Binary Searching with Nonuniform Costs and Its Application to Text Retrieval

We study the problem of minimizing the expected cost of binary searching for data where the access cost is not fixed and depends on the last accessed element, such as data stored in magnetic or optical disk. We present an optimal algorithm for this problem that finds the optimal search strategy in O(n3) time, which is the same time complexity of the simpler classical problem of fixed costs. Next, we present two practical linear expected time algorithms, under the assumption that the access cost of an element is independent of its physical position. Both practical algorithms are online, that is, they find the next element to access as the search proceeds. The first one is an approximate algorithm which minimizes the access cost disregarding the goodness of the problem partitioning. The second one is a heuristic algorithm, whose quality depends on its ability to estimate the final search cost, and therefore it can be tuned by recording statistics of previous runs. We present an applicati...

• Type: Journal
• Year: 2000
• Where: ALGORITHMICA
• Authors: Gonzalo Navarro, Ricardo A. Baeza-Yates, Eduardo F. Barbosa, Nivio Ziviani, Walter Cunto
• Keywords: Algorithm, ALGORITHMICA 2000, Binary Search, Optical Disks