One-Pass Algorithm

Synonyms

Data stream algorithm; One-pass algorithm; Streaming algorithm

Definition

A one-pass algorithm receives as input a list of data items x₁, x₂, x₃,…. It can read these data items only once, from left to right, i.e., in increasing order of the indices i = 1, 2, 3,…. Critical parameters of a one-pass algorithm are (1) the size of the memory used by the algorithm, and (2) the processing time per data item x_i. Typically, a one-pass algorithm is designed for answering one particular query against the input data. To this end, the algorithm stores and maintains a suitable data structure which, for each i, is updated when reading data item x_i.

The two parameters processing time per data item and memory size are usually measured as functions depending on the size N of the input (different measures of the input sizeare considered in the literature, among them, e.g., the number of data items occurring in the input, as well as the total number of bits needed for storing the entire input)....