That’s kind of the make-or-break plan for Frontier and El Capitan [1]. They’re having all the science folks try using ROCm and the HIP recompiler thing. We’ll see how that shakes out in practice.
LLNL writes their own stack usually, I don't see the main API for El Capitan being anything but OpenMP and LLNL can and has written their own compilers and libraries for other GPU powered supercomputers.
Sure, but other folks have to make use of it, too. Not everyone's code will be abstracted from CUDA. They're trying to get folks on Summit to test out HIP more strongly. Repeating my comment from last summer [1] that linked to the "try to use HIP" [2]:
> The OLCF plans to make HIP available on Summit so that users can begin using it prior to its availability on Frontier. HIP is a C++ runtime API that allows developers to write portable code to run on AMD and NVIDIA GPUs. It is essentially a wrapper that uses the underlying CUDA or ROCm platform that is installed on a system. The API is very similar to CUDA so transitioning existing codes from CUDA to HIP should be fairly straightforward in most cases. In addition, HIP provides porting tools which can be used to help port CUDA codes to the HIP layer, with no loss of performance as compared to the original CUDA application. HIP is not intended to be a drop-in replacement for CUDA, and developers should expect to do some manual coding and performance tuning work to complete the port.