All blog posts

Java in the Technology Radar (JavaSpektrum)

I’ve written a new article for JavaSpektrum: “Java im Technology Radar – Totgesagte leben länger”. The piece looks back at Java’s journey through the eyes of the Thoughtworks Technology Radar...

Structured Concurrency in Java 24 (JavaSpektrum)

I’ve written an article for JavaSpektrum 2/2025 about Structured Concurrency in Java 24. The article covers JEP 499, Java’s fourth preview of Structured Concurrency, which aims to make concurrent programming...

Who Ensures Quality in the Scaled Agile Framework (SAFe)?

As an external consultant in an Enabling Team for Cloud Architecture, I supported several teams and noticed that software development quality was lacking. This surprised me because the client was...

Generating dialogues with OpenAI's API

During the winter holidays I had some fun letting AIs discuss with each other about various topics. I personally like to chat with ChatGPT and challenge it (him/her) with difficult...

Using OpenAI's API to generate prompts for images

The advances of artificial intelligence in the last months are simply breath taking. It is now very easy to use “intelligent” APIs in your web app. In this example application...

Test driven development of concurrent programs in Kotlin at KKon 2022

Concurrent and asynchronous applications can be written in Kotlin with coroutines in a precise and structured way. Unfortunately, concurrency often increases the complexity and it is difficult to create bug-free...

Coroutines in Kotlin at KKon 2021 Warmup

In my talk “Nebenläufigkeit mit Koroutinen strukturieren” at the KKon 2021 Warmup I explained how to structure and organize concurrent programs with coroutines in Kotlin.

The Ray Tracer Challenge in Kotlin

During the chrismas holiday I started a new ray tracer in Kotlin while following the book “The Ray Tracer Challenge.

Update of my website to Bootstrap 5

I updated my website so that it looks new and shiny and provides faster and easier access.

Refactoring with the Mikado Method

At a client of ThoughtWorks I gave a talk about refactoring in line with the book “Mikado Method”. The book describes a method to plan and perform non-trivial refactorings of...

A short introduction to Kotlin

At a client of ThoughtWorks I gave a talk about the advantages of Kotlin.

Plain react, hooks and/or Redux

At a client of ThoughtWorks I gave a short presentation about three different ways of state management in React.

Coroutines in Kotlin and Go in iX Developer - "Weniger warten, asynchron arbeiten"

In the article “Verteilte Systeme: weniger warten, asynchron arbeiten” (distributed systems: less waiting, asychronous working) in the german magazine iX Developer Moderne Softwareentwicklung - code(), build(), deploy() I explain the...

Migrating a ray tracer from Java and Groovy to Kotlin (part 3)

I continued to work on migrating my ray tracer to Kotlin. Now the scenes can be specified with a Kotlin DSL and all Groovy code is gone.

Coroutines in Kotlin and Go on heise Developer

In the article “Weniger warten, asynchron arbeiten” (less waiting, asychronous working) published by heise Developer I explain the theoretical background of coroutines and how to use them in Kotlin and...

Concurrency in Kotlin with coroutines

Coroutines are a “new” way to handle concurrency on the JVM. I gave an introduction to coroutines in Kotlin at Thoughtworks. This is basically the translation of the german slides....

Talk about coroutines in Kotlin at the parallel 2019 conference

Coroutines are a “new” way to handle concurrency on the JVM. At the para//el 2019 conference, I gave an introduction to coroutines in Kotlin.

Fusion of object oriented and functional programming

The fusion of Object Oriented Programming (OOP) and Functional Programming (FP) languages has become increasingly popular in recent years, with many programming languages now offering features and constructs from both...

Machine learning library 'cuDNN' explained in iX Developer

It’s very difficult to implement algorithms optimally for GPUs. Therefore NVIDIA provides the library cuDNN for deep learning with neural networks. This article published in the german magazine iX Developer...

Migrating a ray tracer from Java and Groovy to Kotlin (part 2)

I continued to work on migrating my ray tracer to Kotlin.

Migrating a ray tracer from Java and Groovy to Kotlin (part 1)

After reading the wonderful book Kotlin in Action I started to migrate my ray tracer from Java and Groovy to Kotlin.

EuroClojure 2017 in Berlin

In my first project for ThoughtWorks the backend is written in Clojure. Since the project was in Berlin, I visited the EuroClojure 2017 which takes place in Berlin this year,...

Talk about GPU computing with CUDA and OpenCL

In March 2017 I gave a talk about GPU computing with CUDA and OpenCL at the para//el 2017 conference in Heidelberg, Germany.

Working for ThoughtWorks

After long considerations i decided to quit being a freelancer and joined ThoughtWorks in Hamburg, Germany.

CUDA 8.0 on Mac OS/X

CUDA 8.0 on Mac OS X 10.12 gave me the following error:

Updated library of geometric algorithms

Today I released an updated version of the library of geometric algorithms.

Visualizing family names with Node, Angular, and D3 for Coding da Vinci Nord 2016

As part of the cultural hackathon Coding da Vinci Nord 2016, I built a web application for the analysis and visualization of the distribution of family names. I used (among...

Using a __device__ lambda in CUDA 8.0

In CUDA 8.0 C++ 11 lambdas can be used on the device. See the following code.

The 'Complex' Perspective - Introduction to the Digital Economy

Humanity has arrived in the information and knowledge society. No sooner have the first changes been digested than more news appears on the horizon: the Internet of Things, Big Data,...

Slides: 'Business Models - A Short Overview'

Slides for an introduction to business models and business model patterns.

Ray tracing with Groovy and Java

While I was reading the excellent book by Kevin Suffern "Ray tracing from the ground up", I implemented a ray tracer in Java and wrote a DSL in Groovy, to...

Covariance and Contravariance in Scala

The topic of covariance and contravariance is explained in many places (including Wikipedia). This post is my attempt to explain it in my own words, using Scala.

Covariance and Contravariance in Scala

I explain "covariance and contravariance" with some simple Scala examples.

k-d-trees with Apache Spark and Scala

This article shows how to use k-d-trees with Apache Spark.

Using Elasticsearch with Spring Boot - Analyzing the emails with Kibana

This is the last part in a series of four. It shows how to analyse the emails with Kibana.

Using Elasticsearch with Spring Boot - Technical background

This is the third part in a series of four. It explains the technical background.

Using Elasticsearch with Spring Boot - Installation and Usage

This is the second part in a series of four. It shows installation and usage.

Using Elasticsearch with Spring Boot

This article shows how to use Elastiksearch database with Spring Boot. It is the first in a series of four.

Heat diffusion on multiple GPUs

The implementation of the heat diffusion equation on multiple GPUs is explained in the talk (in german).

Measuring traffic on the PCI Express Bus (PCIe)

During my talk at the parallel 2015 conference i was asked how one can measure traffic on the PCI express bus. For multi GPU computing it is very important to...

Talk at the parallel 2015 about Multi-GPU programming with Cuda, OpenCL and C++ AMP

At the parallel 2015 conference I gave an introduction into Multi-GPU programming with Cuda, OpenCL and C++ AMP.

Trying out next-gen JavaScript now with ECMAScript 6

With Babel you can test many features of the upcoming next version of JavaScript called ECMAScript 6 now.

Examples for parallelism: ray tracer on the GPU

I tested the parallel ray tracer on all NVIDIA cards i bought. This page contains the results.

Examples for parallelism: ray tracer

I wanted to learn some frameworks for parallel computing and i decided to implement a simple ray tracer as a "visual benchmark".

Talk at parallel 2014 about GPU-Computing

At the parallel 2014 I gave an introduction into the optimization of GPU kernels.

Two articles in iX Developer: GPU Computing mit CUDA

"Massiv parallel - Grundlagen der GPU Programmierung"

"GPU-Programmierung in der Praxis mit CUDA"

Talk at parallel 2012 about GPU-Computing

At the parallel 2012 I presented my experiences and learnings I gathered in GPU computing projects.

Slides: 'Introduction to Parallel Computing'

These slides are for a course about parallel computing.

Technical proofer of 'OpenCL in Action'

The OpenCL standard is not always easy and the technical proof was a challenge, because the code had to run on different os'es and platforms.

Using Scala and TestNG with Gradle

During the christmas holidays i tried out Scala and TestNG with Gradle.

Sony Alienates Early PlayStation 3 Fans

On April 1st, Sony released an update for the PlayStation 3 that discontinued support for Linux. This move angered many, sparking intense reactions and discussions.

Column-oriented databases

From 2002 to 2006, I worked at a Canadian manufacturer of a column-oriented database.

CUDA Real-Time Ray Tracer

During the christmas holidays i rewrote my ray tracer for the NVIDIA CUDA architecture.

Training: Test-Driven Development with JUnit 4

This training teaches test-driven development with a focus on JUnit 4. Other frameworks such as JUnit 3 and TestNG are briefly introduced as well (as of 2009).

Training: Subversion

This training on Subversion covers practical version control workflows.

Training: Ant in Depth

Apache Ant offers a lot of capabilities that many teams never end up using. This training dives into Ant’s more advanced features (as of 2009).

Compiling OpenCL programs on Mac OS X Snow Leopard

I installed Snow Leopard on my laptop yesterday. I was very curious about OpenCL and installed the drivers and the GPU Computing SDK from NVIDIA.

Groovy, EMF and UML2

I wrote the Groovy EMF builder and the Groovy UML2 builder. These tools use the builder concept of the programming language Groovy to ease the processing of Eclipse Modelling Framework...

Hyper-Threading with the Intel Core i7

I have got a new computer. As alway i build it myself. How much faster is it?

Parallelization with Haskell - Easy as can be

The functional programming language Haskell provides a very easy way of parallelization.

Real-Time RayTracer running on Intel Core i7

I tested my ray tracer on Intel Core i7 920 @2.67 MHz.

Real-Time RayTracer running on Core 2 Duo

I tested my ray tracer on my Mac Book Pro.

Parallelization with the Cell Broadband Engine

I wanted to learn about the cell broadband engine in the Playstation 3 and wrote a parallel ray tracer for it.

Little big planet and computer graphics

I am fascinated by the possibilities of modern computer graphics. It all began while playing the game Little Big Planet. It does not look like a computer game. It looks...

New version of the library of geometric algorithms in Haskell

Almost 10 years after the initial release, i released an updated version of the library of geometric algorithms in Haskell. It now builds with Cabal and requires the Glasgow Haskell...

Memoization in Groovy with a Decorator

Memoization is a well known optimization technique to avoid repeated calculations. With dynamic programming languages like Groovy it is possible to extend the behaviour of an already exisiting class at...

Dynamic Languages Shootout / OOP 2008

The german magazine JavaSpektrum organized the "Dynamic Languages Shootout" contest for the OOP 2008 conference. The challenge was to create a computer game similiar to Scrabble in a dynamically typed...

Accessing EMF models with JRuby

JRuby provides access to Java packages, so it is possible to use packages created with the Eclipse Modeling Framework (EMF).

6th place at the Dynamic Languages Shootout at OOP 2008

The challenge was to implement Scrabble® in a dynamically typed programming language. I used Groovy and Grails.

Writing Eclipse plugins with Groovy

Writing plugins for Eclipse with other languages than Java is not officially supported, but there is a way to write an Eclipse plugin with Groovy only.

Eclipse BugDays 2007

I participated at Eclipse BugDays in July, August, September, October, and November 2007 and helped debugging the Eclipse projects JDT, PDE/UI, and ECF.

Using UML2 with Groovy

The UML2 project provides an EMF based implementation of the UML 2.x metamodel in Java. With the EMFBuilder it is possible to create and process UML2 models.

Rapid Application Development with Groovy

While i was cleaning up my hard disk on my Linux in 2007, i needed a program that displays the disk usage graphically. I didn't find a suitable one on...

Using EMF with Groovy

This article shows how Groovy can be used with the Eclipse Modeling Framework (EMF).

Editor for the Common Warehouse Metamodel (CWM)

The Common Warehouse Metamodel (CWM) is a standard by the Object Management Group (OMG). The intention of CWM is to define a standard for metadata in Data Warehouses and Business Intelligence applications.

Higher order Markov chains in Ruby - Ruby Quiz #74

Here’s my second solution for the quiz No 74. It generates text with a first or higher order Markov chains. See also the first order version.

Markov chains in Ruby - Ruby Quiz #74

Here’s my solution for the quiz No 74. It generates text with a first order Markov chain.

Eclipse-Editor for data warehousing metadata with EMF

When i first heard of the Eclipse Modeling Framework (EMF) i got really excited, i tried it out and i wanted to use it.

Eclipse SQL Editor Plugin

I wanted to find out how hard it is to build a language editor in Eclipse. Back then I didn’t know of any open-source SQL editor (and there wasn’t one...

Graphical Editors with Eclipse

Over Christmas 2004, I built an EMF plugin for family trees. Around Easter 2005, I finally found the time to develop a GEF-based editor for it.

Fraud Detection with Artificial Intelligence

From 1999 to 2004, I collected information on the topic of ‘Fraud detection’ on my website. When I started this in 1999 as a research assistant at the University of...

Geometric algorithms in Haskell

In my diploma thesis I investigate functional programming and geometric algorithms

Dynamic Scheduling in Real-Time Systems

In this seminar paper (1996), written during my graduate studies in computer science, I cover scheduling algorithms for distributed real-time systems.

Optimal Fast List-Ranking and Prefix Algorithms

A seminar paper on optimal parallel algorithms for prefix sums and list ranking.

Graphics programming in c't

Programming TrueColor graphics with the Diamond Speedstar 24x