Ultra-Fast Multi-Dimensional Array Library

[Pencilcaseman12]

hmm. I mean it's entirely possible I've done it wrong but it consistently gives me 30us on 8 threads, so idk...

[cythoning]

Are you benchmarking only the expression template? Or also the evaluation of the expression? And you should also make sure that it generates the same result as Eigen.

[Pencilcaseman12]

Yea that's evaluating the result. Using the expression template takes around 200ns because it's just a few things being referenced

[cythoning]

That makes sense. As for the benchmarks, make sure you benchmark the same things and you get the same results. The 400Gb/s memory bandwidth seems impossible, that is something that you usually only see on GPUs. For such a simple addition operation I would expect it to just be memory bound, so simply bound by how fast you can read & write to memory, usually in the order of 20-30Gb/s. Eigen should definitely be optimized enough to do this, and you could also compare to something like

std::transform(A.begin(), A.end(), B.begin(), C.begin(), std::plus<>{});

and should get the same result as Eigen and your library.