Visualization Testing Laboratory for Exascale Computing HIGH PERFORMANCE COMPUTING CENTER STUTTGART Sever Topan Computer Engineering Student University of Toronto
Intro/Overview Over the past summer I took part of a research exchange to the University of Stuttgart. The placement was organized through the SUPER research program at the University of Stuttgart to which I applied from the Center for International Experience at the University of Toronto. The placement lasted 3 months, between June 1 st and August 27 th, 2016. During this period, I worked at the High Performance Computing Center of Stuttgart (HLRS) as part of the visualization team. My direct supervisor was Martin Aumüller, and the Head of the Visualization Department under which I was recruited was Dr.-Ing. Uwe Wössner. Weekends and time off was spent exploring Germany and nearby countries such as Switzerland, France and the Czech Republic. The exchange in Europe developed my appreciation for art and culture as well as my prowess living on my own in a foreign environment. The report is split into two major parts, equating to the two basic ways my time in Europe was spent; The first relates to my research project and the work environment surrounding it, and the second describes my exploration of Europe and my impressions of its culture. PAGE 1
The HLRS Institute The research project which I worked on over the summer took place at the High Performance Computing Center of Stuttgart as part of the Visualization Team. The highlevel description of their task is to take raw simulation results from the computing clusters housed within the Computing Center, and to visualize them to the user. PROJECT DESCRIPTION My research project involved developing software for an application known as the Visualization Testing Laboratory for Exascale Computing (or Vistle ). It takes in simulation results and visualizes them using media such as virtual and augmented reality. This application is meant to be the successor of a visualization program that has been in use for 20 years at the HLRS. Its main advantage is that it runs on computer clusters, doing work in parallel. An advantage of this is scalability: the performance of the application can be scaled upwards by adding more computer nodes instead of using a more powerful computer. This is important because simulation results can be hundreds of Gigabytes in size, and analyzing them without a distributed system would be extremely slow. I learned many programming tools over the course of the summer including Git, Vim and Doxygen, as well as C++ API s such as Boost Serialization, Boost MPI, Boost MPL, and the Parallel and Serial HDF5 Libraries. My direct supervisor, Martin Aumüller took a lot of time guiding me through the usage of these tools, along with the structure of Vistle and software design principles to be used when dealing with cluster computing. I was tasked with implementing several aspects of the program over the summer, listed below. All work can be found online on GitHub, where Vistle s open source code is housed (https://github.com/vistle/vistle) - My main focus was developing a set of modules that can save Vistle data objects in a partially processed state, effectively saving compute time. This was achieved by using the Parallel HDF5 API to store data to an HDF5 file system collectively across the computing nodes. Two operating modes were implemented within the module, a organized mode that trades performance for a clearer HDF5 file structure, and a performant mode. - I helped lay the groundwork for Structured Grid support within Vistle. Structured grids are a major subset of data structures used in modern high performance computing simulations. Having support for Structured Grids allows for significant performance optimizations to be implemented. - I implemented a debugging module that prints data object metadata and added functionality to the GenDat module such as generation of ghost cell data. The GenDat module is responsible for generating regular test data for debugging purposes. PAGE 2
Above: A screenshot of Vistle. On the left the rendered simulation result of a pump turbine can be seen, while on the right, the modular workflow of the application is visible. Image taken from https://www.hlrs.de/en/vistle/ WORK ENVIRONMENT The work environment at the HLRS was unique and amazing for me. I don t think I could have found a research placement that fit the niche of what I found interesting better than what was offered here. To begin, the HLRS houses the European Union s most powerful supercomputer, as well as several other High Performance Computing Clusters. The facility has a hypermodern feel to it, and an abundance of novel technology present within it. The institute houses a CAVE, and small room where 5 out of the 6 walls are projected onto in 3D, giving a total feel of immersion. A Porsche driving simulator, a large tiled display, 3D scanners, and several augmented reality setups are all tinkered on by the Visualization Department. Left: Myself in front of the Hazel Hen Cray Supercomputer at the HLRS, the 9 th most powerful supercomputer in the world Right: An airflow simulation overlaid onto a live video feed of a Porsche 911 Turbo using augmented reality PAGE 3
VISUALIZATION TEAM The visualization team which I worked as a part of was extremely welcoming and was a pleasure to work with. As mentioned above, members took time to teach us tools and principles required for the tasks we were assigned. Biking and Rock Climbing were very popular sports among the team members. For lunch, we would ride bicycles down to the nearby Max Plank institute to eat. One of the team members would sometimes bring his tandem bicycle as well, which can be tricky to operate and requires some solid synchronization between its riders. Several events were also organized by the visualization team, such as a rock climbing outing and a barbeque to which we brought all our equipment by bicycle. Through this we were able to experience parts of German culture that we would not have otherwise, such as trying out Stockbrot, bread dough roasted over a campfire. It is served in both sweet and savory varieties. Above: Taking the tandem bicycle to lunch on a hot day with a fellow SUPER student Left: Learning Rock climbing tips from the head of the Visualization Team, Uwe Wössner PAGE 4
Outside the Workplace Being close to Germany s southern border, Stuttgart is an excellent hub from which to travel. Over the weekends the SUPER students would often group up and explore different destinations together. I had the opportunity to tour many places during the 3 months spent in Germany: Zurich, Strasbourg, Prague, Cluj-Napoca, Munich, Ulm, Heidelberg and Konstanz were the more major destinations. If I had to categorize the elements of the European environment that stood out, it would be the following 3 things: Art and Historic Precedence, Food, and Social Culture. ART AND HISTORIC PRECENDECE Growing up in Canada does not really yield a sense of large historic precedence. Canada is an extremely young Country; If you were to walk through the downtown of a North American city, you would find skyscrapers and blocks built mainly with a post-1950 architectural style. Even if you were to delve into the Old Town of a Canadian City, buildings would not age past the late 1800 s. This stands in significant contrast to European cities which have been bustling for hundreds of years. This historic age shows itself through amazing monuments, churches, parliamentary buildings and other architecture and art pieces throughout each city. FOOD One thing that I will definitely miss is the food in Europe. Grocery store items are relatively cheap and of high quality. The mere raw ingredients used to make food yield a much crisper flavor than the ones I was used to. This is especially present in dairy products; I will never look at Brie cheese in the same way after this trip. With this potent base of ingredients, restaurants weave together amazing recipes. I had the pleasure of sampling signature food from most of the countries visited. Some that stood out for me are Weisswurst and Maultasche from Germany, Raclette from Switzerland, Czech Breakfast Dumplings and French Escargot. The cultural density surrounding European cuisine astounded me, not to mention the quality and taste. SOCIAL CULTURE The final aspect that left an impression on me is social culture in Germany. European cities are much more geographically dense than North American cities. This plays into a dynamic that seems much more social than that of North America. North America is extremely car-centric; Often sidewalks are completely deserted down city streets while people sit isolated in their cars waiting for the next light to turn green. Conversely, I could reach virtually anywhere in Stuttgart in reasonable time with nothing more than a train pass. Being able to travel on foot and interact closely with others on a constant basis plays into this feeling of being in a more social society. PAGE 5
Top: Artchitecture: a beautiful view of Schlosss Heidelberg from a city square Bottom Left: A delicious meal overlooking water channels in Strasbourg Bottom Right: Sharing the view over Lake Zurich with the Swans PAGE 6
Conclusion Overall the experience that the SUPER program provided me was unique and amazing. I don't think I could have found a better combination between how interesting the work placement was and the ability to explore Europe and its culture. I would definitely recommend the SUPER program to any prospective students. PAGE 7