In this report we specify HPF+, a language supporting the execution of advanced applications on scalable parallel architectures. HPF+ is an extension of Fortran 90/95 and based upon Vienna Fortran, Vienna Fortran 90, and High Performance Fortran (HPF-1). It was developed in the ESPRIT project HPF+ (see http://www.par.univie.ac.at/hpf+), in close connection with the HPF-2 standardization effort. HPF+ serves as the base language for the priority research project "AURORA" of the Austrian Science Fund (http://www.vcpc.univie.ac.at/aurora). In order to provide adequate support for complex industrial and academic applications, HPF+ extends the data distribution features of HPF-1 by introducing new mechanisms which are applicable to irregular data structures. The handling of processors has been clarified and generalized in order to enable the distribution of arrays of different rank to the same processors and to influence load balancing. The concept of independent loops has been extended in order to reflect the requirements of the benchmark codes which are characterized by highly irregular access patterns. This includes mechanisms to influence the distribution of loop iterations, to specify reduction operations and re-usable communication schedules, and to avoid communication overheads caused by calls to procedures from within such loops. A number of ill-defined concepts of HPF-1 have been redesigned or eliminated. In particular, the data distribution model and the argument transfer mechanisms have been significantly simplified without the loss of required functionality.

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