LULESH

"The Shock Hydrodynamics Challenge Problem was originally defined and implemented by LLNL as one of five challenge problems in the DARPA UHPC program and has since become a widely studied proxy application in DOE co-design efforts for exascale. It has been ported to a number of programming models and optimized for a number of advanced platforms – many of those versions are available in the downloads section below. This page gives a brief description of why the problem was chosen. LULESH Ports details other versions and performance tuning work done on the initial version of LULESH, while LULESH 2.0 Changes details the changes made from LULESH 1.0 to LULESH 2.0. A presentation describing the OpenACC port is found here.

Computer simulations of a wide variety of science and engineering problems require modeling hydrodynamics, which describes the motion of materials relative to each other when subject to forces. Many important simulation problems of interest to DOE involve complex multi-material systems that undergo large deformations. LULESH is a highly simplified application, hard-coded to only solve a simple Sedov blast problem with analytic answers – but represents the numerical algorithms, data motion, and programming style typical in scientific C or C++ based applications.

LULESH represents a typical hydrocode, like ALE3D. LULESH approximates the hydrodynamics equations discretely by partitioning the spatial problem domain into a collection of volumetric elements defined by a mesh. A node on the mesh is a point where mesh lines intersect. LULESH is built on the concept of an unstructured hex mesh. Instead, indirection arrays that define mesh relationships are used. The default test case for LULESH appears to be a regular cartesian mesh, but this is for simplicity only – it is important to retain the unstructured data structures as they are representative of what a more complex geometry will require. When modifying LULESH it is important to not take advantage of this or other simplifications in the application. We have tried to spell these out in this technical report, but the list may not be complete."

https://codesign.llnl.gov/lulesh.php

https://www.nextplatform.com/2017/03/15/arm-antes-hpc-software-stack/