Traversal recursion is a class of recursive queries where the evaluation of the query involves traversal of a graph or a tree. This limited type of recursion arises in many applications.In this report we investigate a simple file structure that efficiently supports traversal recursion over large, acyclic graphs. The nodes of the graph are sorted in topological order and stored in a B-tree. Hence, traversal of the graph can be done in a single scan. Nodes and edges can also be inserted, deleted, and modified efficiently.

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We analyze the costs, and describe the implementation, of three hashed-based join algorithms for a general-purpose shared-memory multiprocessor. The three algorithms considered are the Hashed Loops, GRACE and Hybrid algorithms. We also describe the results of a set of experiments which validate the cost models presented and demonstrate the relative performance of the three algorithms.

Our goal is to ease the parallelization of applications on distributed-memory parallel processors. Part of our team is implementing parallel kernels common to industrially significant applications using High Performance Fortran (HPF) and the Message Passing Interface (MPI). They are assisted in this activity by a second group developing an integrated tool environment, Annai, consisting of a parallelization support tool, a debugger, and a performance monitor and analyzer. These two groups interact closely, with application developers defining requirements and evaluating prototypes of the tool environment.The Annai environment is unique in providing a suite of generalpurpose tools for scientific application development, encompassing comprehensive support for programming irregular problems and the debugging and tuning of HPF and/or MPI-based parallel programs. Addressing application developer requirements, while making leading-edge technology available in a genuinely-usable form, has resulted in the timely provision of powerful parallel programming tools. This paper describes goals, achievements and perspectives of the project, illustrating with specific case studies of three application kernels how the tool environment assists in the parallelization process: development effort and resulting performance are discussed.