We’re once again at the end of our internship season, and it’s my task to provide a few highlights of what the dev interns accomplished while they were here ..read more

OCaml with Jane Street extensions is available from our public opam repo. Only a slice of the features described in this series are currently implemented ..read more

Jane Street is excited to announce our sponsorship of SoME3, Grant Sanderson and James Schloss’s third Summer of Math Exposition. SoME is a contest that Grant and James created to encourage the development of fun and interesting mathematics education videos ..read more

In part one, we discussed how OCaml’s locality mode enables safe stack allocation. In this post, we will explore additional modes for representing ownership ..read more

Coming from OCaml, the Rust programming language has many appealing features. Rust’s system for tracking lifetime and ownership allows users to safely express patterns that are awkward in OCaml, such as ..read more

Our traders and researchers love Python for its agility and for its huge open-source ecosystem, especially when it comes to machine learning. But the heavy use of notebooks can make it difficult to support. Notebooks have a very different lifecycle than regular code, and aren’t always rigorously version controlled. And while most of our code (much of it written in OCaml) lives in a monorepo, putting all notebooks there is difficult; many notebooks end up being stored all over the place ..read more

At Jane Street we use a pattern/library called “expect tests” that makes test-writing feel like a REPL session, or like exploratory programming in a Jupyter notebook—with feedback cycles so fast and joyful that it feels almost tactile. Having used them for some time now this is the only way I’d ever want to write tests ..read more

In 2022 a consortium of companies ran an international competition, called the ZPrize, to advance the state of the art in “zero-knowledge” cryptography. We decided to have a go in our free time at submitting solutions to both the Multi-Scalar Multiplication (MSM) and Number Theoretic Transform (NTT) tracks, using the same open source Hardcaml libraries that Jane Street uses for our own FPGA development. We believe by using Hardcaml we were able to more efficiently and robustly come up with designs in the short competition period. These designs also interact with the standard vendor RTL flow an ..read more

The Dojima rice market, established around 1716, is widely considered to be the world’s first organized futures exchange. Instead of directly exchanging money for rice on the spot, merchants would agree on a price and future date at which rice and money would be exchanged. This allowed farmers and consumers to hedge their risk. As a result, information about the abundance or lack of rice would travel across the country as fast as rice merchants carried it ..read more

One of the problems we wrestle with at Jane Street is how to understand and manage the costs associated with the positions we hold: things like margin, financing costs, market risk, regulatory capital requirements, and so on. To that end, we’ve built systems that estimate these costs and propose ways to reduce them. Essentially, this is a numerical optimization problem ..read more