各种快速SQRT

最新推荐文章于 2022-08-22 10:53:17 发布

iteye_3055

最新推荐文章于 2022-08-22 10:53:17 发布

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博客展示了平方根与倒数平方根的浮点计算函数代码。包含mysqrt函数用于计算平方根，以及InvSqrt_Lomont和InvSqrt函数用于计算倒数平方根，通过对浮点数和整数部分的转换及特定运算实现计算。

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float mysqrt(float x)
{
union
{
int intPart;
float floatPart;
} convertor;
union
{
int intPart;
float floatPart;
} convertor2;

convertor.floatPart = x;
convertor2.floatPart = x;
convertor.intPart = 0x1FBCF800 + (convertor.intPart >> 1);
convertor2.intPart = 0x5f3759df - (convertor2.intPart >> 1);
return 0.5f*(convertor.floatPart + (x * convertor2.floatPart));
}

float InvSqrt_Lomont(float x)
{
float xhalf = 0.5f*x;
int i = *(int*)&x;
i = 0x5f375a86 - (i>>1);
x = *(float*)&i;
x = x*(1.5f-xhalf*x*x);
// x = x*(1.5f-xhalf*x*x); // added precision
return x;
} // InvSqrt_Lomont

float InvSqrt (float x)
{
float xhalf = 0.5f*x;
int i = *(int*)&x;
i = 0x5f3759df - (i >> 1);
x = *(float*)&i;
x = x*(1.5f - xhalf*x*x);
return x;
}