Plain Threads are the GOTO of todays computing [video]

https://www.youtube.com/watch?v=4OCUEgSNIAY

by adamnemecek • 11 years ago

41 13 11 years ago

_yosefk2• 11 years ago

Actually, plain threads indeed are pretty much the goto's of parallel computing, one difference being that while various techniques analogous to "structured programming" - "structured threading", if you like - are available, they all work for some systems better than others, and often aren't very portable/ubiquitous yet. So right now they can't almost-kill raw threads the way ifs, fors and whiles almost killed goto's.

fmstephe3• 11 years ago

I think this is a really important observation.

There was a very interesting discussion between Cliff Click and Rich Hickey (linked at bottom). The highlight of it for me was Cliff Click suggesting that people often assume that because we use a range of great abstractions every day, garbage collection was his example of a very successful abstraction, there is tendency among programmers to assume that all abstractions are great. Cliff Click gives the example of a MPI as an abstraction which proved powerful in some domains but very fragile in general.

As far as I can tell we are still looking for a really good abstraction to replace threads.

http://www.azulsystems.com/blog/cliff/2008-05-27-clojure-stm...

_yosefk2• 11 years ago

Personally I'd probably label MPI as "too low-level" an abstraction, not unlike threads; and I think there are many great high-level threading abstractions which I wouldn't call fragile, from Cilk/TBB and the like to transactional memory.

What I meant to say was, Cilk/similar can be very useful at times, transactional memory at other times, Erlang-style fully isolated lightweight processes at still other times, etc. - and none of these approaches comes with a universally available interface, also none is universally taught (while threads are.)

So my guess is that raw threads will be used increasingly less but (A) it will take time and (B) either we miss something right now or it will take more mechanisms and approaches to replace raw threads than it took to replace goto.

That said, anyone needing to do something with threads today at any sort of scale (even if it's one guy who writes something that needs to be maintained over a long span of time) should IMO hide the threads behind something. (My take on it is https://github.com/yosefk/checkedthreads)

jeffdavis• 11 years ago

"garbage collection was his example of a very successful abstraction...we are still looking for a really good abstraction to replace threads"

Isolated preemptible processes are a more successful abstraction than GC or threads. Why are threads the comparison point for concurrent abstractions?

rubiquity2• 11 years ago

I like to think exceptions are also a slightly less egregious form of the GOTO.

jeorgun• 11 years ago

Many things are — http://repository.readscheme.org/ftp/papers/ai-lab-pubs/AIM-...

MetaCosm2• 11 years ago

I am a bit confused, what is the relevance of that paper to the comment? Unless I misunderstood, the comment appeared to be about flow control issues of exceptions(hidden control flow and corrupt state), and I don't see that addressed in that paper.

Dylan168072• 11 years ago

I don't really agree there. Exceptions can only break out. They're a moderately stronger form of return. You can't create spaghetti control flow with exceptions.

MetaCosm2• 11 years ago

Read this: http://www.lighterra.com/papers/exceptionsharmful/

There is a reason exceptions are often banned from environments and it isn't because they are awesome. They make code "exceptionally" (zing) hard to reason about.

Plain Threads are the GOTO of todays computing [video]

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