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

We are excited to announce the launch of the Jane Street Graduate Research Fellowship ..read more

We are excited to announce research internships in our Tools and Compilers group ..read more

Software engineering intern candidates often ask how team placement works and how much input incoming interns have over their teams and projects. We know team placement is an important factor for many students when deciding which internship to accept. We’ve spent considerable time and thought on this process in recent years and hope to demystify the experience with this post. 1 This process is used in New York and London. Due to their smaller size Hong Kong’s process is slightly different  ..read more

Intel Processor Trace is a hardware technology that can record all program execution flow along with timing information accurate to around 30ns. As far as I can tell almost nobody uses it, seemingly because capturing the data is tricky and, without any visualization tools, you’re forced to read enormous text dumps ..read more

We spend a lot of time on education at Jane Street. Like, really a lot ..read more

We recently restructured our standard libraries at Jane Street in a way that eliminates the difference between Core_kernel and Core and we’re happy with the result. The new layout should reach the open source world before the end of the year ..read more