Structuring parallel algorithms in an MIMD, shared memory environment

Abstract This paper discusses the class of algorithms having global parallelism, i.e. those in which parallelism is introduced at the top of the program structure hierarchy. Such algorithms have performance advantages in a shared-memory. MIMD computational model. A programming environment consisting of FORTRAN, enhanced by some pre-processed macros, has been built to aid in writing programs for such algorithms for the Denelcor HEP multiprocessor. Applications of from tens to hundreds of FORTRAN statements have been written and tested in this environment. A few parallelism constructs suffice to yield understandable programs with a high degree of parallelism. The automatic generation of programs with global parallelism seems to be a promising possibility.