The Illinois Concert System: Programming Support for Irregular Parallel Applications

Irregular applications are critical to supporting grand challenge applications on massively parallel machines and extending the utility of those machines beyond the scientiic computing domain. The dominant parallel programmingmodels, data parallel and explicit message passing, provide little support for programming irregular applications. We articulate a set of requirements for supporting irregular computations on massively parallel machines: a shared object namespace, integrated task and data parallelism, dynamic thread creation, and aggressive compiler and runtime support. We believe that any successful programming tools for irregular applications must provide these services. The Illinois Concert System provides these essential services in a concurrent object-oriented programming model, supporting data abstraction and convenient expression of irregular concurrency. Concert also provides program development and debugging tools helpful for developing explicitly concurrent programs. The basic features of the Concert system, programming model and tools, are described. Two application programs are used as examples, highlighting the utility of the system support for irregular applications. Preliminary performance numbers are reported.