No abstract available.

Fully vectorized versions of the Los Alamos National Laboratory benchmark code Gamteb, a Monte Carlo photon transport algorithm, were developed for the Cyber 205/ETA-10 and Cray X-MP/Y-MP architectures. Single-processor performance measurements of the vector and scalar implementations were modeled in a modified Amdahl's Law that accounts for additional data motion in the vector code. The performance and implementation strategy of the vector codes are related to architectural features of each machine. Speedups between fifteen and eighteen for Cyber 205/ETA-10 architectures, and about nine for CRAY X-MP/Y-MP architectures are observed. The best single processor execution time for the problem was 0.33 seconds on the ETA-10G, and 0.42 seconds on the CRAY Y-MP.

A fully vectorized version of a one-dimensional Monte Carlo algorithm applied to molecular aerodynamics is presented. The algorithm is applied to the Rayleigh problem, an impulsively accelerated, heated flat plate, and is implemented on the CYBER 205. Issues relating to the details of vectorization, including the use of bit addressability, the maintaining of long vector lengths, and vector gather/scatter use, are discussed. Speedup factors due to vectorization in the range of 5 to 18 are reported, depending on problem parameters. The results indicate that under certain circumstances, the problem performs well on vector architectures.>