> One controversial aspect of the original decoupled look-back algorithm is that it depends a forward progress guarantee from the GPU Apple GPUs aren't very am

> One controversial aspect of the original decoupled look-back algorithm is that it depends a forward progress guarantee from the GPU Apple GPUs aren't very amenable to implementing recursion or giving forward progress guarantees within a SIMD group by design. I'll have to check if a device-wide barrier type even exists on that TBDR... It isn't like NVIDIA hardware (since Volta) where you have a separate instruction pointer for each (SIMT-but-not-quite) thread.