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The Saga of Multicore OCaml

Jane Street is an electronic trading firm that uses low latency trading systems built in OCaml to provide liquidity to financial markets worldwide. In December 2022, after nearly a decade of development, OCaml 5.0 was released with OCaml’s first multi-core capable runtime. This was an exciting milestone, finally making it possible to write shared-memory parallel programs in OCaml. The new runtime was designed to be easy to adopt: it didn’t disturb OCaml’s FFI, and performance was meant to be only a few percentage points slower in single-core mode. Despite those promising beginnings, switching to runtime-5 within Jane Street was harder than we expected. Indeed, we've only just switched to it this year, after 2.5 years of research and engineering effort. This talk will give an overview of the problems we ran into, and what we learned from the process, including some new ideas that solved some very old problems in the design of OCaml's GC. Read the full transcript here: https://www.janestreet.com/tech-talks/the-saga-of-multicore-ocaml/

24 Jul 2025

Jane Street - Tech Talks

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Tarides Website

Bella was in touch as the tarides.com website is no longer building. The initial error is that cmarkit was missing, which I assumed was due to an outdated PR which needed to be rebased.

24 Jul 2025

Marc Elvers

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opam 2.4 release

Feedback on this post is welcomed on Discuss! We are extremely happy to announce the release of opam 2.4.0 and encourage all users to upgrade. Please read on for installation and upgrade instructions. Major changes On opam init the compiler chosen for the default switch will no longer be ocaml-syste...

23 Jul 2025

OCamlPro

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Slipshow x x-ocaml

23 Jul 2025

Patrick Ferris' OCaml Blog

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Package Tool

Would you like to build every package in opam in a single Dockerfile using BuildKit?

22 Jul 2025

Marc Elvers

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Depth-first topological ordering

Over the last few months, I have written several posts on the package installation graphs specifically, Topological Sort of Packages, Installation order for opam packages and Transitive Reduction of Package Graph. In this post, I’d like to cover a alternative ordering solution.

21 Jul 2025

Marc Elvers

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Learning OCaml: Having Fun with the Fun Module

When I started to play with OCaml I was kind of surprised that there was no id (identity) function that was available out-of-box (in Stdlib module, that’s auto-opened). A quick search lead me to the Fun module, which is part of the standard library and is nested under Stdlib. It was introduced in OCaml 4.08, alongside other modules such as Int, Result and Option.1 It was part of some broader efforts to slim down Stdlib and move in the direction of a more modular standard library. ↩

19 Jul 2025

Bozhidar Batsov

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