周期边界解自适应有限差分格式的快速实现与重新优化

Fast Implementation and Re-Optimization for Solution-Adaptive Finite Difference Schemes under Periodic Boundary Conditions

  • 摘要: 经典有限差分格式在中高波数范围内存在显著色散误差。DRP(色散关系保持)格式在波数空间优化相位误差以改善色散特性。解自适应有限差分格式的模板系数随数值解重新优化,以适应不同数值解的谱分布。然而,频繁重新优化带来额外计算开销,且缺少重新优化间隔的确定准则。本文利用周期边界下差分算子的循环矩阵性质,降低优化所需统计量的计算量;进而构造基于一阶导数截断误差预测与FLOPs(浮点运算次数)的重新优化策略,给出该模型下的最优间隔。FLOPs可预先估计,并通过实际运行时间验证其作为成本指标的合理性。以七点中心差分格式为例,三个周期非线性算例表明,本文方法以较小附加计算代价显著降低误差。

     

    Abstract: Classical finite difference schemes exhibit significant dispersion errors at medium-to-high wavenumbers. DRP (dispersion-relation-preserving) schemes mitigate these errors by optimizing phase accuracy in wavenumber space, while solution-adaptive schemes re-optimize stencil coefficients according to the evolving solution spectrum. However, frequent re-optimization incurs additional computational cost, and no criterion exists for selecting the interval. By exploiting the circulant structure of difference operators under periodic boundary conditions, this study reduces the cost of computing the statistics needed for optimization. A re-optimization strategy combining first-derivative truncation-error prediction with floating-point operation counts (FLOPs) is developed to determine the optimal interval for the proposed model. FLOPs can be estimated a priori, and their suitability as a cost metric is validated against measured runtime. Numerical results using a seven-point central difference scheme on three periodic nonlinear problems show that the proposed method significantly reduces errors at low additional computational cost.

     

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