Component specification in the Cactus Framework: The Cactus Configuration Language

Abstract

Component frameworks are complex systems that rely on many layers of abstraction to function properly. One essential requirement is a consistent means of describing each individual component and how it relates to both other components and the whole framework. As component frameworks are designed to be flexible by nature, the description method should be simultaneously powerful, lead to efficient code, and be easy to use, so that new users can quickly adapt their own code to work with the framework.In this paper, we discuss the Cactus Configuration Language (CCL) which is used to describe components ("thorns") in the Cactus Framework. The CCL provides a description language for the variables, parameters, functions, scheduling and compilation of a component and includes concepts such as interface and implementation which allow thorns providing the same capabilities to be easily interchanged. We include several application examples which illustrate how community toolkits use the CCL and Cactus and identify needed additions to the language.

GRHydro: a new open-source general-relativistic magnetohydrodynamics code for the Einstein toolkit

“…The utilities contained in Einstein toolkit, e.g., help manage components [48,49], build code and submit simulations on supercomputers [50,51], or provide remote debuggers [52] and post-processing and visualization interfaces for VisIt [53].…”

An Introduction to the Einstein Toolkit

“…They can be found in the top level thorn directory, using the *.ccl file name extension (Cactus Configuration Language, see [37] for extensive details).…”

“…Typically, these different parts are hosted at different repositories, with different version control systems, and are maintained by different groups. GetComponents [36,37] provides a unified way of downloading all of these components in a user-friendly way, hiding this complexity from the user.…”

Using GPU's to accelerate stencil-based computation kernels for the development of large scale scientific applications on heterogeneous systems

“…The flesh provides a framework for defining and parsing parameters, for scheduling work, interoperation between C, C++, F77, and F90, as well as interaction with other thorns. Thorns are described using a domain specific language (DSL) called the Cactus Configuration Language (CCL) [1]. The information in the CCL files includes the name of the implementation, the definition of functions and parameters, the schedule of the routines, and whether they require synchronization after execution, etc.…”