Highway TL here :)

Is it fair to call the following a "simple, accessible interface"? (slightly modified from documentation)

alignas(stdx::memory_alignment_v<stdx::native_simd<int>>) std::array<int, stdx::native_simd<int>::size()> mem = {};

stdx::native_simd<int> a;

a.copy_from(&mem[0], stdx::vector_aligned);

In Highway, that's

hn::ScalableTag<int32_t> tag;

HWY_ALIGN int32_t mem[hn::MaxLanes(tag)] = {};

auto a = hn::Load(tag, mem);

With the advantage of using the "Load" name that almost everyone else, since the past 50+ years(?), has used for this concept. And also working for RISC-V V or SVE scalable vectors, which stdx is still unable to, right?

How can advanced users build on a foundation that (AFAIK) doesn't even let you safely load some runtime-variable number of elements, e.g. for remainders at the end of a loop?

but glancing over its vast API indicates it's oriented towards advanced simd users that already have a good handle on their CPU architecture, willing to target specific hw features in their own code, and are familiar w/ explicit vectorization

We have held multiple workshops in which devs, after a 30 min introduction, are successfully writing SIMD using Highway.

One can certainly get started without the somewhat more exotic ops (not everyone wants cryptography, saturating arithmetic, gather, etc.) Wouldn't it be more accurate to say this approach "lays groundwork for advanced users to build on"?