A combined BIT and TIMESTAMP algorithm for the list update problem

Abstract. A simple randomized on-line algorithm for the list update problem is presented that achieves a competitive factor of 1.6, the best known so far. The algorithm makes an initial random choice between two known algorithms that have dierent worst-case request sequences. The rst is the BIT algorithm that, for each item in the list, alternates between moving it to the front of the list and leaving it at its place after it has been requested. The second is a TIMESTAMP algorithm that moves an item in front of less often requested items within the list