Tim Bray: My experience in the Wide Finder didn’t particularly make an Erlang-lover, but I sure did come to appreciate its message-interchange framework.
So is this going to be the year of message passing? I’m old enough to remember many years that were going to be the “year of LAN”. For years, people that used LANs couldn’t figure out how people that didn’t have them could do without. Then LANs broke out and everybody did have them. And before long, nobody could figure out how they could do without. But it was years.
Will that happen with concurrent programing, and with message passing based concurrency in particular? Or will it always be a niche for the somewhat crazy?
It does seem like once you start, it’s a bit hard to image going back. You might not need to go hog wild and create a telco switch with tens of thousands of processes every day but once you have easy concurrency, you find lots of little uses for it, where you had rather annoying non-concurrent code in the past.
That is, that’s true for some definition of easy concurrency. There’s the rub. How much harder does writing concurrent programs have to be? Can we make it not harder at all? Or only a little harder? Because if we can’t, I doubt it ever will break out. That despite the dreams of all the multicore CPU vendors.
I’m optimistic, but there are a lot of degrees of freedom when it comes to deciding how to implement concurrency, even in message passing systems. So it seems unlikely that the same “right” approach is going to be obvious to everyone. I don’t how this will evolve, just the thought that the paradox of choice (not to mention FUD) is likely to keep a lot of people from even experimenting until things are a bit better understood.
One thing that seems a lot less debatable is tools. The tools we have for debugging concurrent programs … well, they pretty much suck. Prints and stack traces (which, in a concurrent world virtually always end up in the scheduler) are significantly less useful than they are in non-concurrent programs. Though it seems we want them, we seem to have not spent as much time on building them. And till we do …
So I have big doubts about this year being the year of message passing. Or even next. Etc. But just like it was with LANs, it doesn’t keep me from having plenty of fun with concurrency while I wait to surf the wave that I do think, everything above notwithstanding, is inevitable.
Tags: actors, erlang, message passing
April 28th, 2008 at 7:35 pm
Steve, how far reaching is your experience with concurrency. Dramatis is the public outing of your approach to Actors for concurrency but I bet you have used plenty of other approaches.
What other approaches have you used? I imagine several don’t even require message-passing semantics.
Have you tried transactional memory? Futures? Plain old mutexes & semaphores?
You clearly have a lot of experience here; how about a post comparing/contrasting the different mechanisms you have used before and the outcome.