We live in Heidelberg, Germany. About once a year we travel to my wife’s hometown of Taiyuan, the capital of the Shanxi province in China, to visit my parents-in-law. Our most recent visit was in spring of this year, for two months. In this post I’ll talk about my experiences of regularly staying in...

At Materialize we’ve had success in finding bugs in existing code and open pull requests using LLM-based coding agents since February 2026, coinciding with the release of Anthropic’s Opus 4.6 (now mostly running on 4.7). In this post we’ll look into some of the considerations that went into the syst...

When customers hit issues in production, it can be an effort to locally reproduce them, especially when external sources are involved. Reproducing issues is useful not just to figure out the root cause, but also to verify the fix and add a regression test. The newly introduced workload capture & rep...

In the previous post I talked about how we test Materialize. This time I’ll describe how I significantly sped up our Continuous Integration (CI) Test pipeline in July, especially for pull requests that require a build and full test run. The goal is to make developers more productive by reducing the ...

In our last blog about our Quality Assurance (QA) team, we gave an overview of the QA process, including our software and testing methods. One of our key tools during testing is the Materialize Emulator, a Docker image that allows you to maintain a locally hosted version of Materialize. Read the res...

I analyzed a flaky test failure in our Materialize CI today: $ docker compose up -d --scale default=0 default no such service: default mzcompose: error: running docker compose failed (exit status 1) I had seen this error already once or twice in the last year, but it was incredibly rare in our Conti...

I joined Materialize’s Quality Assurance (QA) development team over a year ago. Since our team is small, we have to be conscious about focusing our time on the most impactful testing and test tooling. Our goal is to find issues in Materialize as early and as efficiently as possible, ideally before a...

Or how to make naïve hosters shut down your victim’s server. Do you want to bring down your victim’s game servers? Do they host their game servers on cheap VPSes at hosters who are not that experienced with networking? Is running an actual DoS against the server too expensive and illegal for you? Ju...

Note: This is translated from the German original, which was used as a homework for the Programming Paradigms course at Karlsruhe Institute of Technology a long long time ago when I was co-holding the practical courses. Snake is a computer game in which a snake has to be moved through a playing fiel...

God famously does not play dice with the universe, but he seems to enjoy writing Haskell: Consider the wave-particle duality in quantum mechanics. Every particle behaves as a wave, as long as you haven’t interacted with it. Thanks to Haskell’s lazy evaluation values are also only evaluated once they...

YugabyteDB is a cloud-native database for business-critical enterprise applications. It is designed to provide continuous availability as well as horizontal scalability, while retaining a strong set of RDBMS features. This objective creates a strong quality incentive for us in the Yugabyte Quality A...

As a relief for rising energy costs and inflation Germany is offering nearly-free public transportation for the months of June, July and August. For just €9 per month you can take any kind of regional public transportation in all of Germany. That’s basically everything except the IC/ICE for long dis...

In my previous post 8 months ago I described how our open source online game DDraceNetwork has been suffering under DoS attacks for about 8 years, basically since its inception. Recently the attacks have gotten much worse, forcing us to work on further approaches. Since many players made suggestions...

About 3 years ago I wrote about my Linux Desktop Setup and having used pretty much the same software setup for 10-15 years. My setup used to be heavily keyboard based. Now for work I am for the first time using a macOS-based Macbook Pro with an M1 Pro CPU. I spent the last 3 weeks using it as a dail...

DDraceNetwork is an open source online game I’ve been running since 2013 with a community of volunteers. The game is available for free, I’m hosting servers for it in many countries around the world so that we have trusted official ranks. The servers are paid for by donations, which I stop collectin...

Today I lost access to my home server. As I described in a previous post I depend heavily on the server to fetch my emails, as a file server, to synchronize files, for newsbeuter and irssi sessions and many other things. As no one was going to be in proximity of the server for the next few hours, my...

Nearly two years ago I posted this endless GIF that always shows the current time in UTC: Now looking at my GoAccess dashboard I can see that it is picking up in popularity rather suddenly: But strangely I can’t find anything about time.gif being linked on the web. So this might just be an attempted...

Russian Translation by Akhmad Karimov My software setup has been surprisingly constant over the last decade, after a few years of experimentation since I initially switched to Linux in 2006. It might be interesting to look back in another 10 years and see what changed. A quick overview of what’s run...

Some people really liked the dark DDNet theme for Halloween by Soreu, so we decided to keep it possible to use the default bright or the dark theme. Thanks to xse we got a JavaScript based theme switcher. After some improvements I finally I switched it away from JavaScript entirely and finally am al...

Exactly on this day, one year ago, I came back from a one month long trip to Taiwan, went straight to work from the airport and immediately moved into a new apartment after work. Since then I have cycled to work nearly every day. Fullscreen (map made with umap, routes made with GraphHopper) Alternat...

I have recently received a job offer to work on a blockchain implementation. While the offer was very generous, I had to turn it down. In this post I want to collect the thoughts that went into my decision process leading to this conclusion. Introduction I have not touched blockchain technology much...

I started working as a C++ developer in the HANA Core Platform team at SAP in Walldorf, Germany more than a year ago. In this time I have gotten some insights into the development environment and processes. I will use this post to illustrate them by the example of adding a small new feature and expl...

What is the output of this small snippet that is based on real C++ code? #include <iostream> struct Foo { Foo() { std::cout << "standard" << std::endl; } Foo(const Foo&) { std::cout << "copy" << std::endl; } Foo(int) { std::cout << "int" << std::endl; } Foo(int, int) { std::cout << "int, int" << std...

This is an endless GIF that always shows the current time in UTC: Source Code (From reports it doesn’t seem to work on Safari, other browsers should be fine.) time.gif is written in Haskell and works by dynamically generating each frame of the GIF and slowly feeding them over the HTTP connection. Th...

Creating code coverage reports with Nim is surprisingly easy. You can simply use the good old gcov and lcov tools. Nim can be told to insert its own line information with the --debugger:native command line parameter. Here’s the small example program we’re looking at: var x = 0 if x > 1: echo "foo" e...

In this post I want to highlight a few fun aspects of the Haskell programming language. The purpose is to give you a taste of Haskell so that you will want to learn more of it. Don’t consider this as a tutorial or guide but rather as a starting point, as it is based on a short talk I held at work, w...

In my latest post I showed some examples of how I ran mostly the same PC hardware over a period of 8 years. Today I finally finished setting up my new PC hardware in my new home, so I can report about what I did differently, my thought process, and some problems I encountered and hacks I did to solv...

After reading the feedback of my recent article about running DDNet, I noticed that people found it interesting how I’m trying to minimize money and resources. I also noticed that I had been doing something similar with my personal computing hardware setup for an even longer time. I’ve mostly been u...

Japanese Translation In this article we’re going to write a simple 2D platform game. You can also consider this as a tutorial for game development with SDL2 in Nim. We will read in user input, display graphics and a tile map, and simulate simple 2D physics with collision detection and handling. Afte...

It’s been roughly 3 years since DDraceNetwork (DDNet) started in the summer of 2013. Last year I wrote a non-technical History of DDNet. Today in this post we will dive into the technical side of what makes DDNet run. For the uninitiated, DDNet is an open-source modification of Teeworlds, a retro mu...