On Lookahead in the List Update Problem

Simha, R. and A. Majumdar, On Lookahead in the List Update Problem. Information Processing Letters. We study a problem in the area of self-adjusting data structures: algorithms for the singly-linked list for the case in which a sequence of operations is to be performed on the list and the entire sequence is known beforehand. Whereas past approaches assume that the cost of lookahead is zero, we explicitly take into account this cost and allow for diierent list access and lookahead costs, parametrically speciied by a ratio. Our main result is that the well-known Move-to-Front algorithm is 2-competitive with an algorithm that scans the entire sequence of operations. Simulation results point to a remarkably counter-intuitive observation: the optimal strategy is to either scan the entire sequence of operations or not scan it at all.