文摘
This paper addresses the page migration problem: given online requests from nodes on a network for accessing a page stored in a node, output online migrations of the page. Serving a request costs the distance between the request and the page, and migrating the page costs the migration distance multiplied by the page size D?. The objective is to minimize the total sum of service costs and migration costs. Black and Sleator conjectured that there exists a 3-competitive deterministic algorithm for every graph. Although the conjecture was disproved for the case D=1, whether or not an asymptotically (with respect to D) 3-competitive deterministic algorithm exists for every graph is still open. In fact, we did not know if there exists a 3-competitive deterministic algorithm for an extreme case of three nodes with D?. As the first step toward an asymptotic version of the Black and Sleator conjecture, we present 3- and (3+1/D)-competitive algorithms on three nodes with D=2 and D?, respectively, and a lower bound of 3+Ω(1/D) that is greater than 3 for every D?. In addition to the results on three nodes, we also derive ρ-competitiveness on complete graphs with edge-weights between 1 and 2?/ρ for any ρ?, extending the previous 3-competitive algorithm on uniform networks.