This paper introduces hierarchical overlapped tiling, a transformation that applies loop tiling and fusion to conventional loops. Overlapped tiling is a useful transformation to reduce communication overhead, but it may also generate a significant amount of redundant computation. Hierarchical overlapped tiling performs overlapped tiling hierarchically to balance communication overhead and redundant computation, and thus has the potential to provide better performance.

Grid computing provides a very rich environment for scientific calculations. In addition to the challenges it provides, it also offers new opportunities for optimization. In this paper we have utilized DFS (distributed file streaming) framework to speed up NAS grid benchmark workflows. By studying I/O patterns of NGB codes we have identified program locations where it is possible to overlap computation and data workflow phases. By integrating DFS into NGB, we demonstrate a useful method of improving overall workflow efficiency by streaming the output of the current process to make an input of the following stage, reducing a workflow to a series of distributed producer consumer stages. DFS framework eliminates file transfers and in the process makes process scheduling more efficient, leading to overall performance improvements in the turnaround time for HC (helical chain) data flow graph under Globus grid environment with the embedded DFS over the original version of the benchmark

With modern massively parallel processors consisting of hundreds of RISC (reduced instruction set computer) processors, a significant portion of program run time is being spent in passing messages between processors. The authors address the problem of reducing unnecessary copies in message passing protocols. Message passing that avoids using copies in the application program and the transport mechanism is called low copy message passing. The authors describe the low copy message passing library on the Alliant CAMPUS/800 system. First, a way to reduce the number of copies in a message passing protocol is proposed. In gross machine independent terms, the message passing protocol can be reduced from seven major steps to one. The authors then describe how application programmers can use the low copy message passing library. Finally, a brief survey of applications is presented which shows how applications use the low copy library.>

Dependence graphs can be used as a vehicle for formulating and implementing compiler optimizations. This paper defines such graphs and discusses two kinds of transformations. The first are simple rewriting transformations that remove dependence arcs. The second are abstraction transformations that deal more globally with a dependence graph. These transformations have been implemented and applied to several different types of high-speed architectures.

In this paper, we consider the problem of restructuring or transforming algorithms to efficiently use a single-stage interconnection network. All algorithms contain some freedom in the way they are mapped to a machine. We use this freedom to show that superior interconnection efficiency can be obtained by implementing the interconnections required by the algorithm within the context of the algorithm rather than attempting to implement each request individually. The interconnection considered is the bidirectional shuffle-shift. It is shown that two algorithm transformations are useful for implementing several lower triangular and tridiagonal system algorithms on the shuffle-shift network. Of the 14 algorithms considered, 85% could be implemented on this network. The transformations developed to produce these results are described. They are general-purpose in nature and can be applied to a much larger class of algorithms.