TBH, I think there's some truth to that. I spent _ages_ tuning the kernels to match the tested FLOP count of my M3's processor. I only have an M3 though and wasn't able to push int8 very far on it, but I think there's a chance that M5-class machines and higher might have more capability in this regard.

What I also learned is that MLX/vLLM is probably within ~20% or so of the absolute max perf on Mac. I found some improvements over what they were doing, but we're at the point where it's challenging to optimize without per-stepping kernels.

I found a few improvements over stock DiffusionGemma along the way, like using top-k attention, which drastically improves perf on my mac without sacrificing any of the benchmarks I was able to throw at it.

FWIW some of the issues with Gemma being slow on Mac are specific choices they've made in the architecture that make it challenging to make use various optimizations that have popped up recently. I think a Kimi K3-style network hybrid with the diffusion bits of DiffusionGemma could have some serious sway.

I think that diffusion still has an edge locally, but with some architecture tweaks and CPU improvements it would actually be a winner (ie: training the network for smaller token batch sizes or flexibility in attention heads, a less expensive attention mechanism, and others).