A PERFORMANCE COMPARISON OF SCALAR, VECTOR, AND CONCURRENT VECTOR COMPUTERS INCLUDING SUPERCOMPUTERS FOR MODELING TRANSPORT OF REACTIVE CONTAMINANTS IN GROUNDWATER

Sophisticated and highly computation-intensive models of transport of reactive contaminants in groundwater have been developed in recent yea rs. Application of such models to real-world contaminant transport pro blems, e.g., simulation of groundwater transport of 10-15 chemically r eactive elements (e.g., toxic metals) and relevant complexes and miner als in two and three dimensions over a distance of several hundred met ers, requires high-performance computers including supercomputers. Alt hough not widely recognized as such, the computational complexity and demand of these models compare with well-known computation-intensive a pplications including weather forecasting and quantum chemical calcula tions. A survey of the performance of a variety of available hardware, as measured by the run times for a reactive transport model HYDROGEOC HEM, showed that while supercomputers provide the fastest execution ti mes for such problems, relatively low-cost reduced instruction set com puter (RISC) based scalar computers provide the best performance-to-pr ice ratio. Because supercomputers like the Cray X-MP are inherently mu ltiuser resources, often the RISC computers also provide much better t urnaround times. Furthermore, RISC-based workstations provide the best platforms for ''visualization'' of groundwater flow and contaminant p lumes. The most notable result, however, is that current workstations costing less than $10,000 provide performance within a factor of 5 of a Cray X-MP.