Fast Inverse Square Root

Re:Fast Inverse Square Root by recursive on Monday November 02, 2020 @05:49PM (#24974395)

Thanks for this. I have one nit. You show `q = 1598029824 - u/2;` as being identical to `q = 0x5F400000 - u >> 1;`, but every language I know of uses a different order of operations, giving different results. It might be clearest to provide parentheses in the second case.

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Re:Fast Inverse Square Root by usmannk on Monday November 02, 2020 @06:27PM (#24974682)

Interestingly enough it seems to do the shift first in Swift

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Re:Fast Inverse Square Root by TwoBit on Monday November 02, 2020 @09:47PM (#24975854)

All well-known programming languages will do the shift first.

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Re:Fast Inverse Square Root by thehobgoblin on Monday November 02, 2020 @10:24PM (#24976003)

I looked at about 20 different "popular" languages and I believe that only 2 (Go and Swift) of them have shifts at a higher precedence than addition.

I think I'm missing a reference/joke =/

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Re:Fast Inverse Square Root by hemdawgz on Tuesday November 03, 2020 @04:51AM (#24978088)

Or this might just be another confident but baseless HN commenter assertion.

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Re:Fast Inverse Square Root by copascetic on Tuesday November 03, 2020 @01:13AM (#24976871)

C, C++, Java, and Rust all have shift as lower precedence than addition/subtraction. Edit: and Javascript, Python.

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Re:Fast Inverse Square Root by recursive on Tuesday November 03, 2020 @10:29AM (#24980491)

You can add C# as well.

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Re:Fast Inverse Square Root by beached_whale on Monday November 02, 2020 @10:04PM (#24975923)

Use brackets to be explicit about your expected order of operations.

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Re:Fast Inverse Square Root by timhh on Tuesday November 03, 2020 @04:25AM (#24977943)

Oops! I added brackets, thanks!

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