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SCCS Colloquium

The SCCS Colloquium is a forum giving students, guests, and members of the chair the opportunity to present their research insights, results, and challenges. Do you need ideas for your thesis topic? Do you want to meet your potential supervisor? Do you want to discuss your research with a diverse group of researchers, rehearse your conference talk, or simply cheer for your colleagues? Then this is the right place for you (and you are also welcome to bring your friends along).

Upcoming talks

Yassine Mebazaa: Integration of the IDR(s) Krylov Subspace Method into PETSc and Comparative Performance Analysis

SCCS Colloquium |

The efficient solution of large, sparse linear systems is a central problem in many fields of engineering and scientific computing. While direct methods such as Gaussian elimination or LU factorization are robust, they quickly become prohibitively expensive in terms of memory and computational cost for the increasing number of larger-scale problems. Iterative Krylov subspace methods have therefore become the de facto standard in such settings. However, due to the diversity of the different Krylov methods, choosing an appropriate one is highly dependent on the specific problem and available computational resources. In this thesis, we focus on the Induced imensionReductionmethodIDR(s), introduced by Sonneveld and van Gijzen (2008), which generalizes the original IDR method developed in 1980 by Wesseling and Sonneveld, and promises improved convergence behavior by constructing residuals within nested subspaces of decreasing dimension. Weimplemented IDR(s) as a new Krylov solver in the PETSc library, with careful attention to integration into its Krylov Subspace Solver (KSP)framework. This mainly consisted in writing the method according to the KSP interface, thus creating a new solver type that we called idrs. Our implementation was then benchmarked against widely used methods such as Conjugate Gradient Squared (CGS), GMRES, and BiCGStab, using a collection of real-world matrices from the SuiteSparse Matrix Collection. The experiments investigate both general robustness and performance as well as the influence of the shadow space dimensions and the choice of the shadow-space matrix P. The results show that IDR(s) is competitive with state-of-the-art Krylov solvers, even surpassing them in pure convergence rate over a set of general matrices. In many cases, moderate values of s (e.g., s = 4 or s = 8) provide a favorable trade-off between convergence speed and robustness. Furthermore, our experiments confirm several of the claims made in the original literature, such as the theoretical bound on convergence steps and the sensitivity to the conditioning of the small s × s systems. These findings support IDR(s) as a practical addition to PETSc for solving large, sparse linear systems in a black-box environment

Bachelor's thesis presentation. Yassine is advised by Hayden Liu Weng.

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Contribute a talk

To register and schedule a talk, you should fill the form Colloquium Registration at least four weeks before the earliest preferred date, at the end of a semester typically even earlier reservation is necessary due to a very high influx of presentations. Keep in mind that we only have limited slots, so please plan your presentation early! In special cases, contact colloquium(at)mailsccs.in.tum.de.

Colloquium sessions are now on-campus. We have booked room MI 02.07.023 for SS25 and MI 00.13.054 for WS25/26. You can either bring your own laptop or send us the slides as a PDF ahead of time. The projector only has an HDMI connection, so please bring your own adapters if necessary.

We invite students doing their Bachelor's or Master's thesis, as well as IDP, Guided Research, or similar projects at SCCS to give one 20min presentation to discuss their results and potential future work. The time for this is typically after submitting your final text. Check also with your study program regarding any requirements for a final presentation of your project work.

New: In regular times, we will now have slots for presenting early stage projects (talk time 2-10min). This is an optional opportunity for getting additional feedback early and there is no strict timeline.

Apart from students, we also welcome doctoral candidates and guests to present their projects.

During the colloquium, things usually go as follows:

  • 10min before the colloquium starts, the speakers setup their equipment with the help of the moderator. The moderator currently is Ana Cukarska. Make sure to be using an easily identifiable name in the online session's waiting room.
  • The colloquium starts with an introduction to the agenda and the moderator asks the speaker's advisor/host to put the talk into context.
  • Your talk starts. The scheduled time for your talk is normally 20min with additional 5-10min for discussion.
  • During the discussion session, the audience can ask questions, which are meant for clarification or for putting the talk into context. The audience can also ask questions in the chat.
  • Congratulations! Your talk is over and it's now time to celebrate! Have you already tried the parabolic slides that bring you from the third floor to the Magistrale?

Do you remember a talk that made you feel very happy for attending? Do you also remember a talk that confused you? What made these two experiences different?

Here are a few things to check if you want to improve your presentation:

  • What is the main idea that you want people to remember after your presentation? Do you make it crystal-clear? How quickly are you arriving to it?
  • Which aspects of your work can you cover in the given time frame, with a reasonable pace and good depth?
  • What can you leave out (but maybe have as back-up slides) to not confuse or overwhelm the audience?
  • How are you investing the crucial first two minutes of your presentation?
  • How much content do you have on your slides? Is all of it important? Will the audience know which part of a slide to look at? Will somebody from the last row be able to read the content? Will somebody with limited experience in your field have time to understand what is going on?
  • Are the figures clear? Are you explaining the axes or any other features clearly?

In any case, make sure to start preparing your talk early enough so that you can potentially discuss it, rehearse it, and improve it.

Here are a few good videos to find out more:

Did you know that the TUM English Writing Center can also help you with writing good slides?

Work with us!

Do your thesis/student project in Informatics / Mathematics / Physics: Student Projects at the SCCS.

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