Often in error, never in doubt.
2026-02-17 A vibe-coded alternative to YieldGimp If you’re a UK tax resident, short-term low-coupon gilts are the most tax efficient way to get savings-account-like returns, since most of their yield is tax free. This makes them very popular amongst retail investors, which now hold a large portion of the tradable low-coupon gilts. YieldGimp.com used to be a great free resource to evaluate the…
2025-10-17 Hidden benefits of undefined behavior I was reviewing some code at work, and something jumped at me when reading some arithmetic: static inline int64_t int32ToDecimal9 ( int32_t i ) { return i * 1000000000 ; } If you’ve had the good fortune of dealing with C or C++ for extended periods you would have recognized the problem. i * 1000000000 will be performed with 32-bit precision, which…
2025-09-25 Open sourcing TernFS, a distributed filesystem A few days ago we open sourced TernFS, a distributed filesystem which has been used in production at XTX for a couple of years now. The project took up a big chunk of my waking hours for a year and a half, and I’m extremely happy that we are now sharing it with the world. You can find a blog post describing it on XTX’s tech blog , and the…
The standard Go toolchain comes with an assembler out of the box. Said assembler is highly idiosyncratic, using syntax inherited from Plan 9 and choosing its own names for platform-specific instructions and registers. But it's great to have it readily available. More mundanely, Go comes with a garbage collector. This post explains how to make these two components play nice, if we want to…
2025-06-09 inline-verilog : Execute Verilog circuits from Haskell Like for most of the past 13 years, early June meant attending ZuriHac . The event was as pleasant and well organized as ever. While talking to Ed Kmett he half-jokingly mentioned that it would be useful to have a Verilog analogue of inline-c , especially to test Verilog circuits against Haskell functions. A few hours later I had…
When doing systems programming we often need to wait for something to happen. Common examples might be waiting for some data to come through a socket or waiting on a lock. We also often want to wait on any of several conditions to become true. A web server might be handling many sockets at once, waiting for any number of them to become readable or writeable. This short blog post is concerned with…
In a companion blog post I talked about how to effectively combine Reed-Solomon coding and CRCs. To do so I presented a few functions to manipulate CRCs. In this post I'll explain why and how they can be implemented.
In my latest filesystem-themed post I discussed a technique to perform distributed resource management more safely. This time I'll explain how one might effectively combine _Reed-Solomon coding_ and _cyclic redundancy checks_. The first gives us redundancy (we can lose disks and still recover our data), the second protects us against data corruption.
I've been developing and quickly deploying a distributed system, which is a class of software where bugs are expensive. A few hundred petabytes later, we haven't lost a single byte of data, also thanks to a simple trick which catches a large class of bugs when delegating responsibilities to possibly buggy software. It's a neat use of cryptography beyond security, so here's a small description.
Stopping a Linux thread is a surprisingly annoying affair. In this post I present common pitfalls and some solutions -- although no truly satisfactory method exists.