Is there a fast C or C++ standard library function for double precision inverse square root?

Question

I find myself typing

double foo=1.0/sqrt(...);

a lot, and I\'ve heard that modern processors have built-in inverse square root opcodes.

Answer 1

why not try this? #define INSQRT(x) (1.0/sqrt(x))

Its just as fast, requires less typing(makes you feel like its a function), uses double precision, as accurate as 1/sqrt(..)