From Design Patterns to Parallel Architectural Skeletons

The concept of design patterns has been extensively studied and applied in the context of object-oriented software design. Similar ideas are being explored in other areas of computing as well. Over the past several years, researchers have been experimenting with the feasibility of employing design-patterns related concepts in the parallel computing domain. In the past, several pattern-based systems have been developed with the intention to facilitate faster parallel application development through the use of preimplemented and reusable components that are based on frequently used parallel computing design patterns. However, most of these systems face several serious limitations such as limited flexibility, zero extensibility, and the ad hoc nature of their components. Lack of flexibility in a parallel programming system limits a programmer to using only the high-level components provided by the system. Lack of extensibility here refers to the fact that most of the existing pattern-based parallel programming systems come with a set of prebuilt patterns integrated into the system. However, the system provides no obvious way of increasing the repertoire of patterns when need arises. Also, most of these systems do not offer any generic view of a parallel computing pattern, a fact which may be at the root of several of their shortcomings. This research proposes a generic (i.e., pattern- and application-independent) model for realizing and using parallel design patterns. The term “parallel architectural skeleton” is used to represent the set of generic attributes associated with a pattern. The Parallel Architectural Skeleton Model (PASM) is based on the message-passing paradigm, which makes it suitable for a LAN of workstations and PCs. The model is flexible as it allows the intermixing of high-level patterns with low-level message-passing primitives. An object-oriented and library-based implementation of the model has been completed using C++and MPI, without necessitating any language extension. The generic model and the library-based implementation allow new patterns to be defined and included into the system. The skeleton-library serves as a framework for the systematic, hierarchical development of network-oriented parallel applications.