> Modern CUDA uses explicit programmer-managed masks, which is powerful and takes advantage of their hardware specifics. But mis-using the mask can cause a deadlock, as divergent threads could simply never participate in a subgroup operation that expects them to, leaving the other threads to block forever. I can see why this solution leaves to be desired, as it just offloads the problem and the risk of misuse to the user.

Note, on Volta (2017, present on customer since Turing in 2018) onwards, Independent Thread Scheduling is present, with a separate instruction pointer per SIMT thread.

This allows to have atomics across different lanes of the same warp, as such providing the guarantees assumed by the C++ memory model. Quite some modern CUDA apps are starting to rely on that, and as such will not work on Pascal or earlier, nevermind other GPU vendors.

Cooperative Groups are very flexible in CUDA too.

https://docs.nvidia.com/cuda/volta-tuning-guide/index.html#s...

As such, control flow is handled very differently on post-Volta GPUs compared to pre-Volta ones, with pre-Volta more akin to what AMD still does today.