A high-performance implementation of a multiphase lattice Boltzmann method based on the conservative Allen-Cahn model supporting high-density ratios and high Reynolds numbers is presented. Meta-programming techniques are used to generate optimized code for CPUs and GPUs automatically. The coupled model is specified in a high-level symbolic description and optimized through automatic transformations. The memory footprint of the resulting algorithm is reduced through the fusion of compute kernels. A roofline analysis demonstrates the excellent efficiency of the generated code on a single GPU. The resulting single GPU code has been integrated into the multiphysics framework waLBerla to run massively parallel simulations on large domains. Communication hiding and GPUDirect-enabled MPI yield near-perfect scaling behavior. Scaling experiments are conducted on the Piz Daint supercomputer with up to 2048 GPUs, simulating several hundred fully resolved bubbles. Further, validation of the implementation is shown in a physically relevant scenario—a three-dimensional rising air bubble in water.

提出了一种基于保守Allen-Cahn模型的多相晶格Boltzmann方法的高性能实现，该模型支持高密度比和高雷诺数。元编程技术用于自动为CPU和GPU生成优化的代码。耦合模型在高级符号描述中指定，并通过自动转换进行了优化。通过融合计算内核，减少了所得算法的内存占用量。屋顶分析显示了在单个GPU上生成代码的出色效率。生成的单个GPU代码已集成到多物理场框架waLBerla中，以在大域上运行大规模并行仿真。通信隐藏和启用GPUDirect的MPI产生了近乎完美的缩放行为。在具有多达2048个GPU的Piz Daint超级计算机上进行缩放实验，模拟了数百个完全分解的气泡。此外，在物理上相关的场景中显示了实现的验证-水中的三维上升气泡。