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The Cactus Computational Toolkit is an open source problem solving environment designed for scientists and engineers. Its modular structure easily enables parallel computation across different architectures and collaborative code development between different groups. Cactus originated in the academic research community, where it was developed and used over many years by a large international collaboration of physicists and computational scientists.

Cactus is used by the physicists in the Numerical Relativity group of the Max Planck Institute for Gravitational Physics, Albert Einstein Institute (AEI) to numerically simulate extremely massive bodies, such as neutron stars and black holes. An accurate model of such systems requires a solution of the full set of Einstein's equations for general relativity - equations relating the curvature of spacetime to the energy distribution. The overall goal is to deliver accurate signal patterns of sources of gravitational waves which then can be matched against the data measured at the various gravitational wave detector interferometers around the world (eg. GEO600, LIGO, later on LISA).

Real-time Monitoring & Steering of Cactus Simulations

One of the tasks that we have been working on in the AstroGrid-D project was to improve the existing monitoring/steering/visualisation methods available in the Cactus Computational Toolkit and specifically make them grid-aware. Software modules have been enhanced in order to provide standard monitoring & steering functionality such as

  • user authentication based on standard X509 Grid certificates
  • a general overview about this simulation's parameters (executable name, parameter file, owner, run date and host, number of processors used, etc.)
  • runtime information such as the current iteration number and simulation time
  • access to stdout/stderr logfiles
  • online visualisation of intermediate simulation results (see left image below as an example)
All of these methods are available via a generic web interface where the Cactus simulation acts as a stand-alone HTTPS web server, and users can connect to it with a standard web browser of their own choice.

Online 2D visualisation embedded in a live Cactus simulation Homepage of the Numerical Relativity Cactus Portal

Cactus Web Portal

Another scientific result of our work in the AstroGrid-D project was the development of a Cactus web portal. The motivation behind this was to provide a common point of access for application-specific services to Cactus users, enabling them

  • to keep a better overview on Cactus simulations which they or their collaborators have done already (eg. by searching in a simulation metadata catalogue)
  • to monitor and steer Cactus simulations which are currently running on the Grid
  • to view dynamic metadata announced by running Cactus simulations, allowing for user-specific queries
  • to gather and present a history of nightly Cactus Integration Test results

The Cactus web portal uses standard web technologies such as RDF to store and manage simulation metadata and GridSphere as open-source portal framework.

A public Cactus User Portal is available on https://portal.cactuscode.org.
Also available is a Numerical Relativity Portal with personalised user access for physicists of the Numerical Relativity community; this portal, online under https://portal.aei.mpg.de, provides Cactus Integration Test results for the majority of non-public Cactus code modules which are used by the numerical relativists for their daily Cactus production runs.


Cactus as a Grid use case was developed within the AstroGrid-D project and in close collaboration with the D-MON project. Both projects are members of and funded by the German Grid Initiative D-Grid. The use case was designed and implemented by the eScience group at the Max Planck Institute for Gravitational Physics, Albert Einstein Institute (AEI).

If you are interested to learn more about Cactus on the Grid, have any suggestions or want to provide feedback, please contact AEI's eScience group via its mailing list eScience(at)aei. mpg.de.