Bee+Cl@k: An Implementation of Lattice-Based Array Contraction in the Source-to-Source Translator ROSE
Résumé
We build on prior work on intra-array memory reuse, for which a general theoretical framework was proposed based on lattice theory. Intra-array memory reuse is a way of reducing the size of a temporary array by folding, thanks to affine mappings and modulo operations, reusing memory locations when they contain a value not used later. We describe the algorithms needed to implement such a strategy. Our implementation has two parts. The first part, Bee, uses the source-to-source transformer ROSE to extract from the program all necessary information on the lifetime of array elements and to generate the code after memory reduction. The second part, Cl@k, is a stand-alone mathematical tool dedicated to optimizations on polyhedra, in particular the computation of successive minima and the computation of good admissible lattices, which are the basis for lattice-based memory reuse. Both tools are developed in C++ and use linear programming and polyhedra manipulations. They can be used either for embedded program optimizations, e.g., to limit memory expansion introduced for parallelization, or in high-level synthesis, e.g., to design memories between communicating hardware accelerators.
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