String matching and indexing with suffix data structures

Ph.DDOCTOR OF PHILOSOPH

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 algorithms when the block-transfer size is known. 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 with known block size. Finally, we analyze two greedy strategies, and show that they have a performance ratio between Ω(lg B/lg lg B) and O(lg B) when compared to the optimal layout.

Efficient Tree Layout in a Multilevel Memory Hierarchy

We consider the problem of laying out a tree or trie in a hierarchical memory, where the tree/trie has a fixed parent/child structure. The goal is to minimize..