The increasing availability and use of supercomputers has highlighted the need for better software development techniques and tools. Supercomputers have traditionally been extensively used by engineers and scientists whose preference for Fortran is well established and recognized. However, in the parallel environment offered by the latest configurations of supercomputers, more sophisticated languages and tools are required. The present experiment is concerned with devising a syntax-directed integrated programming environment based on the language Actus, which enables a user to develop and debug programs before submitting them to an actual supercomputer. Actus is a high-level, Pascal-like language, with SIMD parallel processing features. It enables the user to ignore the idiosyncrasies of the chosen supercomputer by abstracting the parallel processing detail to a higher level. The editing, compilation and testing phases of program development are all integrated, providing a single consistent interface for all activities relating to program development.KEY WORDS Supercomputers Integrated programming environment Syntax directed editing Actus Cray (i) The defection of parallelism approach, in which languages such as sequential Fortran are examined to detect which parts of the program can be executed on the parallel hardware. This has been a successful approach and has been one of the dominant factors in the commercial success of supercomputers. However, there are disadvantages in that the user must write an algorithm 'Present address: Department Of Applied Computing, University Of Ulster At Magee. Londonderry BT48 7JL. Northern Ireland, U.K.
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PreprocessorEditor + ofthe program ' Semantlc Analyser in a sequential notation and may not therefore exploit the full parallelism of the machine. (ii) the expression of machine parallelism approach, in which the user expresses the algorithm in a notation which directly reflects the underlying parallel architecture. This facilitates the mapping of high-level code onto the architecture with particular benefits for code generation. However such languages are specific to one particular machine and are not therefore appropriate as general purpose supercomputer programming languages. (iii) the expression of problem parallelism approach, in which the user expresses the algorithm using a parallel notation which is independent of any detection mechanism or machine architecture; it represents the concept of abstract programming as applied to parallel machines. Aspects of this approach are apparent in the latest proposals for Fortran 8X.* This experiment favours the last approach for designing a programming language for supercomputers and aims to develop a syntax directed integrated programming environment for the parallel processing language Actw3.The next sections introduce the design and implementation details of the Actus programming environment. The language Actus is summarized in the Appendix.
