As far as I know, Dask is at its core a tasking model (i.e. tasks have input and outputs, and run automatically when inputs are ready in a dataflow-like model).

As far as I know, Dask is at its core a tasking model (i.e. tasks have input and outputs, and run automatically when inputs are ready in a dataflow-like model). Charm++ (on which CharmPy is based) is an actor model. Think Erlang for HPC. You've got a set of objects that are all nominally running concurrently, and objects can send messages to one another. Personally, I prefer the task-based model (but of course I'm biased since I work on one myself). In a proper task-based model, you can't have races or deadlocks, everything looks to a first approximation to be sequential. In actor models there's pretty much no way to hide the conncurrency, and all the traditional pitfalls of parallel programming are exposed to the user.