Efficient unbalanced merge-sort

  • Authors:
  • Enrico Nardelli;Guido Proietti

  • Affiliations:
  • Dipartimento di Matematica, Universití di Roma "Tor Vergata", Via della Ricerca Scientifica, 00133 Roma, Italy and Istituto di Analisi dei Sistemi ed Informatica "A. Ruberti", CNR, Viale Manz ...;Istituto di Analisi dei Sistemi ed Informatica "A. Ruberti", CNR, Viale Manzoni 30, 00185 Roma, Italy and Dipartimento di Informatica, Universití dell'Aquila, Via Vetoio, 67010 L'Aquila, Ital ...

  • Venue:
  • Information Sciences: an International Journal
  • Year:
  • 2006

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Abstract

Sorting algorithms based on successive merging of ordered subsequences are widely used, due to their efficiency and to their intrinsically parallelizable structure. Among them, the merge-sort algorithm emerges indisputably as the most prominent method. In this paper we present a variant of merge-sort that proceeds through arbitrary merges between pairs of quasi-ordered subsequences, no matter which their size may be. We provide a detailed analysis, showing that a set of n elements can be sorted by performing at most n@?logn@? key comparisons. Our method has the same optimal asymptotic time and space complexity as compared to previous known unbalanced merge-sort algorithms, but experimental results show that it behaves significantly better in practice.