Arthur wrote: > > > >>> -----Original Message----- >>> From: Laura Creighton [mailto:[EMAIL PROTECTED] >>> > > >>> And I think he will like tens of thousands of threads, too, >>> though if these just means tens of thousands of chances to >>> modify only part of your complex number, when you wanted an >>> atomic action guaranteed to modify both parts as one, then >>> he may hate it before he likes it. :-) >>> > > Sorry - I suspect everyone else is quite done with this, but I'm still > bothered by mixed signals. > > I would like to be able to present PyGeo as good, sensible code. Not Museum > Quality, to be sure. But good and responsible. > > There is an implication in what you are saying that I am still off the mark. > Perhaps I am. But its not fair, in my mind, to throw that at me knowing > that it still has not gotten through to me (and Zelle ?) in what way I am > off the mark. > > For the life of me I don't see the problem. My class has 2 __slots__ - > .real and .imag. It does with them the kind of things that classes do. > > How is this class different and less thread safe than an infinite number of > other classes that do with attributes the kinds of things that classes do > with attributes? > This is a complex matter and I'll try to give a very short (hence a little categoric) answer. First of all, IMO Laura was referring to several thousands of lightweight thread such as those found in the Oz/Mozart language (http://www.mozart-oz.org). And that is because we have had a PyPy/Oz sprint two weeks ago where we made plans and prototypes for the integration of some ideas of Mozart into PyPy (mostly logic variables, "search", and constraint programming, micro-threads were already on the go).
In that language stateful datatypes such as mutable objects are an exception. By default the variable store is a single assignment store. That means when you create a variable (e.g. with this statement X=_ ) it is uninitialized (called unbound). Then when you assign it you cannot rebind it to an other value: X=4 works but if you do X=5 later you get a sort of exception (failure). In a sense = does not do assignment but true mathematical equality (called unification). So you can do 4=X as well as 1+X = 5. The language supports very lightweight threads (having a million of those is no problem), when they try to "use" the value of a variable , they block if the variable is unbound. So you can launch inter-dependant threads accessing values computed by each others without wondering about the synchronization. That is called dataflow concurrency. In a sense, your mutable complex object is opposite to that approach where (almost) all variables never ever change their value. > I have unintentionally stimulated a CS nerve, apparently. But would still > love to get to the bottom of issue. > HTH :-) > Or get an official CS - proper use case aside - bill of health. > I would refer you to the CTM book: http://www2.info.ucl.ac.be/people/PVR/book.html You will find there lots of interresting ideas about computer language semantics. Best, -- Grégoire Dooms _______________________________________________ Edu-sig mailing list Edu-sig@python.org http://mail.python.org/mailman/listinfo/edu-sig
