Merlin conjures for Albert Einstein
Invitation for the launching of the supercomputer cluster MERLIN in the presence of the Brandenburg Minister of Science Prof. Johanna Wanka
on 2 July 2003, 12:00 pm. at the Max Planck Institute for Gravitational Physics (Foyer), Am Mühlenberg 1, 14476 Golm
The first direct detection of gravitational waves may be achieved at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in Potsdam-Golm. From now on the supercomputer cluster MERLIN is the worldwide fastest and only computer network at the disposal of the international scientific community that is exclusively devoted to the search for gravitational waves emitted by pulsars. MERLIN will search the gigantic data volumes generated by the German-British gravitational wave detector GEO600 and, in the context of international cooperation, also that of the American LIGO project.
Astrophysicists assume that the direct detection of gravitational waves will open up an entire new window to the universe: the observation of hitherto inaccessible aspects of the universe (black holes, dark matter, big bang).
Programme 2 July 2003
12:00 Greeting
Prof. Bernard Schutz, Managing Director at the Max Planck Institute for Gravitational Physics
12:05 Short welcoming speech
Prof. Johanna Wanka, Brandenburg Minister for Science and Culture
12:15 Merlin and the first science run of the GEO600 and LIGO gravitational wave detectors
Dr. Maria Alessandra Papa, Data Analysis Group Leader at the AEI
12:25 Launching of MERLIN
Background information
Gravitational waves and gravitational wave detectors
Gravitational waves are changes in the structure of space time that propagate at the speed of light. After the general theory of relativity has passed many tests with shining colours, it is especially this prediction of Albert Einstein that still awaits confirmation by direct proof.
Gravitational waves can be directly detected by means of highly sensitive laser interferometers. Currently five of these completely new types of telescopes are under construction: the German-British GEO600 project, which is overseen by the AEI, LIGO in the USA (two facilities), VIRGO in Italy and TAMA in Japan. The networking of the detectors is planned and has already been partially implemented. If gravitational waves could be measured, information would be obtained about the position of the source, as well as the time structure and direction of oscillations. Moreover, measurement errors can be avoided.
MERLIN
MERLIN scans data supplied by the detectors for signals of gravitational waves. The supercomputer cluster consists of 180 computer nodes, each with two AMD Athlon™ MP processors.
“We are proud that with MERLIN the Albert Einstein Institute now has the world’s fastest and only computer network dedicated exclusively to the search for gravitational waves emitted by pulsars. This is a decisive step that brings us closer to the observation of up-to-now inaccessible aspects of the universe. In particular, we would like to deeply thank the Brandenburg Ministry of Science for the trusting and smoothly operating cooperation!,” said Prof. Dr. Bernard F. Schutz, Managing Director at the Albert Einstein Institute.
“The special thing about MERLIN is that, unlike other parallel computers, its individual nodes independently examine the data for gravitational wave signals,” says Dr. Maria Alessandra Papa, who led the international work group that developed the design of the cluster. When designing the cluster, less importance was placed on fast communication between individual nodes. More important was that different nodes evaluate data independently of each other – and thus more effectively. This is made possible through special software developed at AEI that minimises communication between the nodes. The necessary network infrastructure can therefore be realised cost-effectively with standard elements.
Technical details
• MERLIN has 180 nodes, each with two AMD Athlon MP processors, 2200+ and 2600+.
• Peak performance: 1330 gigaflops (giga = billions; flops: floating operations per second).
• For comparison: in 1979 the Cray 1 had a performance of 0.16 gigaflops.
• Total storage capacity: 36 terabytes (TB) (1 TB = 1,012 gigabytes/GB). Since all data is stored twice (simple redundancy), a total of 18 TB is available for secure data storage. This means that GEO600 data traffic from approximately six months can be stored.
When GEO600 is running, up to 90 GB of data are sent daily to AEI via the Internet. A high-performance direct connection between the Computer Centre in Hannover (RRZN) and the Konrad-Zuse-Zentrum für Informationstechnik Berlin (ZIB) is planned for continuous operation of GEO600. This is where the data is stored until the AEI retrieves it for analysis. In parallel, cooperation partners at the University of Cardiff receive a copy of all data.
Financing of MERLIN
The total costs of MERLIN amount to ca. 300,000 €.
Of that amount, the federal state of Brandenburg financed around 44,700 €.
Interdisciplinary research at AEI: Simulation, measurement, data analysis
The detection of gravitational waves can only be achieved by close cooperation between different disciplines:
Experimental physicists are working at the Sub-Institute of AEI in Hannover. Together they build and operate the GEO600 gravitational wave detector and are responsible for data collection.
The Numerical Relativity Group at AEI in Potsdam-Golm is seeking to understand the origin of gravitational waves. For this reason they do simulations on supercomputers, e.g. collisions of black holes and neutron stars. These simulations provide insights into the possible form of the signals that GEO600 would record during passage of a gravitational wave. This enables a focused search for signals in the detector data.
This search for the proverbial needle in the haystack has been undertaken by the Golm Gravitational Waves Group. They develop the mathematical tools that make it possible to search the gigantic quantity of data for interesting signals. The mathematical algorithms are continuously optimized and adapted to the characteristics of the detector in order to increase the possibility of detecting gravitational waves. Around 100 scientists work together worldwide to analyse the data of GEO600 and LIGO. In addition to communicating over the Internet, they are connected by weekly telephone conferences. The experts meet twice a year to discuss questions of fundamental importance. Special topics are discussed in working meetings.
Cooperation between AEI and ZIB
For many years a very close and very successful research cooperation has existed between the Konrad-Zuse-Zentrum für Informationstechnik Berlin (ZIB) and the AEI. They cooperate in the following areas:
- 3D visualisation of complex simulation results,
- allocated data management in the GEO600 experiment,
- remote control of high-performance simulation programs,
- grid computing in the joint EU project "GridLab."
In all four project areas, the application know-how of the AEI is ideally complemented by ZIB’s expert knowledge in high-performance computing. Both institutes maintain very close contact. The technical collaboration in the secure storage of mass data in the ZIB data robot has been established through a cooperation agreement that regulates the use of hardware and software, as well as the associated personnel services.
Since its foundation in 1995, the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) has established itself as the leading institute for gravitational physics. At the institute scientists research the entire spectrum of general relativity, e.g. they devote themselves to developing a theory that combines quantum field theory and general relativity. Another area of their work involves the exploration of gravitational waves and black holes, as well as the numerical solution of Einstein’s equations. New mathematical methods are developed in order to deal with the enormous difficulties of relativity research. The focus of the experimental work is the development of gravitational wave detectors on earth and in space.
