Zig's Curious Multi-Sequence for Loops

Re:Zig's Curious Multi-Sequence for Loops by cgh on Monday February 27, 2023 @04:44PM (#34962309)

How cache-friendly are zip/enumerate implementations? Zig is influenced by the ideas behind Data Oriented Design, mentioned in the article (and a buried lede, if you ask me). Explicit for loops like this are generally cache-friendly and ideal for eg game programming, as shown in the structs of arrays example.

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Re:Zig's Curious Multi-Sequence for Loops by steveklabnik on Monday February 27, 2023 @05:03PM (#34962557)

I tossed together a simple function using enumerate https://godbolt.org/z/PKsEdKvKK

You get the same exact asm as the manual loop.

Of course, the idiom recognition seems to kick in, in both cases, as there's no actual loop here. I tossed in a +sum, which makes that fail, so you get some loops, check it out:

https://godbolt.org/z/1ddf5ded7

They are one instruction different in length, which is kind of amusing to me. Some small differences.

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Re:Zig's Curious Multi-Sequence for Loops by cgh on Monday February 27, 2023 @05:33PM (#34962943)

Thanks, that’s exactly what I was asking. I don’t write Rust so it’s informative to see this.

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Re:Zig's Curious Multi-Sequence for Loops by steveklabnik on Monday February 27, 2023 @05:52PM (#34963137)

Any time.

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Re:Zig's Curious Multi-Sequence for Loops by vore on Monday February 27, 2023 @04:50PM (#34962387)

As cache-friendly as advancing two pointers and a bounds check.

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