Fast inverse square root · shard-db HN Explorer

I tried implementing it in JS just for fun. I don't get how/why it works, but it does.

Is your implementation correct? I get strange values.

    Q_rsqrt(16) = 0.24957678739619552

I'm not sure if I'm just not doing something correctly. Even if I go to a smaller number I get:

    Q_rsqrt(0.125) = 2.828426859705843

Which is vastly off (10x ish)

More accurate numbers are

  0.25

and

  2.8284271247461900976033774484194

respectively.

You can compare it to the native implementation here. Looks okay, if a little inaccurate to me: http://codepen.io/anon/pen/KavzKK

Fast inverse square root (en.wikipedia.org)