Fast inverse square root
Fast inverse square root , sometimes referred to as Fast InvSqrt or by the hexadecimal constant 0x5F3759DF , is an algorithm that estimates , the reciprocal ( or multiplicative inverse ) of the square root of a 32-bit floating-point number in IEEE 754 floating-point format . 
<triplet> Fast inverse square root <subj> reciprocal <obj> computes solution to