DPOS: A metalanguage and programming environment for parallel processors

The complexity and diversity of parallel programming languages and computer architectures hinders programmers in developing programs and greatly limits program portability. All MIMD parallel programming systems, however, address common requirements for process creation, process management, and interprocess communication. This paper describes and illustrates a structured programming system (DPOS) and graphical programming environment for generating and debugging high-level MIND parallel programs. DPOS is a metalanguage for defining parallel program networks based on the common requirements of distributed parallel computing that is portable across languages, modular, and highly flexible. The system uses the concept of stratification to separate process network creation and the control of parallelism form computational work. Individual processes are defined within the process object layer as traditional single threaded programs without parallel language constructs. Process networks and communication are defined graphically within the system layer at a high level of abstraction as recursive graphs. Communication is facilitated in DPOS by extending message passing semantics in several ways to implement highly flexible message passing constructs. DPOS processes exchange messages through bi-directional channel objects using guarded, buffered, synchronous and asynchronous communication semantics. The DPOS environment also generates source code and provides a simulation system for graphical debugging and animation of the programs in graph form.