Annual Report 2010 - Fachgruppe Informatik an der RWTH Aachen ...

Aachen Institute for Advanced Study in Computational Engineering Science (AICES)
Funded by Deutsche Forschungsgemeinschaft (DFG).
AICES is a doctoral program established under the auspices of the Excellence Initiative of the
German state and federal governments to meet the future research challenges in
computational engineering science. Currently, two members of our group conduct their thesis
projects funded through AICES Ph.D. fellowships. One thesis project examines the timedependent
behavior of parallel applications and aims at making the performance analysis
more scalable with respect to the length of execution. To be able to apply a previously
devised algorithm for the semantic compression of time-series call-path profiles also to C++
codes, where direct instrumentation may cause inacceptably high overhead, a hybrid profiling
technique was developed that captures key communication metrics via direct instrumentation,
while user-code profiling is accomplished via low-overhead sampling. The other project
investigates load and communication imbalance in parallel codes to better understand the
formation of performance-degrading wait states. First, a terminology was introduced to
classify wait states based on their propagation behavior. Building on earlier work by Meira,
Jr. et al., a scalable method was then designed that identifies program wait states, classifies
them according to the above-mentioned terminology, and attributes their cost in terms of
resource waste to their original cause. By replaying event traces in parallel, it is now possible
to identify the processes and call paths responsible for the most severe waiting times even for
runs with very large numbers of processes. This work won the best paper award of the
International Conference on Parallel Processing (ICPP) 2010 in San Diego, California.
Virtual Institute – High Productivity Supercomputing (VI-HPS)
Funded by the Helmholtz Association and carried out in cooperation with Forschungszentrum
Jülich, RWTH Aachen University (Institute for Scientific Computing), TU Dresden,
University of Tennessee, TU Munich, and University of Stuttgart.
The mission of this virtual institute is to improve the quality and accelerate the development
process of complex simulation programs in science and engineering that are being designed
for the most advanced parallel computer systems. For this purpose, we develop and integrate
state-of-the-art programming tools for high-performance computing that assist domain
scientists in diagnosing programming errors and optimizing the performance of their
applications. In these efforts, we place special emphasis on scalability and ease of use.
Besides the purely technical development of such tools, the virtual institute also offers
training workshops with practical exercises to make more users aware of the benefits they can
achieve by using the tools. During the past year, three tuning workshops with hands-on
sessions were organized in Munich, Amsterdam, and the King Abdullah University of Science
and Technology in Saudi Arabia. In addition, two conference tutorials also with hands-on
exercises were held at the IEEE Conference on Cluster Computing in Heraklion, Greece and
at the ACM/IEEE Conference on Supercomputing (SC10) in New Orleans, USA.
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