Development of an Expert System for Generating an Effective Mesh Distribution for the S_N Method in the Parallel Environment

摘要

An expert system for generating an effective mesh distribution for the S_N method is being developed. This expert system consists of two main parts: (a) an algorithm for generating an effective mesh distribution common for both serial and parallel calculations and (b) an algorithm for selecting an effective domain decomposition strategy for parallel computing. For the first part, the algorithm consists of four steps: creation of a geometric model and coarse meshes, calculation of un-collided flux, selection of differencing schemes, and generation of fine mesh distribution. A parallel code called PENFC (Parallel Environment Neutral-Particle First Collision) has been developed. It is capable of calculating uncollided flux and first collision sources for 3-D Cartesian geometry in a parallel environment. For the second part, an empirical parallel performance model is being developed. It accounts for memory requirement and parallel performance. We determine an effective domain decomposition strategy based upon the extent of coupling among domains and computation-to-communication ratio per iteration. The effective strategy is the one that minimizes coupling among processors and possesses high computation-to-communication ratio. To date, we have tested PENFC with PENTRAN using the simplified VENUS-3 model. PENFC yields a good agreement in the uncollided flux distribution as compared to PENTRAN. It also demonstrates good load balancing for parallel computing. Further our algorithm predicts PENTRAN differencing schemes up to 84% of coarse meshes. We are continuing our work to improve the performance of our algorithms for both serial and parallel computing.