In recent years, the prospects of performing fundamental and applied studies at the next-generation high-intensity laser facilities have greatly stimulated the interest in performing large-scale simulations of laser interaction with matter with the account for quantum electrodynamics (QED) processes such as emission of high energy photons and decay of such photons into electron-positron pairs. These processes can be modeled via probabilistic routines that include frequent computation of synchrotron functions and can constitute significant computational demands within accordingly extended Particle-in-Cell (QED-PIC) algorithms. In this regard, the optimization of these routines is of great interest. In this paper, we propose and describe two modifications. First, we derive a more accurate upper-bound estimate for the rate of QED events and use it to arrange local sub-stepping of the global time step in a significantly more efficient way than done previously. Second, we present a new high-performance implementation of synchrotron functions. Our optimizations made it possible to speed up the computations by a factor of up to 13.7 depending on the problem. Our implementation is integrated into the PICADOR and Hi-Chi codes, the latter of which is distributed publicly (https://github.com/hi-chi/pyHiChi).

中文翻译：

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QED-PIC 代码中事件生成器的优化例程

近年来，在下一代高强度激光设施中进行基础和应用研究的前景极大地激发了人们对利用量子电动力学 (QED) 过程进行大规模激光与物质相互作用模拟的兴趣，例如高能光子的发射和这些光子衰变成电子-正电子对。这些过程可以通过概率例程建模，其中包括同步加速器函数的频繁计算，并且可以在相应扩展的细胞内粒子 (QED-PIC) 算法中构成重要的计算需求。在这方面，对这些例程的优化非常有趣。在本文中，我们提出并描述了两种修改。第一的，我们推导出更准确的 QED 事件率的上限估计，并使用它以比以前更有效的方式安排全局时间步的局部子步进。其次，我们提出了一种新的同步加速器功能的高性能实现。我们的优化可以根据问题将计算速度提高 13.7 倍。我们的实现被集成到 PICADOR 和 Hi-Chi 代码中，后者是公开发布的（https://github.com/hi-chi/pyHiChi）。