[monocasa]

The various SIMD ISAs are different enough from eachother that you really want a custom implementation per ISA for perf reasons. Particularly if you're doing something off the beaten path like this rather than cranking through some vector math.

[celeritascelery]

I don't know. Looking in their code, they have one for SSE and another for AVX2. The algorithm is identical expect for one is 128 and the other is 256 bits. It seems like something that would be easy to abstract over so you only had a single implementation (at least for x86 SIMD). But it is obviously a hard problem or it would be solved already.

[Fronzie]

Even for vector math, there are subtle differences, such as the numerical precision of the hardware reciprocal, leading to different implementations for x/y.

The Eigen library did recently combine most SSE and AVX code paths, however: https://eigen.tuxfamily.org/index.php?title=3.4

[pgwhalen]

Can you comment on the Vector API that Java is set to include? Do you think it's entirely misguided, or more of a best effort given what one can reasonably expect from Java?

http://openjdk.java.net/jeps/8261663

(I'm completely ignorant on the subject)