vector class. The private variables are defined:
union {
    struct {
        double x;
        double y;
        double z;
    };
    double data[3];
};
In implementing operator==, which is faster?
return this->x == v.x && this->y == v.y && this->z == v.z;
OR
return memcmp(this->data, v.data) == 0;

解决方案
Unfortunately the two aren't equivalent.  (Specifically NaNs and signed zeros don't use bitwise comparison inside the FPU).

So you should make your choice based on correctness, not speed.

                        
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