ZIH-Colloquia 2021
23rd September 2021, 16:00 MESZ, ONLINE-Video-Conference:
Christian Trott (Sandia National Laboratories, Albuquerque, USA) -
"The Manycore Revolution: An Eyewitness Account"
When CUDA was released in 2006, allowing for general purpose programming of graphics processing units, it wasn't obvious that it is a harbinger of things to come. In hindsight however it marks the start of an unprecedented explosion in computer architecture innovation, which does not appear to stop anytime soon. This talk retraces one part of that computational revolution: how a statistical physics student from as small German university ended up leading Kokkos, one of the central software technology projects at the US National Labs dealing with that computational revolution.
This Kokkos EcoSystem is a software stack which enables comprehensive performance portability for high performance computing applications. Developed by a team from five US National Laboratories as well as other partners, it is now used by an estimated 200 projects from around the world. Within the US Exascale Computing Project, nearly as many applications have a dependency on Kokkos now as on Fortran. The talk will dive into what makes the Kokkos project special, will discuss how Kokkos became successful and how CoDesign efforts with the hardware vendors was a crucial part of that. Additionally some thoughts about the future of the HPC computing landscape will be presented: what kind of changes we might expect in the next decade, and how Kokkos fits into that future.
Christian Trott is a high performance computing expert with extensive experience designing and implementing software for modern HPC systems. He is a principal member of staff at Sandia National Laboratories, where he leads the Kokkos core team developing the performance portability programming model for C++ and heads Sandia's delegation to the ISO C++ standards committee. He also serves as adviser to numerous application teams, helping them redesign their codes using Kokkos and achieve performance portability for the next generation of supercomputers. Christian earned a doctorate from the University of Technology Ilmenau in theoretical physics with a focus on computational material research.
26th August 2021, 16:00 MESZ, ONLINE-Video-Conference:
Hartmut Kaiser (Stellar Group, Louisiana State University, USA) -
"Towards a standard C++ asynchronous programming model" (Folien)
With the advent of modern computer architectures characterized by -- amongst other things -- many-core nodes, deep and complex memory hierarchies, heterogeneous subsystems, and power-aware components, it is becoming increasingly difficult to achieve best possible application scalability and satisfactory parallel efficiency. The community is experimenting with new programming models that rely on finer-grain parallelism, and flexible and lightweight synchronization, combined with work-queue-based, message-driven computation. The recently growing interest in the C++ programming language in industry and in the wider community increases the demand for libraries implementing those programming models for the language.
In this talk, we present a new asynchronous C++ parallel programming model that is built around lightweight tasks and mechanisms to orchestrate massively parallel (and -- if needed -- distributed) execution. This model uses the concept of (Standard C++) futures to make data dependencies explicit, employs explicit and implicit asynchrony to hide latencies and to improve utilization, and manages finer-grain parallelism with a work-stealing scheduling system enabling automatic load balancing of tasks.
Hartmut Kaiser is a member of the faculty at Louisiana State University (LSU) and a senior research scientist at LSU's Center for Computation and Technology (CCT). He is probably best known through his involvement in open source software projects, mainly as the author of several C++ libraries he has contributed to Boost, which are in use by thousands of developers worldwide. His current research is focused on leading the STE||AR group at CCT working on the practical design and implementation of future execution models and programming methods. He is a voting member of the C++ standardization committee.
24th June 2021, 15:00 MESZ, ONLINE-Video-Conference:
Markus Schmidtchen (TU Dresden, Institut für Wissenschaftliches Rechnen) -
"Emergentes Verhalten und Musterbildung in Systemen von Aggregations-Diffusions-Gleichungen"
Travelling pulses of bacteria, pigment cells, whole patches of tissue, flocks of birds, fish schools, or even pedestrians — non-locally interacting species are ubiquitous in nature. Compared to single species models, which have been studied quite intensively, corresponding two species models have only recently gained considerable attention. Often, it is possible to observe and model simple behavioural rules between two (indistinguishable) individuals based on biological or social forces. These interactions between any two individuals are typically referred to as first principles, for these interaction principles lead to very rich and complex behaviours as soon as many individuals are involved.
In the first part of the talk we propose a non-local model for two interacting species and discuss pattern formation and phase segregation effects. Albeit a toy model, the model poses quite a few analytical challenges which we shall briefly touch upon. We conclude the seminar by discussing applications of the model to tissue growth and to skin-patterning in zebrafish.
Markus Schmidtchen’s research interests revolve around the study of interacting species including modelling aspects and analytical aspects, alike. In 2019 he received his PhD from Imperial College London for his study on “A Study of Systems of Two Cross-Interacting Species” under the supervision of Prof. Dr. José A. Carrillo de la Plata. In 2019, he was accepted as a postdoctoral fellow by the Fondation Sciences Mathématiques de Paris and hosted at LJLL, Sorbonne Université, Paris, by Prof. B. Perthame where he was working on rigorous links between density-based models and geometric free-boundary models of tissue growth. In October 2020 he was inaugurated as Junior-Professor for Applied Mathematics at the Institute of Scientific Computing, TU Dresden.