ZIH-Colloquium

The ZIH colloquium is a public event and takes place on each 4th Thursday of the month at 15:00 o'clock in the room Willers-Bau A 317.
For additional or extraordinary events time and room are explicitly mentioned.

Next Colloquium

Divergent date: 20. April 2017, 15:00 Phil Carns (Argonne National Laboratory) "Characterizing HPC I/O: from Applications to Systems"
Scientific computing applications are becoming increasingly data-intensive in fields as diverse as biology, physics, and materials, and the computing facilities that support them are deploying increasingly complex storage technologies in order to meet demand. It is therefore more important than ever to understand the I/O behavior of applications as well as systems so that the community can implement effective optimizations, guide best practices, and procure more productive systems. This seminar will highlight recent advancements in understanding HPC I/O the context of Darshan, a widely-used application-level I/O characterization tool. This includes new mechanisms to vary the fidelity of instrumentation as well as new mechanisms to facilitate the correlation of application data with other forms of instrumentation. We will then highlight the broader TOtal Knowledge of I/O (TOKIO) project, a joint effort between Lawrence Berkeley Laboratory and Argonne National Laboratory, which seeks to leverage not only application-level instrumentation but component-level and system-level instrumentation to form a coherent, holistic view of I/O behavior. TOKIO integrates, correlates, and analyzes a diverse collection of data to produce actionable insight that interprets I/O performance in a broader system and historical context.
Philip Carns is a principal software development specialist in the Mathematics and Computer Science Division of Argonne National Laboratory, an adjunct associate professor of electrical and computer engineering at Clemson University, and a fellow of the Northwestern-Argonne Institute for Science and Engineering. His research interests in data-intensive scientific computing include characterization of storage systems, development of specialized data services, and simulation of storage architectures.

Further Colloquia

Divergent date: 15. Mai 2017, 15 Uhr Steffen Rulands (MPI PKS, Dresden)

Past Colloquia

16. February 2017: Thomas Ihle (Ernst-Moritz-Arndt University Greifswald,
Institute for Physics) "Kinetic theory of active matter: coarse-graining and invasion waves"

Models of self-driven agents similar to the Vicsek model are studied by means of kinetic theory. In these models, particles try to align their travel directions with the average direction of their neighbors plus some noise. At low noise, a globally ordered state of collective motion forms. These models have a discrete time step, consist of a simple streaming and collision step and are easily implemented on a computer.
A kinetic theory is derived from an exact equation for the N-particle probability density using Boltzmann’s approximation of Molecular Chaos. A coarse-graining procedure, called Chapman-Enskog expansion is performed to derive hydrodynamic equations from the kinetic theory.
The kinetic theory is also solved numerically by a Lattice-Boltzmann-like algorithm. Steep soliton-like waves are observed that lead to an abrupt jump of the global order parameter if the noise level is changed. The shape of the waves is shown to quantitatively agree within 3% with agent-based simulations at large particle speeds. At small densities and realistic particle speeds, the mean-field assumption of Molecular
Chaos is invalid near the onset of collective motion, and correlation and memory effects become relevant.
I will show how to self-consistently include correlation effects at the level of ring-kinetic theory. Instead of just one kinetic equation, an additional equation for the time evolution of the two-particle correlations will be derived. This equation is solved numerically for a homogeneous system and shown to be in excellent agreement with agent-based simulations in certain parameter ranges.
Thomas Ihle studierte Physik an der Universität Leipzig, wechselte 1991 als Diplomand an das Forschungszentrum Jülich und promovierte 1996 an der RWTH Aachen. Nach Postdoc-Aufenthalten in Paris, Grenoble, Minneapolis und Stuttgart wurde Prof. Ihle 2004 an die North Dakota State University berufen, wo er 2010 Tenure erhielt. 2015 erfolgte die Ernennung zum Professor an der Ernst-Moritz-Arndt Universität Greifswald. Hauptarbeitsgebiete sind kinetische Theorie und Computersimulation selbstgetriebener Teilchen, Entwicklung teilchenbasierter Algorithmen für komplexe Flüssigkeiten sowie Musterbildung beim Kristallwachstum.

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Last modified: Apr 05, 2017