Assignment problem

About: Assignment problem is a research topic. Over the lifetime, 7588 publications have been published within this topic receiving 172820 citations. The topic is also known as: marriage problem.

Minimal Assignments for Bounded Model Checking

Abstract: A traditional counterexample to a linear-time safety property shows the values of all signals at all times prior to the error. However, some signals may not be critical to causing the failure. A succinct explanation may help human understanding as well as speed up algorithms that have to analyze many such traces. In Bounded Model Checking (BMC), a counterexample is constructed from a satisfying assignment to a Boolean formula, typically in CNF. Modern SAT solvers usually assign values to all variables when the input formula is satisfiable. Deriving minimal satisfying assignments from such complete assignments does not lead to concise explanations of counterexamples because of how CNF formulae are derived from the models. Hence, we formulate the extraction of a succinct counterexample as the problem of finding a minimal assignment that, together with the Boolean formula describing the model, implies an objective. We present a two-stage algorithm for this problem, such that the result of each stage contributes to identify the “interesting” events that cause the failure. We demonstrate the effectiveness of our approach with an example and with experimental results.

On the Combined Distribution-Assignment of Traffic

Abstract: It has been remarked that in the practice of transportation planning the distribution and assignment computations are treated sequentially as independent problems, although ideally they should be solved simultaneously. A case has been made by many practitioners for repeating the distribution and assignment computations in order to obtain more consistent results. The purpose of this paper is to shed some light on the eventual results of sequentially solving the distribution and assignment problem. Our conclusion, based on rigorous arguments, is that such practice does not lead to valid results. Also, we develop an approach to solving the distribution and assignment problem simultaneously and relate it to other methods that were proposed for this problem. A numerical example illustrates the conclusions drawn.

Network performance under system optimal and user equilibrium dynamic assignments: implications for advanced traveler information systems

Abstract: A comparative assessment was undertaken of network cost and performance under time-dependent system optimal (SO) and user equilibrium (UE) assignment patterns, with particular reference to the effectiveness of advanced traveler information systems (ATIS). Both SO and UE solutions were found using a new simulation-based algorithm for the time-dependent assignment problem. Experiments were conducted using a test network with signal-controlled junctions under progressively increasing network loading intensities. A diagnosis of system performance for various intensities of loading was effected using network-level traffic descriptors for both SO and UE assignments. The results affirm the validity of a meaningful demarcation between SO and UE assignments in urban traffic networks and provide useful insights for macroscopic network-level relations among traffic descriptors. These results suggest that ATIS information supply strategies based on SO route guidance could considerably outperform descriptive noncooperative information strategies, especially at moderate to high congestion levels in the network. The results also illustrate the time-dependent nature of the gains achieved by an SO assignment vis-a-vis a UE assignment in a congested traffic network.

Investigation of stochastic network loading procedures

Abstract: The network loading process of stochastic traffic assignment is investigated. A central issue in the assignment problem is the behavioral assumption governing route choice, which concerns the definition of available routes and the choice model. These two problems are addressed and reviewed. Although the multinomial logit model can be implemented efficiently in stochastic network loading algorithms, the model suffers from theoretical drawbacks, some of them arising from the independence of irrelevant alternatives property. As a result, the stochastic loading on routes that share common links is overloaded at the overlapping parts of the routes. Other logit-family models recently have been proposed to overcome some of the theoretical problems while maintaining the convenient analytical structure. Three such models are investigated: the C-logit model, which was specifically defined for route choice; and two general discrete-choice models, the cross-nested logit model and the paired combinatorial logit model....

A modeling framework for the passenger assignment on a transport network with time-tables

Abstract: This paper presents a new graph theoretic framework for the passenger assignment problem that encompasses simultaneously the departure time and the route choice. The implicit FIFO access to transit lines is taken into account by the concept of available capacity. This notion of flow priority has not been considered explicitly in previous models. A traffic equilibrium model is described and a computational procedure based on asymmetric boarding penalty functions is suggested.