RAPTOR: Practical Numerical Profiling of Scientific Applications

Figure 1: Qualitative visualization of bubble deformation and splitting over time (𝑡) for the Bubble test case at Reynolds number Re = 3500, performed using incompressible multiphase fluid dynamics solvers in Flash-X. The contours depict the zero level of the level-set function, 𝜙 = 0, which defines the air-water interface (𝜙 > 0 in the air phase and 𝜙 < 0 in the water phase). Adaptive mesh refinement (AMR) levels Ω 𝑀 , Ω 𝑀 -1 , and Ω 𝑀 -2 are shown and labeled in the left panel. AMR dynamically refines the mesh near the interface to accurately capture interface dynamics. We use RAPTOR to truncate FP operations in the advection and diffusion modules of the Navier-Stokes solver following two different strategies. In the first strategy (Trunc. Everywhere), truncation is applied throughout the entire mesh. The second strategy selectively applies truncation in each mesh cell using a cut-off at the 𝑀 -𝑙 AMR level (where 𝑙 = 1, 2, . . .). Insets show zoomed-in views of the liquid-gas interface for simulations using 4 bit and 12 bit mantissas, highlighting the effect of reduced precision on the final simulation outcome. Further details in §6.2.