Fast min() of array

by Ricardo Fernández Serrata

Version 1 (July 8, 2022)

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By using loop unrolling and some kind of SIMD, the processing speed can be extremely high.

Because we're using "high-level SIMD", function calls are less frequent, which improves performance.

If you're 100% sure that the input array doesn't contain `null` you should remove the `|| out = null` check, for more speed. That's there to reduce latency when the array contains a `null` somewhere in the 1st half.


I decided to handle the remainder before the loop, because it uses less blocks and has same performance.

To handle the remainder after the loop, you must create a "fake length" variable, a var that stores the length of array floored to the nearest multiple of 8, by using any of these 3 expressions:
(the 1st is the fastest)
`#A & 0x7ffffff8`
`#A // 8 * 8`
`#A >> 3 << 3`

Generalization for any unrolling degree `e` (this flow uses e := 8):
`n & (0xffffffff << e)`
`floor((n | 0) / pow(2, e)) * pow(2, e)`
`n >>> e << e`

You would then iterate using the fake length, then do `#A - i` to calculate the remainder after the loop has ended.


I didn't include max(), because it's extremely easy to implement, there's no need to handle remainder, because max() ignores `null`

Disclaimer: The speed difference is only noticeable with bigger arrays. The example array is too small

LICENSE: https://unlicense.org