Parallel merging: algorithm and implementation results

An efficient parallel algorithm for merging two sorted lists is presented. The algorithm is based on a novel partitioning algorithm that splits the two lists among the processors, in a way that ensures load balance during the merge. The partitioning algorithm can itself be efficiently parallelized, allowing the solution to scale with increased numbers of processors. A shared memory multiprocessor is assumed. The time complexity for partitioning and merging is O(N/p + log N), where p is the number of processors and N is the total number of elements in the two lists. Implementation results on a twenty node Sequent Symmetry multiprocessor are also presented. © 1990.