Efficient Tree Layout in a Multilevel Memory Hierarchy
<|reference_start|>Efficient Tree Layout in a Multilevel Memory Hierarchy: We consider the problem of laying out a tree with fixed parent/child structure in hierarchical memory. The goal is to minimize the expected number of block transfers performed during a search along a root-to-leaf path, subject to a given probability distribution on the leaves. This problem was previously considered by Gil and Itai, who developed optimal but slow algorithms when the block-transfer size B is known. We present faster but approximate algorithms for the same problem; the fastest such algorithm runs in linear time and produces a solution that is within an additive constant of optimal.   In addition, we show how to extend any approximately optimal algorithm to the cache-oblivious setting in which the block-transfer size is unknown to the algorithm. The query performance of the cache-oblivious layout is within a constant factor of the query performance of the optimal known-block-size layout. Computing the cache-oblivious layout requires only logarithmically many calls to the layout algorithm for known block size; in particular, the cache-oblivious layout can be computed in O(N lg N) time, where N is the number of nodes.   Finally, we analyze two greedy strategies, and show that they have a performance ratio between Omega(lg B / lg lg B) and O(lg B) when compared to the optimal layout.<|reference_end|>
@article{alstrup2002efficient,
    title={Efficient Tree Layout in a Multilevel Memory Hierarchy},
    author={Stephen Alstrup, Michael A. Bender, Erik D. Demaine, Martin
  Farach-Colton, Theis Rauhe, Mikkel Thorup},
    journal={arXiv preprint arXiv:cs/0211010},
    year={2002},
    archivePrefix={arXiv},
    eprint={cs/0211010},
    primaryClass={cs.DS}
}