Jane Street is known for being an OCaml shop, but for years now Python has been our second major programming language, acting as the primary tool for data analysis and (especially importantly these days) machine learning. Most of our trader…
I’ve been telling people for the last 25 years that Jane Street as an organization was just not interested in formal methods. It’s not exactly that I think we were wrong all those years. To be clear, we’re strong believers in the power of t…
We’ve always found strace useful but somewhat hard to work with. Its output is often inscrutable, it’s hard to follow subprocesses or threads, and if you want to filter syscalls you have to rerun the trace with a flag for each one. What you…
Attention is a computational primitive at the core of modern language models, allowing internal representations to reference and influence each other. It’s how these models handle sequential data in the first place.
Using ASCII waveforms to test hardware designs Finding memory leaks with Memtrace Attention is a computational primitive at the core of modern language models, allowing internal representations to reference and influence each other. It’s ho…
A lot of “capture-the-flag” style ML puzzles give you a black box neural net, and your job is to figure out what it does. When we were thinking of creating our own ML puzzle early last year, we wanted to do something a little different. We
At the end of last year, we decided to try something new: a challenge that would run alongside Advent of Code, where we asked the community to show us how they could design hardware to solve the same problems. We had no idea what level of p…
For a long time I was skeptical of LLMs—whenever I reached for them I was disappointed by the results. Last year I tried Copilot and Cursor to tweak a game I’d built, and neither generated working changes. At a previous job I tried Gemini t…
Using ASCII waveforms to test hardware designs Finding memory leaks with Memtrace For a long time I was skeptical of LLMs—whenever I reached for them I was disappointed by the results. Last year I tried Copilot and... I recently ported the
I recently ported the Hardcaml_step_testbench library, one of the libraries that we use at Jane Street for Hardcaml simulations, from using monads to using algebraic effects, a new OCaml 5 feature. This blog post walks through what algebrai…
Testing is an essential part of building reliable software. It’s a form of documentation, a reminder of mistakes of the past, and a boost of confidence when you want to refactor. But mostly, testing is a way of showing that your code is cor…
At Jane Street, we’ve been actively making improvements to OCaml for a long time. Over the last few years, we’ve started to build some fairly ambitious extensions to the language. Our aim is to make OCaml a great language for performance en…