A large number of applications from information processing as well as science and engineering require processing large amounts of data. Particularly, in the science and engineering domain, the so called ``grand challenge applications'' fall in this category. Thus, it has become apparent that I/O performance much more than CPU or communication performance may be the limiting factor in future parallel computing systems. Many software and hardware components play a key role in I/O operations and any one of them can cause severe bottlenecks. The disparity between the performance of disk systems and CPU (and interconnect) performance requires the use of large-scale parallelism (and supporting software) to address the scalability and performance problems in I/O subsystems. But parallelism in the I/O systems introduces complexities for the system software including compilers, runtime systems and file systems. This research addresses many system software problems in the parallel I/O domain. To ameliorate the I/O bottlenecks, the following are necessary: 1) techniques for sophisticated runtime systems that incorporate the notion of collective I/O, data reuse and prefetching; 2) compiler analysis to identify various optimizations including data access reorganization, opportunities for overlapping computations and I/O, and data staging to handle limited memory for out-of-core computations; and 3) file systems optimizations to recognize collective access patterns for coordinating accesses of processes that are part of parallel programs, and using these access patterns for prefetching, buffer allocation and replacement strategies. Traditional interfaces for file systems lack the necessary semantics to permit the above optimizations. Thus, it is necessary to develop interfaces between the compiler and the runtime systems, and the runtime system and the file systems, that facilitate the flow of semantic information about access patterns to enable optimizations. This res earch pursues the design and development of techniques for compiler analysis, mechanisms and algorithms for runtime systems, and interfaces and optimizations for file systems to enable high- performance I/O in parallel computers. These techniques are being evaluated by implementing them on parallel systems. ***
