A Language for Array and Vector Processors

Abstract

The scientific community has consistently demanded from computing machines an increase in the number of instructions executed per second. The latest increase has been achieved by duplication of arithmetic units for an array processor and the pipelining of functional units for vector processors. The high level programming languages for such machines have not benefited from the advances which have been made in programming language design and implementation techniques.A high level language is described in this paper which is appropriate for both array and vector processors and is defined without reference to the hardware of either type of machine. The syntax enables the parallel nature of a problem to be expressed in a form which can be readily exploited by these machines. This is achieved by using the data declarations to indicate the maximum extent of parallel processing and then to manipulate this, or a lesser extent, in the course of program execution. It was found to be possible to modify many of the structured programming and data structuring concepts for this type of parallel environment and to maintain the benefits of compile time and run time checking. Several special constructs and operators are also defined.The language offers to the large scale scientific computing community many of the advances which have been made in software engineering techniques while it exploits the architectural advances which have been made.

Parallel language developments in Europe: An overview

“…The approach used in designing the Actus language [9,10] was to consider the problem areas in which array and vector processors are used, and to isolate the relevant features of the problem area. The next step was to form the syntactic and semantic rules for these abstractions which would enable the parallelism of a problem to be expressed directly while at the same time trying to ensure that a compiler for these features could be implemented efficiently.…”

An APL Compiler for a Vector Processor

“…As might be expected, this process is very difficult and has met with only limited success. A second approach is to develop new programming languages with explicit parallel instructions [16]. The acceptance of new languages is slow, however, and this has the drawback of producing yet another programming language that is available on only a limited number of machines in a limited number of locations.…”

Simd language design using prescriptive semantics

“…The philosophy of Actus [6] is to associate an "extent of parallelism" -a set of indices of the processes which may be manipulated in parallel -with certain control structures. This results in the provision of a parallel while statement and a parallel if... then.., else statement.…”