> I live only in CUDA land, I’m a bit ignorant of the other platforms, so I’m not sure what granularity of workgroups is here. Generally speaking you can’t rely

> I live only in CUDA land, I’m a bit ignorant of the other platforms, so I’m not sure what granularity of workgroups is here. Generally speaking you can’t rely on individual threads executing in any particular order, no matter how many there are, so yes you can’t have one thread look at data from another thread without some kind of synchronization https://news.ycombinator.com/item?id=29257343 https://news.ycombinator.com/item?id=29257343 The only thing Raph relies on is, that if and only if a thread ever starts to run, then it will continue to make progress until it completes. This is something you can rely on, e.g., on NVIDIA GPUs since Turing/Volta, and allows you to use atomics, barriers, semaphores, etc.