Compiler support for semi-manual AoS-to-SoA conversions with data views

TL;DR

This paper introduces a C++ language extension with compiler support for semi-manual AoS-to-SoA conversions using data views, enabling flexible data layout experimentation in high-performance computing applications.

Contribution

It proposes a novel language extension with annotations for guiding automatic data layout conversions in C++, implemented in Clang.

Findings

Enables easy experimentation with data layouts in C++ code.

Automates data conversions based on developer annotations.

Demonstrates effectiveness in a smoothed particle hydrodynamics application.

Abstract

The C programming language and its cousins such as C++ stipulate the static storage of sets of structured data: Developers have to commit to one, invariant data model -- typically a structure-of-arrays (SoA) or an array-of-structs (AoS) -- unless they manually rearrange, i.e.~convert it throughout the computation. Whether AoS or SoA is favourable depends on the execution context and algorithm step. We propose a language extension based upon C++ attributes through which developers can guide the compiler what memory arrangements are to be used. The compiler can then automatically convert (parts of) the data into the format of choice prior to a calculation and convert results back afterwards. As all conversions are merely annotations, it is straightforward for the developer to experiment with different storage formats and to pick subsets of data that are subject to memory rearrangements. Our work implements the annotations within Clang and demonstrates their potential impact through a smoothed particle hydrodynamics (SPH) code.