Extending Polyhedral Techniques towards Parallel Specifications and Approximations

Alexandre Isoard 1, 2
2 COMPSYS - Compilation and embedded computing systems
Inria Grenoble - Rhône-Alpes, LIP - Laboratoire de l'Informatique du Parallélisme
Abstract : Polyhedral techniques enable the application of analysis and code transformations on multi-dimensional structures such as nested loops and arrays. They are usually restricted to sequential programs whose control is both affine and static. This thesis extend them to programs involving for example non-analyzable conditions or expressing parallelism. The first result is the extension of the analysis of live-ranges and memory conflicts, for scalar and arrays, to programs with parallel or approximated specification. In previous work on memory allocation for which this analysis is required, the concept of time provides a total order over the instructions and the existence of this order is an implicit requirement. We showed that it is possible to carry out such analysis on any partial order which match the parallelism of the studied program. The second result is to extend memory folding techniques, based on Euclidean lattices, to automatically find an appropriate basis from the set of memory conflicts. This set is often non convex, case that was inadequately handled by the previous methods. The last result applies both previous analyzes to "pipelined" blocking methods, especially in case of parametric block size. This situation gives rise to non-affine control but can be processed accurately by the choice of suitable approximations. This paves the way for efficient kernel offloading to accelerators such as GPUs, FPGAs or other dedicated circuit.
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Submitted on : Tuesday, September 20, 2016 - 2:00:17 PM
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Alexandre Isoard. Extending Polyhedral Techniques towards Parallel Specifications and Approximations. Other [cs.OH]. Université de Lyon, 2016. English. ⟨NNT : 2016LYSEN011⟩. ⟨tel-01369014⟩

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