CppCon 2024

C++ 20 developers do not need to sacrifice high-level expressiveness and code cleanliness for high performance when writing cross-platform code. Concepts and constraints combined with build tool configuration and judicious use of the preprocessor can enable novel techniques resulting in significant improvements to cross-platform architectures. The techniques are the result of experiences in the video games and embedded software fields; however, the techniques are applicable to high performance scientific code and general applications supporting multiple platforms

This presentation discusses how various features of C++ may be used to develop high-level and high-performance code in cross-platform projects. It focuses on the design and implementation of a small family of quaternion classes. Quaternions are a small numeric type used extensively in 3D graphics and thus ideal as the focus. The discussion begins with an unoptimized implementation that will compile on all platforms. Optimized versions for multiple architectures (SSE/AVX, Neon, and WebAssembly SIMD) will be added. These optimized types are added without changing a single line of existing code. Additionally, supporting multiple revisions of a spec will be illustrated. Implementing new revisions does not result in changing any pre-existing files, and new revisions may leverage older revisions and need not ever reimplement pre-existing functions. This reduces code repetition and all its attendant liabilities.