Feature Request: minmax, position min/max, product, and sum

[okaneco]

Thanks for working on this.

There are two other function families that I find myself re-implementing a lot that I'd like to suggest as additions to the library.

minmax and more positions

• minmax_simd
• position_max_simd, position_min_simd, position_minmax_simd

It'd be nice to have these done in a single pass and without needing to successively call max/min then position.

Product and sum

• product_simd, sum_simd

These are mainly for floating point numbers. Since floating point math isn't associative, if you call product/sum then you'll get scalarized operations. You have to use your own accumulators to get vectorized operations, otherwise the slice is operated on sequentially.

If product and sum are added, it should be noted in the documentation that the results will likely not be equal to .product::<float()/.sum::<float>().

[LaihoE]

Thanks, minmax_simd, position_max_simd, position_min_simd, position_minmax_simd all seem very reasonable and will be adding them soon.

Originally I checked "product" and "sum" with i32's and the generated code was autovectorized and completely forgot about floats. The main question is how to communicate the float behaviour. I feel like mentioning it in the docs may not be quite enough... but idk. Maybe as an optional feature?

[okaneco]

Making it an opt-in optional feature makes sense to reduce unexpected/unwanted behavior for users.

I don't have any great suggestions for names, float_extras perhaps? Not particularly concerned about this.

In nightly, they've landed intrinsics which allow for behavior similar to fast-math flags for floats and labeled them f[op]_algebraic but that's subject to change. There's no short and simple way to describe these operations unfortunately.
https://doc.rust-lang.org/1.79.0/std/index.html?search=algebraic