For those discussing it, ORNL explicitly calls out the need to rewrite and retune in the CUDA => HIP transition on Page 3 of the spec sheet [1].<p>Edit: I assume getting folks to test on Summit is a big part of the de-risking plan.<p>> 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.<p>[1] <a href="https://www.olcf.ornl.gov/wp-content/uploads/2019/05/frontier_specsheet.pdf" rel="nofollow">https://www.olcf.ornl.gov/wp-content/uploads/2019/05/frontie...</a>