On Approximating Optimal Weighted Lobbying, and Frequency of Correctness Versus Average-Case Polynomial Time

We investigate issues regarding two hard problems related to voting, the optimal weighted lobbying problem and the winner problem for Dodgson elections. Regarding the former, Christian et al. [2] showed that optimal lobbying is intractable in the sense of parameterized complexity. We provide an efficient greedy algorithm that achieves a logarithmic approximation ratio for this problem and even for a more general variant--optimal weighted lobbying. We prove that essentially no better approximation ratio than ours can be proven for this greedy algorithm. The problem of determining Dodgson winners is known to be complete for parallel access to NP [11]. Homan and Hemaspaandra [10] proposed an efficient greedy heuristic for finding Dodgson winners with a guaranteed frequency of success, and their heuristic is a "frequently selfknowingly correct algorithm." We prove that every distributional problem solvable in polynomial time on the average with respect to the uniform distribution...

• Type: Conference
• Year: 2007
• Where: FCT
• Authors: Gábor Erdélyi, Lane A. Hemaspaandra, Jörg Rothe, Holger Spakowski
• Keywords: Applied Computing, FCT 2007, Greedy Algorithm, Weighted Lobbying, Weighted Lobbying Problem