THE NAS PARALLEL BENCHMARKS

The Numerical Aerodynamic Simulation (NAS) Program, which is based at NASA Ames Research Center, is a large-scale effort to advance the state of computational aerodynamics. Specifically, the NAS organization aims &dquo;to provide the Nation’s aerospace research and development community by the year 2000 a highperformance, operational computing system capable of simulating an entire aerospace vehicle system within a computing time of one to several hours&dquo; (NAS Systems Division, 1988, p. 3). The successful solution of this &dquo;grand challenge&dquo; problem will require the development of computer systems that can perform the required complex scientific computations at a sustained rate nearly 1,000 times greater than current generation supercomputers can achieve. The architecture of computer systems able to achieve this level of performance will likely be dissimilar to the shared memory multiprocessing supercomputers of today. While no consensus yet exists on what the design will be, it is likely that the system will consist of at least 1,000 processors computing in parallel. Highly parallel systems with computing power roughly equivalent to that of traditional shared memory multiprocessors exist today. Unfortunately, for various reasons, the performance evaluation of these systems on comparable types of scientific computations is very difficult. Relevant data for the performance of algorithms of interest to the computational aerophysics community on many currently available parallel systems are limited. Benchmarking and performance evaluation of such systems have not kept pace with advances in hardware, software, and algorithms. In particular, there is as yet no generally accepted benchmark program or even a benchmark strategy for these systems

The NAS Parallel Benchmarks

A new set of benchmarks has been developed for the performance evaluation of highly parallel supercomputers. These benchmarks consist of five "parallel kernel" benchmarks and three "simulated application " benchmarks. Together they mimic the computation and data movement characteristics of large scale computational fluid dynamics applications. The principal distinguishing feature of these benchmarks is their "pencil and paper" specification --- all details of these benchmarks are specified only algorithmically. In this way many of the difficulties associated with conventional benchmarking approaches on highly parallel systems are avoided. 1 This author is an employee of NASA Ames Research Center 2 This author is an employee of Computer Sciences Corporation. This work is supported through NASA Contract NAS 2-12961. 3 This author is an employee of the Research Institute for Advanced Computer Science (RIACS). This work is supported by the NAS Systems Division via Cooperative Agreemen..

Interoperability in ServiceBased Communities

Abstract. Interoperability is a multifaceted problem caused by issues surpassing those of technological incompatibilities. The real interoperability challenges are stemming from various sources, such as organisational incompatibilities buried deeply into the structures of collaborating enterprises, architectural mismatches and defective assumptions about business application behaviour, or from the inherent properties of business collaboration models. To achieve interoperability in enterprise computing environments, the aspects of interoperability must be identified and their properties analysed. This paper studies interoperability issues in enterprise computing environments. Enterprise computing environments under analysis are based on Service Oriented Computing paradigm and enhanced with necessary infrastructure facilities. Several classes of causes for interoperability problems are identified and the mechanisms for overcoming the problems in these classes are briefly discussed.