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How's the performance of OCaml, and what's its concurrency story? I feel like on paper, at least, OCaml ticks all the boxes on my programming language wishlist

How's the performance of OCaml, and what's its concurrency story? I feel like on paper, at least, OCaml ticks all the boxes on my programming language wishlist: non-nullability, ADTs, type inference, compiles to binary. A lot like rust but a little higher level. But I've never really had a go at it. I'm sort of reluctant to sink time in it if there's not a future, but it seems to be kind of chugging along, not really gaining or losing ground, AFAICT.

HumanDrivenDev 8y ago
As a language, it's great. As a real world environment/eco-system to get stuff soon? I've been waiting for it to get there for years, and it still hasn't. I check in every 12 months or so, am reminded how nice the language is, and quickly abandon ship when I realise how annoying it is to actually develop software.
- deleted 8y ago
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chrisseaton 8y ago
> what's its concurrency story I think concurrency is fine (threads and async are options) but parallelism still seems to always be just around the corner and never actually here. I understand part of the problem is making their GC able to handle parallel allocations without hurting basic allocation performance more than they're willing to do.
klibertp 8y ago
The concurrency story is similar to what you get in Python. On one hand, you have event loop implementations with various conveniences for scheduling callbacks (Async, LWT); on the other, you have OS-level threads, but the runtime system has a global lock which makes only one thread execute at a given time. So no parallelism without forking[1] to separate processes. Moreover, the interactions between an event loop and OS-level threads which sometimes arise are non-trivial and in my experience very hard to get right, even with the helpers in Async. Single-threaded performance is generally good when natively compiled. In a benchmark I did a few years back, which consisted of traversing the filesystem with `opendir`, `readdir` and friends, OCaml was minimally slower than C++ and Nim (when compiled natively) and around Python and Racket when byte-compiled. It probably would be even faster if I used its imperative features. Looking at the code today I also see some unnecessary copying of lists, which could be mitigated. All in all, I think OCaml has a really good performance considering its high-level semantics. You have to be aware of relative costs of operations, but if you do, "as fast as C" is certainly attainable. OCaml code for the benchmark: https://klibert.pl/posts/walkfiles-ocaml.html https://klibert.pl/posts/walkfiles-ocaml.html and the results: https://klibert.pl/statics/images/walkfiled_perf_test1.png https://klibert.pl/statics/images/walkfiled_perf_test1.png [1] Actually, I just checked and it looks that `fork` is not implemented, so copy-on-write memory sharing is impossible, even on POSIX systems. Docs: http://caml.inria.fr/pub/docs/manual-ocaml/libunix.html http://caml.inria.fr/pub/docs/manual-ocaml/libunix.html http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html
- gmfawcett 8y ago
  Re-read the page that you linked. Fork isn't implemented on Windows, where fork doesn't exist anyways. Forking works just fine in Ocaml (on Unixes). Unix module docs (with fork!): http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html

HumanDrivenDev 8y ago

As a language, it's great. As a real world environment/eco-system to get stuff soon? I've been waiting for it to get there for years, and it still hasn't. I check in every 12 months or so, am reminded how nice the language is, and quickly abandon ship when I realise how annoying it is to actually develop software.

deleted 8y ago
[deleted]

chrisseaton 8y ago

> what's its concurrency story I think concurrency is fine (threads and async are options) but parallelism still seems to always be just around the corner and never actually here. I understand part of the problem is making their GC able to handle parallel allocations without hurting basic allocation performance more than they're willing to do.

klibertp 8y ago

The concurrency story is similar to what you get in Python. On one hand, you have event loop implementations with various conveniences for scheduling callbacks (Async, LWT); on the other, you have OS-level threads, but the runtime system has a global lock which makes only one thread execute at a given time. So no parallelism without forking[1] to separate processes. Moreover, the interactions between an event loop and OS-level threads which sometimes arise are non-trivial and in my experience very hard to get right, even with the helpers in Async. Single-threaded performance is generally good when natively compiled. In a benchmark I did a few years back, which consisted of traversing the filesystem with `opendir`, `readdir` and friends, OCaml was minimally slower than C++ and Nim (when compiled natively) and around Python and Racket when byte-compiled. It probably would be even faster if I used its imperative features. Looking at the code today I also see some unnecessary copying of lists, which could be mitigated. All in all, I think OCaml has a really good performance considering its high-level semantics. You have to be aware of relative costs of operations, but if you do, "as fast as C" is certainly attainable. OCaml code for the benchmark: https://klibert.pl/posts/walkfiles-ocaml.html https://klibert.pl/posts/walkfiles-ocaml.html and the results: https://klibert.pl/statics/images/walkfiled_perf_test1.png https://klibert.pl/statics/images/walkfiled_perf_test1.png [1] Actually, I just checked and it looks that `fork` is not implemented, so copy-on-write memory sharing is impossible, even on POSIX systems. Docs: http://caml.inria.fr/pub/docs/manual-ocaml/libunix.html http://caml.inria.fr/pub/docs/manual-ocaml/libunix.html http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html

gmfawcett 8y ago
Re-read the page that you linked. Fork isn't implemented on Windows, where fork doesn't exist anyways. Forking works just fine in Ocaml (on Unixes). Unix module docs (with fork!): http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html http://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html