Abstract. This paper deals with the design of improved construction heuristics and iterated local search for the Routing and Wavelength Assignment problem (RWA). Given a physical network and a set of communication requests, the static RWA deals with the problem of assigning suitable paths and wavelengths to the requests. We introduce benchmark instances from the SND library to the RWA and argue that these instances are more challenging than previously used random instances. We analyze the properties of several instances in detail and propose an improved construction heuristic to handle 'problematic' instances. Our iterated local search finds the optimum for most instances.
The Routing and Wavelength Assignment problem is a graph optimization problem which deals with optical networks, where communication requests in a network have to be fulfilled. In this paper, we present a multilevel distributed memetic algorithm (ML-DMA) for the static RWA which finds provable optimal solutions for most benchmark instances with known lower bounds and is capable of handling large instances. Components of our ML-DMA include iterated local search, recombination, multilevel scaling, and a gossip-based distribution algorithm. Results demonstrated that our ML-DMA is among the most sophisticated heuristic RWA algorithms published so far.
One major problem for the design of cyber-physical systems is the understanding of problems that can arise from the interaction of discrete and continuous behaviors, i.e., the behaviors of hybrid systems whose discrete states enable attached differential equations. Tools like Simulink, Labview, Scicos, and Dymola are powerful choices for the simulation of such systems. However, the modeling capabilities of these tools are limited to a composition of given blackbox modules, so that they miss the notion of typical programs. To make use of algorithmic models, we recently proposed an extension of the synchronous programming language Quartz to model, simulate, and verify cyber-physical systems. We developed an operational semantics of this language that formally specifies a simulator, and we also defined a translation to hybrid state transition systems for the formal verification of these systems.In this paper, we describe how our Quartz language and the related Averest toolset can be used for teaching cyberphysical systems. We present the concept of an introductory course for modeling, simulation, and verification of these systems in a Master program in Computer Science. The goal of the lecture is to provide a broad overview to introduce the students to the main research areas in this field. Besides a theoretical foundation, we emphasize the combination of lecture courses with practical exercises using our Averest tools for simulation and verification. This way, we show our students several effects that may occur in the design of cyber-physical systems like zeno behaviors, urgent transitions, real-time requirements, etc.
In this paper we present a multilevel approach for the static Routing and Wavelength Assignment (RWA) problem. The RWA deals with the problem of assigning paths and wavelengths to requests in optical communication networks. The multilevel approach is a general solution strategy involving stepwise coarsening the original problem instance, solving a simplified instance and expanding the solution back to the original size.We propose both a multilevel-inspired construction heuristic and a multilevel algorithm using iterated local search for refinement. These algorithms significantly improve previous approaches regarding time consumption and solution quality for large instances.
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