[falconroar]

I don't understand why developers of PyTorch and similar don't use OpenCL. Open standard, runs everywhere, similar performance - what's the downside??

[pama]

I don’t know for sure why the early pytorch team picked it, but my guess is due to simplicity and performance. NVidia optimizes CUDA better that OpenCL and provides tons of useful performance tuning tools. It is hard to match the CUDA performance with OpenCL even on the same NVidia GPU hardware, and making performant code compatible across different GPU with OpenCL is also hard. I know examples of scientific codes that became simpler and faster (on nvidia hardware) by going from openCL to CUDA but haven’t yet heard of examples the other way around.