Access-Adaptive Priority Search Tree
Haley Massa, Jeffrey Uhlmann
In this paper we show that the priority search tree of McCreight, which was
originally developed to satisfy a class of spatial search queries on
2-dimensional points, can be adapted to the problem of dynamically maintaining
a set of keys so that the query complexity adapts to the distribution of
queried keys. Presently, the best-known example of such a data structure is the
splay tree, which dynamically reconfigures itself during each query so that
frequently accessed keys move to the top of the tree and thus can be retrieved
with fewer queries than keys that are lower in the tree. However, while the
splay tree is conjectured to offer optimal adaptive amortized query complexity,
it may require O(n) for individual queries. We show that an access-adaptive
priority search tree (AAPST) can provide competitive adaptive query performance
while ensuring O(log n) worst-case query performance, thus potentially making
it more suitable for certain interactive (e.g.,online and real-time)
applications for which the response time must be bounded.