论文标题

与混乱的动力学系统及时平行

Toward Parallel in Time for Chaotic Dynamical Systems

论文作者

Vargas, David A., Falgout, Robert D., Günther, Stefanie, Schroder, Jacob B.

论文摘要

随着CPU时钟速度停滞不前,高性能计算机继续具有更高的核心计数,需要增加并行性来利用这些新的体系结构。传统的串行时间构造方案是一个重要的瓶颈,因为许多类型的模拟需要大量的时间步长,必须依次计算出来。时间方案(例如,时间(MGRIT)方法的多机减少)并行,通过在时间步长跨时步中并行解决此问题,并在抛物线问题上显示出令人鼓舞的结果。但是,由于混乱的初始价值问题本质上是错误的条件,因此混乱的问题已被证明更加困难。 mgrit依赖于连续更粗的时间网格的层次结构,以迭代地校正最好的时机上的解决方案,但是由于混乱系统的性质,在较粗糙的水平上微妙的不准确性可能会导致较差的粗网格校正。在这里,我们提出了对非线性FAS Multigrid的修改,以及一种新颖的时期方案,该方案可以更好地捕获粗网格上的长期行为,并大大提高了混乱的初始价值问题的MGRIT收敛性。我们为Lorenz系统模型问题提供了支持的数值结果。

As CPU clock speeds have stagnated, and high performance computers continue to have ever higher core counts, increased parallelism is needed to take advantage of these new architectures. Traditional serial time-marching schemes are a significant bottleneck, as many types of simulations require large numbers of time-steps which must be computed sequentially. Parallel in Time schemes, such as the Multigrid Reduction in Time (MGRIT) method, remedy this by parallelizing across time-steps, and have shown promising results for parabolic problems. However, chaotic problems have proved more difficult, since chaotic initial value problems are inherently ill-conditioned. MGRIT relies on a hierarchy of successively coarser time-grids to iteratively correct the solution on the finest time-grid, but due to the nature of chaotic systems, subtle inaccuracies on the coarser levels can lead to poor coarse-grid corrections. Here we propose a modification to nonlinear FAS multigrid, as well as a novel time-coarsening scheme, which together better capture long term behavior on coarse grids and greatly improve convergence of MGRIT for chaotic initial value problems. We provide supporting numerical results for the Lorenz system model problem.

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