Gardens: An Integrated Programming Language and System for Parallel Programming Across Networks of Workstations

Gardens is an integrated programming language and system supporting parallel computation across networks of workstations. It addresses a combination of goals: it (i) maximises performance and (ii) is still safe, it supports (iii) the programming of abstractions (parallel libraries) and (iv) adaptive parallel computation, ie, computation that adapts at run-time to a changing set of available workstations. In Gardens , tasks represent units of work and task migration supports adaptation: releasing workstations on demand. To support adaptation, problems are over-decomposed into more tasks than processors. Tasking is non-preemptive: simplifying semantics and admitting a very eecient implementation. Within its local heap, each task manages a collection of global objects. These support: communication via global methods which other tasks may invoke, abstraction and typed safe asynchronous communication (including freedom from self-innicted and distributed network deadlocks). The implementation of global objects maps eeciently to high performance messaging layers, such as Active Messages.