

Fast Inverse Square Root - WhiteDawn
https://en.wikipedia.org/wiki/Fast_inverse_square_root

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ColinWright
OK, one very last time. Here are a few previous submissions of this, some of
which have comment:

[https://news.ycombinator.com/item?id=213056](https://news.ycombinator.com/item?id=213056)
: Some comments

[https://news.ycombinator.com/item?id=419166](https://news.ycombinator.com/item?id=419166)
: Some comments

[https://news.ycombinator.com/item?id=573912](https://news.ycombinator.com/item?id=573912)

[https://news.ycombinator.com/item?id=1599635](https://news.ycombinator.com/item?id=1599635)

[https://news.ycombinator.com/item?id=2332793](https://news.ycombinator.com/item?id=2332793)
: Some comments

[https://news.ycombinator.com/item?id=3115168](https://news.ycombinator.com/item?id=3115168)
: Some comments

[https://news.ycombinator.com/item?id=3259199](https://news.ycombinator.com/item?id=3259199)

[https://news.ycombinator.com/item?id=4526609](https://news.ycombinator.com/item?id=4526609)
: Some comments

[https://news.ycombinator.com/item?id=4836589](https://news.ycombinator.com/item?id=4836589)

[https://news.ycombinator.com/item?id=6106627](https://news.ycombinator.com/item?id=6106627)

[https://news.ycombinator.com/item?id=7277215](https://news.ycombinator.com/item?id=7277215)

[https://news.ycombinator.com/item?id=7297582](https://news.ycombinator.com/item?id=7297582)

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hehaho
For a second I was expecting this to be an April Fool's post about a "fast"
way to calculate the inverse of the square root function, i.e. x*x :-)

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jtlien1
A lot of times, the code you are writing does distance comparisons to
determine overlap or intersection. But if all you are doing is this, then you
can use the square of the distance which is just x^2 + y^2 and you have no
need for a square root. Some mathematicians call this "quadrance". Or just do
all your work in this metric and reserve the square rooting for when it is
absolutely necessary.

