Bits and Pieces
This has been a pretty content-free zone lately. Most of that has been due to work pressure. I've got a few systems going live around now and, as always, the last 20% of each project takes 80% of the time. Anyway, I have been looking at a few things here and there that might be of interest...
First off, I noticed that George Chrysanthakopoulos has announced on the MSRS CCR forum that work is underway to unify the CCR with the PFX libraries recently released to CTP, although no time-frames have been given. Additionally, George also states that they are working towards the integration of the CCR into the core .NET libraries (possibly via PFX?). This is excellent news all round. I read with interest the MSDN article on the Task Parallel library, which sits at the core of PFX. Actually, in my line of work, I believe the CCR would be more useful than PFX, as taming the asynchrony, whilst exploiting the latent concurrency tends to be the bigger (and harder) problem than parallelising the processing of the data itself. Nevertheless, it's as a good a vehicle as any in which to ship the CCR and means that in future, if you're considering the library and don't work in robotics you won't have to try and convince your boss why buying and deploying MSRS is a good idea.
I've also been following the herd and researching F#, following the announcement that Microsoft are to fold it into the set of officially supported .NET languages. I've noted before what I liked in general about the language, but readers of this blog might be interested in what it offers in the sort of space that CCR plays in.
- Immutability. In common with many functional languages the default syntactic declaration of a 'variable' is immutable. Immutability is a generally useful property in concurrent programming and message-passing systems in particular. F# makes it simple to both declare types (records) and instances of them in a way well-suited to message-passing.
- Composition. Functional languages tend to compose and decompose solutions very well (see this classic introduction). This ability helps factor out a lot of concurrent machinery, whilst still exploiting it. In fact, Joe Armstrong called this 'Abstracting out Concurrency' in his PhD thesis, and Erlang programs, whilst naturally concurrent, tend to make heavy use of these common patterns.
- The latest version of F# contains support for 'workflows', which are very similar in concept to CCR iterators, although an entirely different implementation under the covers. Robert Pickering's blog has covered these in a recent series of tutorials, as well the Erlang-style message-passing approach (something akin to one-time CCR receivers in a read-process loop) it supports.
Incidentally, I read Robert's book, Foundations of F# as my first foray into the language. I thought the book was pretty good, but felt (as an FP novice) that it might have benefited more by explaining a little more about FP style and accumulated good practice. Anyway, since then I have also read Practical OCaml, since F# aims to be compatible with a subset of OCaml. If you're considering either, my personal recommendation would be read the OCaml book first, and then read Foundations, since the former does a better job of introducing functional programming and the latter provides solid examples of integration with the existing BCL.
I've also been working on very lightweight COM-based C++ library for Erlang-style message-passing and task distribution over the native Win32 thread-pool. It's an ATL-style solution i.e. headers only and I'll blog a little more about this in future.
