Merge Sort - Parallel Processing

Parallel Processing

Merge sort parallelizes well due to use of the divide-and-conquer method. A parallel implementation is shown in pseudo-code in the third edition of Cormen, Leiserson, and Stein's Introduction to Algorithms. This algorithm uses a parallel merge algorithm to not only parallelize the recursive division of the array, but also the merge operation. It performs well in practice when combined with a fast stable sequential sort, such as insertion sort, and a fast sequential merge as a base case for merging small arrays. Merge sort was one of the first sorting algorithms where optimal speed up was achieved, with Richard Cole using a clever subsampling algorithm to ensure O(1) merge. Other sophisticated parallel sorting algorithms can achieve the same or better time bounds with a lower constant. For example, in 1991 David Powers described a parallelized quicksort (and a related radix sort) that can operate in O(log n) time on a CRCW PRAM with n processors by performing partitioning implicitly.

Read more about this topic:  Merge Sort

Famous quotes containing the word parallel:

    As I look at the human story I see two stories. They run parallel and never meet. One is of people who live, as they can or must, the events that arrive; the other is of people who live, as they intend, the events they create.
    Margaret Anderson (1886–1973)