[eslaught]

HIP is basically CUDA with s/cuda/hip/g.

My experience is that the stack is pretty rough around the edges. But when it works, you (almost) literally find-and-replace, and it pretty much works as advertised. However, just because you can get to a correct code doesn't necessarily mean that code will achieve optimal performance (without further tuning, of course).

[latchkey]

Not only tuning the code, but also the bazillion knobs on the GPUs themselves.

[gh02t]

That's the upside of a supercomputer though, fixed architecture to target with enough weight that it's worthwhile.