7 ms·
Channels, Concurrency, Cores: A New Concurrent ML Implementation (2017) [video]
- sctb 8y agoDiscussions on Andy's related blog posts: https://news.ycombinator.com/item?id=14664150 https://news.ycombinator.com/item?id=14664150 https://news.ycombinator.com/item?id=17083447 https://news.ycombinator.com/item?id=17083447
- bjoli 8y agoNot only that, but guile just got a 2-4x speedup in the 2.9 branch (what will become guile 3). It is a really nice scheme implementation and very capable. The stuff the guix people have done is amazing! Concurrent ML is my favourite way of writing multi threaded parallel programs. It is a bliss! One can say that reagents in multidirectional ocaml is another step downwards in that it in most regards generalises CNL, but in its base form it is not as simple to work with. Guile fibers is amazing to work with, and has good repl integration. The performance I am able to get out of it is nothing short of amazing.
- dman 8y agoWhat are you using it for? Is any of the work publicly available?
- bjoli 8y agoI have started using it to do every single task that I would previously use threads for, and for a lot of other things that I would otherwise have done sequentially. Two days ago I made my own very shitty static site generator parallel using fibers. I have a POC for a irc-like server with proof-of-work to send messages depending on current message throughput. (Not online yet) I am not really a programmer, so I mostly do stupid things with it. I made my smart home server (written by me, using ZigBee to communicate with devices) scale to thousands of parallel authenticated connections. Just for fun (or at least to be able to say that my WiFi and ZigBee dongle gave up before my own ZigBee controller software did). I have even used it for fully cooperative multitasking (by setting the "Hz" in guile-fibers to 0).
- jacinabox 8y agoI just want to say that I'm so glad people are developing concurrent languages. The day that concurrency became of paramount importance to computing, all of the old languages became obsolete! That's also why we have Go; goroutines are a major innovation upon threads.
- bjoli 8y agoHow does go select over N channels where N is not known at compile time these days? I remember the helper API as clumsy and unintuitive. I am sure this has changed since I last used go. Back then (about 2014?) I found go's concurrency model lacking, or at least a little bit too opinionated when compared to CML. Sure, it was possible to work around the limitation, and the extra performance you got from utilising all cores was worth it (parallel CML is a rather new thing, but is getting more common.).
- cdoxsey 8y agoHere's one way: func fanin(out chan<- int, ins ...chan int) { switch len(ins) { case 0: case 1: for msg := range ins[0] { out <- msg } case 2: for { var msg int select { case msg = <-ins[0]: case msg = <-ins[1]: } out <- msg } default: go fanin(out, ins[:len(ins)/2]...) go fanin(out, ins[len(ins)/2:]...) } } https://play.golang.org/p/9KNkheXHUBr https://play.golang.org/p/9KNkheXHUBr You can also use reflect: https://golang.org/pkg/reflect/#Select https://golang.org/pkg/reflect/#Select
- pjmlp 8y agoModula-2 already had co-routines in 1978. Concurrent Pascal had them in 1976. And there are plenty of other examples gaining digital dust.
- bakul 8y agoConcurrent pascal didn't allow unsafe concurrent access to shared data structures. Go allows safe concurrent access but doesn't stop such access. Its authors encourage people to use channels but this sharing is intrinsic -- one can start a nested function as a concurrent goroutine & it has full concurrent access to its environment. Go tools can check for race conditions but ideally such support should be in the language itself. So in a sense Go is worse than Concurrent Pascal for the main feature it touts!
- a-nikolaev 8y agoThe speaker's article on the topic: https://wingolog.org/archives/2017/06/29/a-new-concurrent-ml https://wingolog.org/archives/2017/06/29/a-new-concurrent-ml
- jules 8y agoHow does this compare to Reagents? If I understand correctly, Reagents are the successor of Concurrent ML. http://kcsrk.info/ocaml/multicore/2016/06/11/lock-free/ http://kcsrk.info/ocaml/multicore/2016/06/11/lock-free/
- bjoli 8y agoReagents generalise CML, but is also not as opinionated in that it is more a set of building blocks that can be used in many different ways. It gives you more flexibility, but at the cost of having to do a bit more yourself. Reagents are more comparable to STM I would say, even though it is slightly less expressive in some areas, but on the other hand is always lock-free.
- jules 8y agoApparently I also answered my own question a year ago as a comment on the associated blog post: Reagents do generalise CML. The main difference is that CML only allows you to combine operations with select (op1 OR op2) while Reagents also allow you to combine operations into a transaction (op1 AND op2 for independent operations and op1 THEN op2 for dependent ones). Reagents are lightweight in that the library analyses the combined operation and then figures out an efficient CAS scheme to execute it. Reagents also include some more low level operations, such as CAS as a reagent. -- https://wingolog.org/archives/2017/06/29/a-new-concurrent-ml#e65f4a9c7419cf15c71a58df4786a1a15f8066e9 https://wingolog.org/archives/2017/06/29/a-new-concurrent-ml... I hope that's correct... > Reagents are more comparable to STM I would say, even though it is slightly less expressive in some areas, but on the other hand is always lock-free. What is the difference in expressiveness between STM and Reagents? Is it that STM provides monadic bind, whereas Reagents only provide applicative, i.e. Reagents cannot dynamically decide to update different locations based on values read in the transaction?
- bjoli 8y agoWell, after having used reagents I have found that for most things so use it to more or less implement CML anyway. I have never been limited by the CML way, but I do appreciate the power that reagents give you. In comparing STM and reagents I will probably just regurgitate what Aaron Turin says in his paper "Reagents: Expressing and Composing Fine-grained Concurrency" which you can find using a short Google. I only seem to be able to copy the Google link, so you will have to Google it yourself.