S/sub n/ transport calculations on vector and parallel processors

The transport of radiation from its source to the location of people or equipment gives rise to some of the most challenging of calculations. A problem may involve as many as a billion unknowns, each evaluated several times to resolve interdependence. Such calculations run many hours on a CRAY computer, and a typical study involves many such calculations. The DOT code, which solves transport problems in two space dimensions, can be vectorized and extended to three-dimensions. Plans are being made to extend it to parallel processors. Repeated analysis, recoding, and reanalysis was required to vectorize the procedures. Each major section of the code required a different technique. In some cases, the new procedures improved performance on a scalar IBM machine, while parallel coding was required in others. It is not clear what coding techniques and computer architectures will offer the best performance in the future. Only competition and experimentation will reveal that