CAREER: An Integrated Approach for Improving the Performance, Programmability, and Portability of Shared Memory Multiprocessors

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While shared-memory multiprocessors simplify many aspects of programming, it is widely believed that naive shared- momory programs are not likely to result in high performance on most shared-memory systems. The broad objective is to develop and evaluate techniques for improving the performance of shared- memory systems while simultaneously enhancing programmability and portability. A key problem that inhibited performance in shared-memory systems is that, unlike message passing programs, the exact communication requirements of shared-memory programs are not obvious. Therefore, compilers, runtime systems, and hardware typically need to make conservative assumptions, resulting in excessive communication and synchronization primitives provided on a particular machine (e.g., locks and barriers), the intended sharing behavior is obscured by these details. Furthermore, the low-level primitives that must be used to obtain good performance vary from platform to platform, thus inhibiting program portability. This research takes an integrated approach to improving the performance, and portability of systems. The approach broadly is: (1) to identify common implementation-independent communication patterns along with primitive to express those patterns in a programming language, (2) to develop heuristics that can be used by the compiler, runtime systems, hardware or some combination thereof to map these high-level primitives to the appropriate low-level primitives supported by the particular target system, and (3) to evaluate the resulting performance benefits on the system. By exposing the intended sharing behavior, many instances of unnecessary communication should be avoided, thus achieving higher performance. Furthermore, despite the larger variety of synchronization patterns that a programmer must choose from his or her task is simplified because details of implementing the patterns are left to the programming support system (note tha t the sharing patterns themselves must be understood by the programmer anyway). Finally, in combination with other projects within the overall research program, this research should demonstrate that these common, high-level synchronization patterns can be efficiently supported on a variety of platforms, thus enhancing the portability of the program. This part of the research program is focused on investigating a specific kind of target system - a hardware distributed shared- memory multiprocessor that provides software control for protocols and efficient active message support (e.g., Stanford Flash and Wisconsin Typhoon)- using execution-driven simulation. Other projects in this research program are already exploring similar issues on other types of target systems. Education: The educational objectives fall within three broad areas: curriculm development, teaching methods, and education outside the classroom. The objectives of the curriculm development part are (1) to introduce a course in parallel computing involving computational scientists and engineers along with computer scientists (both in terms of students attending and faculty teaching the course), (2) to introduce hands-on parallel programming experience as part of currently existing undergraduate computer architecture course, (3) to impart a sound education on performance analysis techniques, and (4) to impart a research experience to undergraduates by having a modest research project as part of the senior level architecture course and by actively recruiting undergraduates in the proposed research program through the Rice senior honor's thesis program. The teaching methods part of the education plan address growth as an effective teacher by exposure to research in teaching methods. The final part seeks to (1) encourage women and other under- represented groups to pursue computer science by actively interacting with such groups informally and through formal workshops, and (2) encourage an ex change between industry and academia through tutorials and short courses.