arXiv subjects

Sven O. Krumke

Publications and source records attributed to Sven O. Krumke.

21 records · Page 2Linked to original sources

arXiv2016

On the Complexity and Approximability of Budget-Constrained Minimum Cost Flows

We investigate the complexity and approximability of the budget-constrained minimum cost flow problem, which is an extension of the traditional minimum cost flow problem by a second kind of costs associated with each edge, whose total value in a feasible flow is constrained by a given budget B. This problem can, e.g., be seen as the application of the ε-constraint method to the bicriteria minimum cost flow problem. We show that we can solve the problem exactly in weakly polynomial time $O(\log M \cdot MCF(m,n,C,U))$, where C, U, and M are upper bounds on the largest absolute cost, largest capacity, and largest absolute value of any number occuring in the input, respectively, and MCF(m,n,C,U) denotes the complexity of finding a traditional minimum cost flow. Moreover, we present two fully polynomial-time approximation schemes for the problem on general graphs and one with an improved running-time for the problem on acyclic graphs.

cs.DS↗

arXiv2015

ReOpt: an Algorithm with a Quality Guaranty for Solving the Static Relocation Problem

In a carsharing system, a fleet of cars is distributed at stations in an urban area, customers can take and return cars at any time and station. For operating such a system in a satisfactory way, the stations have to keep a good ratio between the numbers of free places and cars in each station. This leads to the problem of relocating cars between stations, which can be modeled within the framework of a metric task system. In this paper, we focus on the Static Relocation Problem, where the system has to be set into a certain state, outgoing from the current state. We present a combinatorial approach and provide approximation factors for several different situations.

cs.DS↗

arXiv2009

Complexity of Strong Implementability

We consider the question of implementability of a social choice function in a classical setting where the preferences of finitely many selfish individuals with private information have to be aggregated towards a social choice. This is one of the central questions in mechanism design. If the concept of weak implementation is considered, the Revelation Principle states that one can restrict attention to truthful implementations and direct revelation mechanisms, which implies that implementability of a social choice function is easy to check. For the concept of strong implementation, however, the Revelation Principle becomes invalid, and the complexity of deciding whether a given social choice function is strongly implementable has been open so far. In this paper, we show by using methods from polyhedral theory that strong implementability of a social choice function can be decided in polynomial space and that each of the payments needed for strong implementation can always be chosen to be of polynomial encoding length. Moreover, we show that strong implementability of a social choice function involving only a single selfish individual can be decided in polynomial time via linear programming.

cs.CC↗