Improving Reliability of Supercomputer CFD Codes on Unstructured Meshes

The paper describes a particular technical solution targeted at improving reliability and quality of a highly-parallel computational fluid dynamics code written in C++. The code considered is based on rather complex high-accuracy numerical methods and models for simulation of turbulent flows on unstructured hybrid meshes. The cost of software errors is very high in largescale supercomputer simulations. Reproducing and localizing errors, especially “magic” unstable bugs related with wrong memory access, are extremely problematic due to the large amount of computing resources involved. In order to prevent, or at least notably filter out memory bugs, an approach of increased reliability is proposed for representing mesh data and organizing memory access. A set of containers is proposed, which causes no overhead in the release configuration compared to plain arrays. At the same time, it provides throughout access control in the safe mode configuration and additional compile-time protection from programming errors. Furthermore, it is fully compatible with heterogeneous computing within the OpenCL standard. The proposed approach provides internal debugging capabilities that allow us to localize problems directly in a supercomputer simulation.