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arXiv · 1104.2799

Using Hashing to Solve the Dictionary Problem (In External Memory)

John Iacono·Mihai Pǎtraşcu
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Abstract

We consider the dictionary problem in external memory and improve the update time of the well-known buffer tree by roughly a logarithmic factor. For any \lambda >= max {lg lg n, log_{M/B} (n/B)}, we can support updates in time O(\lambda / B) and queries in sublogarithmic time, O(log_\lambda n). We also present a lower bound in the cell-probe model showing that our data structure is optimal. In the RAM, hash tables have been used to solve the dictionary problem faster than binary search for more than half a century. By contrast, our data structure is the first to beat the comparison barrier in external memory. Ours is also the first data structure to depart convincingly from the indivisibility paradigm.

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John Iacono, Mihai Pǎtraşcu. 2011-04-14. Using Hashing to Solve the Dictionary Problem (In External Memory). https://arxiv.org/abs/1104.2799

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