This entire space has a lot of options, and it's still an open question about what is the right approach. The fact is that C++ is a scalar language, with scalar

This entire space has a lot of options, and it's still an open question about what is the right approach. The fact is that C++ is a scalar language, with scalar guarantees and scalar assumptions built into their types. Hacking around this requires sacrifices, and different libraries are choosing different approaches. EVO (not featured in your list) is trying to approach it from an algorithms point of view. Highway is portable wrappers around common functionality. I think this is inherently a language-compiler problem. When libraries are using intrinsic functions to override compiler decisions, they interact poorly. One example: here's comparing a scalar versus an avx-512 intrinsic version of accumulate. https://godbolt.org/z/cMafh4Pnv https://godbolt.org/z/cMafh4Pnv IDK if you can read assembly, but the intrinsic version is waaaay worse, and about 4x slower. This is because using intrinsics makes it very hard for the compiler to do other optimizations it otherwise would (e.g. unrolling and reordering).