triple-buffer VS ocaml

Great write up! I believe the colloquial name for this algorithm is a "lock-free triple buffer". Here's an implementation in Rust (I couldn't find any c/c++ examples) that has extremely thorough comments that might help completely wrap your head around the synchronization ordering. Rust uses the same semantics for atomic primitives as C11, so it should be pretty easy to match up with your implementation. I came to the same conclusion as you to solve an issue I had with passing arbitrarily large data between two threads in an RTOS system I was working with at my day job. It was an extremely satisfying moment, realizing the index variable was sufficient to communicate all the needed information between the two threads.

Rust marks cross-thread shared memory as immutable in the general case, and allows you to define your own shared mutability constructs out of primitives like mutexes, atomics, and UnsafeCell. As a result you don't get rope to hang yourself with by default, but atomic orderings are more than enough rope to devise incorrect synchronizations (especially with more than 2 threads or memory locations). To quote an earlier post of mine:

In terms of shared-memory threading concurrency, Send and Sync, and the distinction between &T and &Mutex and &mut T, were a revelation when I first learned them. It was a principled approach to shared-memory threading, with Send/Sync banning nearly all of the confusing and buggy entangled-state codebases I've seen and continue to see in C++ (much to my frustration and exasperation), and &Mutex providing a cleaner alternative design (there's an excellent article on its design at http://cliffle.com/blog/rust-mutexes/).

My favorite simple concurrent data structure is https://docs.rs/triple_buffer/latest/triple_buffer/struct.Tr.... It beautifully demonstrates how you can achieve principled shared mutability, by defining two "handle" types (living on different threads), each carrying thread-local state (not TLS) and a pointer to shared memory, and only allowing each handle to access shared memory in a particular way. This statically prevents one thread from calling a method intended to run on another thread, or accessing fields local to another thread (since the methods and fields now live on the other handle). It also demonstrates the complexity of reasoning about lock-free algorithms (https://github.com/HadrienG2/triple-buffer/issues/14).

I find that writing C++ code the Rust way eliminates data races practically as effectively as writing Rust code upfront, but C++ makes the Rust way of thread-safe code extra work (no Mutex unless you make one yourself, and you have to simulate &(T: Sync) yourself using T const* coupled with mutable atomic/mutex fields), whereas the happy path of threaded C++ (raw non-Arc pointers to shared mutable memory) leads to pervasive data races caused by missing or incorrect mutex locking or atomic synchronization.

In terms of shared-memory threading concurrency, Send and Sync, and the distinction between &T and &Mutex and &mut T, were a revelation when I first learned them. It was a principled approach to shared-memory threading, with Send/Sync banning nearly all of the confusing and buggy entangled-state codebases I've seen and continue to see in C++ (much to my frustration and exasperation), and &Mutex providing a cleaner alternative design (there's an excellent article on its design at http://cliffle.com/blog/rust-mutexes/).

My favorite simple concurrent data structure is https://docs.rs/triple_buffer/latest/triple_buffer/struct.Tr.... It beautifully demonstrates how you can achieve principled shared mutability, by defining two "handle" types (living on different threads), each carrying thread-local state (not TLS) and a pointer to shared memory, and only allowing each handle to access shared memory in a particular way. This statically prevents one thread from calling a method intended to run on another thread, or accessing fields local to another thread (since the methods and fields now live on the other handle). It also demonstrates the complexity of reasoning about lock-free algorithms (https://github.com/HadrienG2/triple-buffer/issues/14).

I suppose &/&mut is also a safeguard against event-loop and reentrancy bugs (like https://github.com/quotient-im/Quaternion/issues/702). I don't think Rust solves the general problem of preventing deadlocks within and between processes (which often cross organizational boundaries between projects and distinct codebases, with no clear contract on allowed behavior and which party in a deadlock is at fault), and non-atomicity between processes on a single machine (see my PipeWire criticism at https://news.ycombinator.com/item?id=31519951). File saving is also difficult (https://danluu.com/file-consistency/), though I find that fsync-then-rename works well enough if you don't need to preserve metadata or write through file (not folder) symlinks.

> OCaml’s configure script is also “normal”

If that’s this OCaml, it has a configure.ac file in the root directory, which looks suspicious for an Autotools-free package: https://github.com/ocaml/ocaml

You probably already know, but with OCaml 5 the only way to get flamegraphs working is to either:

* use framepointers [1]

* use LBR (but LBR has a limited depth, and may not work on on all CPUs, I'm assuming due to bugs in perf)

* implement some deep changes in how perf works to handle the 2 stacks in OCaml (I don't even know if this would be possible), or write/adapt some eBPF code to do it

OCaml 5 has a separate stack for OCaml code and C code, and although GDB can link them based on DWARF info, perf DWARF call-graphs cannot (https://github.com/ocaml/ocaml/issues/12563#issuecomment-193...)

If you need more evidence to keep it enabled in future releases, you can use OCaml 5 as an example (unfortunately there aren't many OCaml applications, so that may not carry too much weight on its own).

[1]: I haven't actually realised that Fedora39 has already enabled FP by default, nice! (I still do most of my day-to-day profiling on an ~CentOS 7 system with 'perf --call-graph dwarf', I was aware that there was a discussion to enable FP by default, but haven't noticed it has actually been done already)

11. OCaml - $91,026

> It partially helps since it forces you to have types where they matters most: exported functions

But the problém the OP has is not knowing the types when reading the source (in the .ml file).

> How would it feels like to use list if only https://github.com/ocaml/ocaml/blob/trunk/stdlib/list.ml was available,

If the signature where in the source file (which you can do in OCaml too), there would be no problem - which is what all the other (for some definition of "other") languages except C and C++ (even Fortran) do.

No, really, I can't see a single advantage of separate .mli files at all. The real problém is that the documentation is often worse too, as the .mli is autogenerated and documented afterwards - and now changes made later in the sources need to be documented in the mli too, so anything that doesn't change the type often gets lost. The same happens in C and C++ with header files.

If you have been in the Ruby community for the past couple of years, it's possible that you're not a super fan of types or that this concept never passed through your mind, and that's totally cool. I myself love the dynamic and meta-programming nature of Ruby, and honestly, by the time of this article's writing, we aren't on the level of OCaml for type checking and inference, but still, there are a couple of nice things that types with sorbet bring to the table:

Looks like there have been proposals to eliminate use of 3 operand lea in OCaml code (not accepted sadly):

https://github.com/ocaml/ocaml/pull/8531

An amazing example is Ocaml lang logo / mascot. It might be useful to talk with them to know what was the process behind this work. The About page camel head on Perl dot org header is also a pretty good example of simplification, but it's not a logo, just a friendly illustration, as the O'Reilly camel is. Another notable logo for this animal is the well known tobacco industry company, but don't get me started on that (“good” logo, though, if we look at the effectiveness of their marketing).

Haskell and Agda are probably the most obvious examples. Ocaml too, but it is much older, so its type system is not as categorical. There is also Idris, which is not as well-known but is very cool.

That does sound problematic, but without the code it is hard to tell what is the issue. Typically, compiling a 6kLoc file like https://github.com/ocaml/ocaml/blob/trunk/typing/typecore.ml takes 0.8 s on my machine.