In the past I'd tried to follow Dan's posts regarding the research being done in parrot concurrency (before the whole Leo/Dan explosion) and I hadn't really revisited the topic to check the progress being made.

What I liked in the PDD:

• first-class support for multiple thread paradigms?
• excellent depth in the GC-under-concurrency topic
• reality-based discussion of COW and VM/ints/threads
• copy constructs base on macros mapping to efficient per-OS code
• they're not throwing in too many language-specific assumptions
• continuation<=>VM mapping looks appropriate

To my limited experience, that all sounds well-reasoned. The perl6 Concurrency DRAFT spec seems quite thin on detail at this moment... is that not where this discussion should be focussed? To me it seems as though a wide variety of concurrency paradigms could be efficiently implemented based on the primitives and HLL concepts defined in the PDD.

Perhaps other monks have some ideas about what specifically could not be efficiently supported (or implemented without hazard) based on the HLL constructs in the PDD. Personally, I have two observations on the perl6 DRAFT spec:

1) I'm concerned that the language (and perhaps semantics) of the DRAFT spec are defined in terms of STM concepts.

I certainly don't discount STM as a good programming model (provided undo/redo hooks and some sort of module-boundry "contracts" for the sake of composability are provided); the concern I have is that language concurrency patterns (wrt: composability) are still in their infancy and I wonder whether one can efficiently model other concurrency paradigms on top of STM constructs.

2) Is perl6 going to be written off as unusable (by under-sold users of other languages) if it doesn't at least expose POSIX-like shared everything APIs?

I personally prefer a share/copy-nothing-by-default approach but can understand how shared-everything is very appealing to some folk. After all if parrot supports it, shouldn't perl6 at least expose it for completeness-sake?

-David

Threading is absolutely critical to Perl 6 and other languages that will run on Parrot.

That single sentence is the best news regarding Parrot I have seen written down in the last 3 years.

We have a prototype implementation,

Is this a part of the parrot distribution? Otherwise, it the prototype available for download?

Not Quite Perl is part of Parrot, and covered here on the Pugs blog. There's also v6 at CPAN; Pugs, which is written in Haskell; and KindaPerl6 (which should have a real page, but I didn't find one).

I take that to mean, that despite the context and the second half of the sentence, the "prototype" mentioned is some kind of Perl 6 language prototype, and not any kind of Parrot threading prototype.

That leaves just the existing PPD, which hasn't changed since it was drafted; is based upon the Perl 5 iThreads model; was written by people who had never used that model; makes no concessions to the obvious failures of the only existing implementation of that model; seeks to perpectuate all the mal-features of that model; and will have to be tacked-on to the Parrot single tasking architecture after the fact just as the existing implementation was.

Oh dear.

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

-moved-