Ugh. At least when everyone was doing threads you only had to learn one model. Then everyone had to build a better mousetrap.
One of my pet ideas is just to implement a Go-like CSP with plain pthreads. Channels could be pipes of pointers. Channel select is just select(). No weird M:N runtime needed. I don't want an operating system in my programming language.
This is just stolen from Programming in Lua chapter 30 -- threads and states ( https://www.lua.org/pil/ , not in the 1st online edition unfortunately)
Lua has coroutines within the interpreter, but to utilize all the cores he suggests layering threads and multiple Lua interpreters on top.
Please do it! I feel like we've forgotten the lessons of NPTL, when everyone tried M:N and collectively came to a consensus that M:N wasn't worth it in practice.
It's very compatible with bash so I think it has a chance of being adopted. And I would like to add structured data pipelines, which powershell has. I was thinking of implementing it with the threads and pipes of pointers scheme (and probably the condition variable).
I guess the shell concurrency model is more like a subset of CSP, but the more general CSP model seems useful and fairly easily implementable. I feel like it should be like 200 lines of code, so I should try it sooner rather than later. Just start porting some simple Go programs to it.
( My last post about parsing expressions got buried on HN but I think it is fairly interesting to a specialized audience: http://www.oilshell.org/blog/2016/11/01.html )
If you open source the project, I'd love to try giving you a hand. Anyway, good luck with the project!
I'm rounding the corner on parsing hundreds of thousands of lines of bash scripts now... the prototype is in Python as mentioned in the first post, and the executor isn't complete, but if you want the parse-before-execution, that is working well.
ShellCheck does exist though. IIRC I had mixed experience with it -- it did actually find one bug, but on the other hand it spewed hundreds of warnings about double quoting vars, which is technically true, but not the best use of time for most scripts I write. I'd rather just get rid of stupid quoting rules, which is one of the #1 priorities.
(As far as writing, I find that "omit needless words" from Strunk & White goes a long way. Words like "very" and "a little" somehow spray themselves all over my writing; they are rarely useful and I kill them on editing passes :) )
IMHO unbuffered channels are one of the most powerful constructs in Go, since they guarantee that "resources" are always on one-side of the channel and are taken care of, and never stored in a channel (or promise, ...) where they could get abondoned/lost. It also allows to make some other assumptions like "the in-memory server has taken my request through a channel and is now working on it and will answer through a chnanel soon" or "the server has shut down so I can't write to the channel", but never "the write to the channel succeeded but nobody cares about it".
Easy. Just implement them with a mutex and a condvar. If you want, layer some lock free algorithm on top for the fast path.
The unbuffered channel would be a good reason to use that scheme. I was thinking of using pipes so Go's select reduces to the select() system call. But I think you can just do both -- it's cheap. Write to a pipe and and notify a condition variable. I'll experiment with it.
The more important difference is what kind of synchronization primitives are provided to you by the platform. Go's (synchronous) channels in combination with select provide a quite powerful tool compared to using only pthreads. Even the old WinApi with WaitForMultipleObjects and that stuff will result in other ways or solving typical concurrency problems.
The problem of threads vs async in C seems pretty well studied, but a more interesting question is what we're talking about here: concurrency models in higher level languages: async/await in JavaScript vs. threads in JavaScript. Or let's say Python, because it actually has threads.
I feel like that tradeoff has been less well studied. Interpreters probably use a lot more stack space than native programs, but I wonder if anyone has quantified it.
And on the other hand, the downside of async is less pronounced than in C -- the whole point is to avoid "stack ripping" and explicit state machines.
And I have to echo the recent post here about the complexity of the async/await mechanisms in Python, although honestly I'm not that well-versed in the model.
https://news.ycombinator.com/item?id=12829759
(Interesting that the top comment there is kind of echoing our issue with M:N threading -- the inner platform effect.)
Green threads shine because they take ~1kB without tweaking. That means you just pack your software, send elsewhere, and you get those millions of threads per server, instead of losing hours on customer support, and have it revert to 10k threads at random because of bad sysadmins.
Anyway, "thread" is not really a concurrency oriented concept. It mixes so much of parallelism that it's expected that it has some downsides compared o purely concurrent concepts.
musl is interesting though. I've never seen it pitched as a solution for normal machines. I've always seen it in the context of small embedded systems.
Now when targeting bare metal deployments like unikernels, it is a different story in how to approach it.
They are really not comparable to threads.
For example, transferables let you move bulk data between threads without cloning. At least that removes most of the communication overhead. https://developer.mozilla.org/en-US/docs/Web/API/Transferabl...
On firefox you can transfer your WebGL canvas to a Web Worker, how is that for useful? https://hacks.mozilla.org/2016/01/webgl-off-the-main-thread/
You can use Web Sockets in Web Workers in very recent Firefox (48+?) and Chrome versions. https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers... And you've always been able to do AJAXy things on Web Workers as well.
I'm not saying the API's are clean or lovely, but the multithreaded functionality is there for the taking.
38+. It's been shipping for a year and a half.
Good to know it's stable for awhile, thanks for the update. Go Mozilla, go!!
I'm not sure what you mean that web sockets aren't supported since the MDN shows it as being fully available:
https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers...
Where this falls down is in handling events where some actions inherently need to be synchronous (preventDefault, stopPropagation), however I think Angular 2 was starting to consider options on how to overcome that. I can't speak for progress in other frameworks.
You can also do XMLHttpRequest and fetch in web workers. And IndexedDB, so you can store stuff persistently from a worker and then read it back from a worker later.
I agree that if you want to hand out data on the client to a worker pool after getting all the data from somewhere in the main page script, then serialization/deserialization can start to bite.