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A comment on Revisiting the Fast Inverse Square Root – Is It Still Useful?. Parent comment

Re:Revisiting the Fast Inverse Square Root – Is It Still Use... by pclmulqdq on Thursday April 20, 2023 @10:45PM (#35649224)
With appropriate rounding modes, the basic operations (+, -, *) are fairly short code sequences. Things like exp and 1/x can become adventures, but they're not too bad.
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Re:Revisiting the Fast Inverse Square Root – Is It Still Use... by stephencanon on Friday April 21, 2023 @07:43PM (#35661725)
Division is actually pretty straightforward: compute a residual using the multiply-add that you already have, divide _that_, and then add it to the quotient.

Or (roughly equivalently, but maybe easier to understand) do a native double division, then do a Newton-Raphson step, which requires only multiplication and addition (just like you would refine a reciprocal estimate).

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