Windowed multipole for cross section Doppler broadening

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• 作者：C. Josey ^{cjosey@mit.edu" class="auth_mail" title="E-mail the corresponding author} ; P. Ducru ^{p_ducru@mit.edu" class="auth_mail" title="E-mail the corresponding author} ; B. Forget ; ^{bforget@mit.edu" class="auth_mail" title="E-mail the corresponding author} ; K. Smith ^{kord@mit.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Monte Carlo ; Multipole ; Doppler broadening
• 刊名：Journal of Computational Physics
• 出版年：2016
• 出版时间：15 February 2016
• 年：2016
• 卷：307
• 期：Complete
• 页码：715-727
• 全文大小：832 K

文摘

This paper presents an in-depth analysis on the accuracy and performance of the windowed multipole Doppler broadening method. The basic theory behind cross section data is described, along with the basic multipole formalism followed by the approximations leading to windowed multipole method and the algorithm used to efficiently evaluate Doppler broadened cross sections. The method is tested by simulating the BEAVRS benchmark with a windowed multipole library composed of 70 nuclides. Accuracy of the method is demonstrated on a single assembly case where total neutron production rates and width="29" alt="View the MathML source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S002199911500532X-si1.gif">${}^{238}\mathrm{U}$ capture rates compare within 0.1% to ACE format files at the same temperature. With regards to performance, clock cycle counts and cache misses were measured for single temperature ACE table lookup and for windowed multipole. The windowed multipole method was found to require 39.6% more clock cycles to evaluate, translating to a 7.9% performance loss overall. However, the algorithm has significantly better last-level cache performance, with 3 fewer misses per evaluation, or a 65% reduction in last-level misses. This is due to the small memory footprint of the windowed multipole method and better memory access pattern of the algorithm.