The place of Concurrency (in c++)

[Ruth Ivimey-Cook <ruth@xxxxxxxxxx>]

Folks,

I have just become aware (shame on me!) of some really excellent video 
talks by Herb Sutter on the website http://cppandbeyond.com, including 
this one talking about Concurrency:
http://channel9.msdn.com/Shows/Going+Deep/C-and-Beyond-2012-Herb-Sutter-Concurrency-and-Parallelism

It is somewhat long, but IMO it's worth thinking about.

In one sense I am glad C++ is moving beyond mutexes at last, but I kept 
wanting to ask about the CSP concepts. Near the start of the talk Herb 
introduces a log writer, comparing a mutex implementation to a queues 
based one. The queues based one (i.e. send() a message to a worker 
thread) was presented as if it was forever committed to being 
asynchronous, while a simple receive() of an ack would have enabled 
synchronous action. In the talk as a whole, "blocking == bad", which in 
one respect is a good thing, but it's also a dangerous thing to run away 
with, I think. Blocking is bad in the extreme, but it's essential sometimes.

Herb also talked about using "futures" - result-variables used to access 
an async value - and the possibility of avoiding a wait() on the future 
value by using "then()" actions to append another function to the 
existing thread.

It all seems so horribly messy and - to say the least - the syntax is 
getting worse than perl 4.

Is there anything we as a community can do to inject another viewpoint 
into this debate? Herb and his colleagues are no doubt very respected 
and very intelligent people, and yet they (and the rest of the C++ 
standards board) seem to be making such an awful mess of what should be 
such a simple idiom.

... or is it me that is missing the plot?

The good thing about this is that people are talking about the issues, 
are aware of things like deadlock, and are no longer head-in-sand about 
it. And that things are changing, both in the standards and elsewhere. 
And therein lies an opportunity.

Regards
Ruth

--
Software Manager & Engineer
Tel: 01223 414180
Blog: http://www.ivimey.org/blog
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