Parallel expression in the APL2 language

This paper reports on an investigation of parallel expression and execution in the current APL2 language. The study covers a historical, theoretical, and empirical viewpoint. The parallel nature of APL is traced from its foundations in the Iverson notation to current problems in executing APL on parallel hardware. The paper discusses features of the APL language and its current implementations that limit taking advantage of parallel expressions. A survey of related topics from the work on APL compilers is also included. Each APL2 language construct is examined for potential parallel expression. The operations are grouped based on the possible parallelism exhibited by each operation, and the possible implementation of each group is discussed. Three APL2 applications are explored to determine the actual parallelism expressed in “real” APL2 code. These applications are chosen from distinct areas: graphics, database systems, and user interactive systems. The actual data passed as arguments to every operation are dynamically examined, and the information is collected for analysis. The data are summarized and results of the study are discussed.