NECP-X中角度与特征线并行的研究与实现

特征线方法在应用于全堆芯三维输运计算时面临着计算时间长、内存需求量大的问题，而大规模并行是最有效的解决办法。传统的并行策略是进行空间的区域分解，但当问题的几何规模较小时，其并行度有限，无法充分利用并行资源。本文在高保真物理计算程序NECP-X空间区域分解的基础上研究了角度和特征线的三重并行计算。为实现角度并行的负载平衡，采用了考虑权重的贪婪算法角度并行策略；为节省内存，在共享内存的并行模式下采用动态调度的分配方案实现特征线并行。数值结果表明，NECP-X中的角度和特征线并行效率较高，可在空间区域分解并行的基础上进一步扩大并行规模，提高计算速度。

Development and Application of Angle and Ray Parallel in NECP-X

Long computing time and abundant memory requirement are two most critical issues for the method of characteristics (MOC) when applied for the three-dimensional whole-core transport calculation. The massive parallel is an effective method to solve these problems. The traditional parallel strategy based on space decomposition is limited by its degree of parallelism when solving the smaller size problem, which means it can not take full advantage of parallel resources. In this paper, a multilevel parallel of angle and characteristic ray was developed based on the space parallel implemented in the high-fidelity neutronics code NECP-X. To get good load balance of angle parallel, a greedy algorithm was applied, and to save memory in the ray parallel, a dynamic scheduling feature within shared memory architectures was used. The numerical results show that the parallel efficiency of the angle and characteristic ray in NECP-X is high. And it further expands the parallel degree based on the special decomposition parallelism.