一个平行引力N体核
A parallel gravitational N-body kernel
摘要：
我们描述了{ \tt kira}直接引力$N$ -体积分器的源代码级并行化，它是{ \tt starlab}生产环境中用于模拟致密恒星系统的主力。并行化策略，称为“j-并行化”，涉及通过将系统中的所有粒子分布在可用处理器之间来划分计算域。粒子上的部分力由它们的父处理器并行计算，然后在最终的全局操作中求和。一旦获得总的力，计算元件就继续计算它们的粒子轨迹。我们报告的时间测量的结果在四个不同的并行计算机，并比较它们与理论预测。计算机采用高速互连、NUMA架构以最小化通信开销，或者分布在网格中。代码在测试的域中扩展良好，范围从1024 - 65536星，1 - 128处理器，提供令人满意的加速比。对于分布在三个站点上的60多个处理器来说，在网格上运行生产环境变得低效。
英文摘要：
We describe source code level parallelization for the {\tt kira} direct gravitational $N$-body integrator, the workhorse of the {\tt starlab} production environment for simulating dense stellar systems. The parallelization strategy, called ``j-parallelization'', involves the partition of the computational domain by distributing all particles in the system among the available processors. Partial forces on the particles to be advanced are calculated in parallel by their parent processors, and are then summed in a final global operation. Once total forces are obtained, the computing elements proceed to the computation of their particle trajectories. We report the results of timing measurements on four different parallel computers, and compare them with theoretical predictions. The computers employ either a high-speed interconnect, a NUMA architecture to minimize the communication overhead or are distributed in a grid. The code scales well in the domain tested, which ranges from 1024 - 65536 stars on 1 - 128 processors, providing satisfactory speedup. Running the production environment on a grid becomes inefficient for more than 60 processors distributed across three sites.
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