The KAP Parallelizer for DEC Fortran and DEC C Programs

The KAP preprocessor optimizes DEC Fortran and DEC C programs to achieve their best performance on Digital Alpha systems. One key optimization that KAP performs is the parallelization of programs for Alpha shared memory multiprocessors that use the new capabilities of the DEC OSF/1 version 3.0 operating system with DECthreads. The heart of the optimizer is a sophisticated decision process that selects the best loop to parallelize from the many loops in a program. The preprocessor implements a robust data dependence analysis to determine whether a loop is inherently serial or parallel. In engineering a high-quality optimizer, the designers specified the KAP software architecture as a sequence of modular optimization passes. These passes are designed to restructure the program to resolve many of the apparent serializations that are artifacts of coding in Fortran or C. End users can also annotate their DEC Fortran or DEC C programs with directives or pragmas to guide KAP's decision process. As an alternative to using KAP's automatic parallelization capability, end users can explicitly identify parallelism to KAP using the emerging industry-standard X3H5 directives.