How so? One of the ROCm layers is opencl which does runtime target compilation, and there is also the various intermediate language representations. So, presum

How so? One of the ROCm layers is opencl which does runtime target compilation, and there is also the various intermediate language representations. So, presumably much of this is just lack of sufficient resources to assure that all the different combinations are optimally being compiled down on all the independent HW devices. This was always the OpenCL problem too back before everyone just started using CUDA rather than trying to use it. It worked in a lot of places but the higher level code needed to be adjusted for individual devices because each vendor would do a reasonable job maintaining optimal code generation for their target given code optimized for their target, but switching vendors (AMD<->nvidia) would result in needing two different versions of the code tuned for the individual vendors ideas of how code should be tuned for their platform. If that wasn't clear say you wrote and optimized code for vendor A's device X, when vendor A released device Y, things tended to work well, but moving that code to vendor B's devices basically required retuning/rewritting things.