Concurrent AVL Revisited: Self-Balancing Distributed Search Trees
Abstract
We address the concurrent insertion and deletion of keys in binary almost balanced search trees (AVL trees). We show that this problem can be studied through the self-reorganization of distributed systems of processes controlled by local evolution rules in the line of the approach of Dijkstra and Scholten. This yields a simple and abstract presentation of the insertion and deletion mechanisms. In particular, we show that our approach encapsulates a number of previous attempts described in the literature. They can in fact be seen as ad hoc specializations of the nondeterministic evolution rules. This solves in a very general setting an old question raised by H.T. Kung and P.L. Lehman: where should rotations take place to rebalance arbitrary trees?
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