A Graphical Retargetable Parallel Programming Environment and Its EfficientImplementation (dissertation)

This dissertation addresses the problem of facilitating the development of efficiently executing programs for multiple-instruction multi-datastream (MIMD) parallel computers. The family of MIMD parallel computer architectures is the most flexible and most widely applicable means of meeting requirements for very high performance computation. It is widely accepted, however, that current methods of preparing programs for these systems are inadequate and are the primary bottleneck for attainment of these machines'' potential. It is difficult to write programs which are both correct and efficient even for a single MIMD parallel architecture. A program which is efficient in execution on one member of this architecture class is often either not portable at all to different members of the architecture class, or if portability is possible, the efficiency attained is usually not satisfactory on any architecture. The conceptual basis of the approach we have taken to providing a solution for the problem of programming MIMD parallel architectures is based upon raising the level of abstraction at which parallel program structures are expressed and moving to a compositional approach to programming. The CODE 2.0 model of parallel programming permits parallel programs to be created by composing basic units of computation and defining relationships among them. It expresses the communication and synchronization relationships of units of computation as abstract dependencies. Runtime determined communications structures can be expressed. Ready access to these abstractions is provided by a flexible graphical interface in which the user can specify them in terms of extended directed graphs. Both ease of preparation of correct programs and compilation to efficient execution on multiple target architectures is enabled. The compositional approach to programming focuses the programmer''s attention upon the structure of the program, rather than development of small unit transformations. In the CODE 2.0 system, the units of computation are prepared using conventional sequential programming languages along with declaratively specified conditions under which the unit is enabled for execution. The system is built upon a unique object-oriented model of compilation in which communication and synchronization mechanisms are implemented by parameterized class templates which are used to custom tailor the translation of abstract specifications in communication and synchronization to efficient local models. The attainment of the goals of the research is measured in the following ways. There have been several uses of the CODE 2.0 system by casual users in parallel programming classes. The results are uniformly positive; the programs which are developed are simple and easy to read, and execute at least as efficiently as programs written in conventional parallel languages. Experimental measurement of the execution behavior of benchmark programs has shown that the executable code generated