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Comment by loxs | Hacker News Reader

I migrated from OCaml to Rust around 2020, haven't looked back. Although Rust is quite a lot less elegant and has some unpleasant deficiencies (lambdas, closures, currying)... and I end up having to close one one eye sometimes and clone some large data-structure to make my life easier... But regardless, its huge ecosystem and great tooling allows me to build things comparatively so easily, that OCaml has no chance. As a bonus, the end result is seriously faster - I know because I rewrote one of my projects and for some time I had feature parity between the OCaml and Rust versions.

Nevertheless, I have fond memories of OCaml and a great amount of respect for the language design. Haven't checked on it since, probably should. I hope part of the problems have been solved.

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Your comment makes me think the kind of people who favor OCaml over Rust wouldn't necessarily value a huge ecosystem or the most advanced tooling. They're the kind who value the elegance aspect above almost all else, and prefer to build things from the ground up, using no more than a handful of libraries and a very basic build procedure.

Yeah, I was that kind of person, then I wrote a real tool that does real work in OCaml... and then I discovered than I am no longer such a person and went to Rust.

> the end result is seriously faster

Do you have a ballpark value of how much faster Rust is? Also I wonder if OxCaml will be roughly as fast with less effort.

Just the straight/naive rewrite was ~3 times faster for my benchmark (which was running the program on the real dataset) and then I went down the rabbit hole and optimized it further and ended up ~5 times faster. Then slapped Rayon on top and got another ~2-3x depending on the number of cores and disk speed (the problem wasn't embarrassingly parallel, but still got a nice speedup).

Of course, all of this was mostly unneeded, but I just wanted to find out what am I getting myself into, and I was very happy with the result. My move to Rust was mostly not because of speed, but I still needed a fast language (where OCaml qualifies). This was also before the days of multicore OCaml, so nowadays it would matter even less.

> straight/naive rewrite was ~3 times faster

How much of that do you think comes from reduced allocations/indirections? Now I really want to try out OxCaml and see if I can approximate this speedup by picking up low hanging fruits.

I would imagine most of it, because the program in question mostly does parsing and ETL.

Were you using the ocamlopt compiler? By default, ocaml runs in a VM, but few people figure that out because it is not screaming its name all the time like a pokemon (looking at you JVM/CLR). But ocaml can be compiled to machine code with significant performance improvements.

> By default, ocaml runs in a VM,

The Dune build system does default to ocamlopt nowadays, although maybe not back around 2020.

Yeah, I just checked in my repository, it was ocamlopt

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