On the use of tally servers in Monte Carlo simulations of light-water reactors

¹ Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 77 Massachusetts Avenue, Cambridge, MA 02139
² Argonne National Laboratory, Theory and Computing Sciences, 9700 S Cass Ave., Argonne, IL 60439

^* Corresponding Author, E-mail: paul.k.romano@gmail.com

Abstract

An algorithm for decomposing tally data in Monte Carlo simulations using servers has recently been proposed and analyzed. In the present work, we make a number of refinements to a theoretical performance model of the tally server algorithm to better predict the performance of a realistic reactor simulation using Monte Carlo. The impact of subdividing fuel into annular segments on parameters of the performance model is evaluated and shown to result in a predicted overhead of less than 20% for a PWR benchmark on the Mira Blue Gene/Q supercomputer. Additionally, a parameter space study is performed comparing tally server implementations using blocking and non-blocking communication. Non-blocking communication is shown to reduce the communication overhead relative to blocking communication, in some cases resulting in negative overhead.