Jonathan Woollett-Light

Programming experience

I am an expert in Rust, I am experienced in C++, C and Python, and I am familiar with Zig, Ada, aarch64 asm, RISC-V asm, JavaScript and CSS3+HTML5. I am a frequent Open-Source contributor having contributed to ziglang, rustlang and popular Rust crates. I have a small educational YouTube channel where I very infrequently post videos about technical topics I find interesting (A little more than an introduction to - YouTube).

CI Metrics

November 2023 - Current, Rust JavaScript, & HTML+CSS

A product to track performance metrics (also known as continuous benchmarking) and integrate with GitHub. An Axum backend deployed to AWS EC2 with a MongoDB database, implemented with ~3.5k LoC. Currently development is focussed on experimentation with optimization algorithms for anomaly detection to produce a solution that accomplishes what AWS Lookout for Metrics does, but at a much lower cost and complexity. Aimed at possible wide adoption by developers. This project was motivated by my experience working on Firecracker at AWS where regressions that could have cost millions in production were almost missed, and certainly some were.

My programming language

August 2023 - Current, Rust & Assembly

A language aiming to be as simple as C, as safe as Ada Spark and as convenient as Python. Formal verification is integrated into the compiler supporting full type inference removing the need for any generics/templates.

My web server

February 2023 - Current, Rust

A server framework implementing live migration. A new server process can succeed a local old process in milliseconds with shared memory (or remotely in seconds over TCP) without dropping client streams. This can be used as a database server with in-memory data storage akin to Redis where queries are compiled as new functions.

RUST-AD

December 2021 - January 2022, Rust

Auto-differentiation library with code transformation for both forward and reverse auto-diff.

Mathematics Site

April 2021 - June 2022, Rust, Python, JavaScript & HTML+CSS

A PWA to automate mathematics digitisation, enabling automated marking. An Actix backend using a PyTorch semantic segmentation model, deployed with AWS, with a MongoDB database. This is my largest personal project at ~32k lines and ~170k line changes. This project was a victim of my student ambition while in university, I came to the conclusion that while I had learned a great amount and built a cool project it was too big to make it into a valuable product on my own. This led me to focus on smaller but more complex projects moving forward.

GLSL BLAS

September 2020 - April 2021, GLSL & C++

GLSL code for non-complex BLAS operations with Vulkan. My final year masters project. I took advantage of modern C++ features to offer extensive compile-time evaluation to ensure shaders were as correct as possible.

BLAS website

September 2021 - October 2021, Python, JavaScript & HTML+CSS

A website documenting BLAS operations. While working on GLSL BLAS I found the older website used to document BLAS to be a little uncomfortable, so I made this.

Cogent

September 2019 - March 2021, Rust

A simple library for training simple neural networks, a small Keras. A component of my final year bachelors project.

Genetic Draughts AI

2016, C++

A simple tree search program to play draughts using a genetic algorithm to judge board positions. My first ever venture into optimisation, I still remember the moment it beat me.

Work experience

Amazon Web Services

Cambrigde - Software development engineer

I worked on Firecracker, a memory efficient, fast booting VMM that allows AWS lambda to be profitable.

Firecracker supports snapshotting a VM; a VM can be saved and restored much faster than booting a new one and much faster than any other VMM. I spent time working on the safety and configurability of this feature, this involved evaluating whether a snapshot could be safely restored on a given CPU considering its specified features and security mitigations, and those of the target. This involved analysis of the performance and security effects of CPU features on both x86-64 and aarch64, and ensuring we had an implementation that aligned with the specifications.

Firecracker supports a feature called CPU templates that allows a user configurability of most of how the CPU is presented to the guest OS. This work required understanding the Intel x86-64, AMD x86-64 and Arm aarch64 specifications. Development involved thorough discussion with customers and within our team both focused on usability, security and robustness. I rewrote how Firecracker handles static CPU templates to support runtime CPU templates and wrote the foundational implementation for runtime CPU templates. I also implemented thorough compatibility checks for x86-64.

I was the owner of an initiative to performance test Firecracker in production-like scenarios, through this we discovered and fixed significant performance regressions that may have costed AWS Lambda millions of dollars if they went live. This work involved coordinating across teams and diving deep into the deployment and management of resources to setup the required environment and execute the useful tests.

In this role I and another team member adopted responsibility for maintenance of the rust-vmm open source organization that maintained components used by Firecracker and other VMMs such as cloud-hypervisor.

Renishaw

Wotton-under-Edge - Software placement

I worked on building C++ components forming an internal standard library. This involved extensive testing and performance consideration.

Renishaw

Wotton-under-Edge - Work experience

My work experience focused on development with FPGAs and VHDL.