Best Increments for the Average Case of Shellsort

This paper presents the results of using sequential analysis to find increment sequences that minimize the average running time of Shellsort, for array sizes up to several thousand elements. The obtained sequences outperform by about 3% the best ones known so far, and there is a plausible evidence that they are the optimal ones. 1 Shellsort A well implemented Shellsort is among the fastest general algorithms for sorting arrays of several dozen elements, and even for huge arrays it is not prohibitively slow. Moreover, it is an adaptive method that runs faster on “nearly sorted” arrays that often occur in practice. Published by D. L. Shell in 1959 [11], it is one of the earliest sorts discovered, it can be easily understood and implemented, yet its analysis is difficult and still incomplete. Shellsort for N elements X[0, . . . , N−1] is based on a predetermined sequence

• Type: Conference
• Year: 2001
• Where: FCT
• Authors: Marcin Ciura
• Keywords: Applied Computing, Average Running Time, Fastest General Algorithms, FCT 2001, Increment Sequences