UBC Theses and Dissertations

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UBC Theses and Dissertations

Scalable and deterministic timing-driven parallel placement for FPGAs Wang, Chao Chris


This thesis describes a parallel implementation of the timing-driven VPR 5.0 simulated-annealing placement engine. By partitioning the grid into regions and allowing distant data to grow stale, it is possible to consider a large number of non-conflicting moves in parallel and achieve a deterministic result. The full timing-driven placement algorithm is parallelized, including swap evaluation, bounding-box calculation and the detailed timing-analysis updates. The partitioned region approach slightly degrades the placement quality, but this is necessary to expose greater parallelism. We also suggest a method to recover the lost quality. In simulated annealing, runtime can be shortened at the expense of quality. Using this method, the serial placer can achieve a maximum speedup of 100X while quality metrics degrades as much as 100%. In contrast, the parallel placer can scale beyond 500X with all quality metrics degrading by less than 30%. Specifically, at the point where the parallel placer begins to dominate over the serial placer, the post-routing minimum channel width, wirelength and critical-path delay degrades 13%, 10% and 7% respectively on average compared to VPR’s original algorithm,while achieving a 140X to 200X speedup 25 threads. Finally, it is shown that the amount of degradation in the parallel placer is independent of the number of threads used.

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