On 28 July 2010 04:20, Kevin Ar18 <kevinar18@hotmail.com> wrote:
I am attempting to experiment with FBP - Flow Based Programming (http://www.jpaulmorrison.com/fbp/ and book: http://www.jpaulmorrison.com/fbp/book.pdf) There is something very similar in Python: http://www.kamaelia.org/MiniAxon.html Also, there are some similarities to Erlang - the share nothing memory model... and on some very broad levels, there are similarities that can be found in functional languages.
Does anyone know if there is a central resource for incompatible python memory model proposals? I know of Jython, Python-Safethread, and Mont-E. I do like the idea of MiniAxon, but let me mention a topic that has slowly been bubbling to the front of my mind for the last few months. Concurrency in the face of shared mutable state is hard. It makes it trivial to introduce bugs all over the place. Nondeterminacy related bugs are far harder to test, diagnose, and fix than anything else that I would almost mandate static verification (via optional typing, probably) of task noninterference if I was moving to a concurrent environment with shared mutable state. There might be a reasonable middle ground where, if a task attempts to violate the required static semantics, it fails dynamically. At least then, latent bugs make plenty of noise. An example for MiniAxon (as I understand it, which is not very well) would be verification that a "task" (including functions that the task calls) never closes over and yields the same mutable objects, and never mutates globally reachable objects. I wonder if you could close such tasks off with a clever subclass of the proxy object space that detects and rejects such memory model violations? With only semantics that make the program deterministic? The moral equivalent would be cooperating processes with a large global (or not) shared memory store for immutable objects, queues for communication, and the additional semantic that objects in a queue are either immutable or the queue holds their only reference. The trouble is that it is so hard to work out what immutable really means. Non-optional annotations would be not very pythonian. -- William Leslie