The PyTorch version is using the GPU (with Metal Performance Shaders); this C version is currently using (in the docs I saw) a single CPU core, with AMX (via Apple Accelerate BLAS) but not yet with OpenMP for parallelism. It’s not slow because LLM code is bad, but because it’s not running on the same hardware. That said, it’s also not as fast as it is because of the LLM—all the critical code is in kernel libraries it calls (the same as for PyTorch).