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T.B. Klos

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7 records found

Conference paper (2017) - Kiriakos Simon Mountakis, Tomas Klos, Cees Witteveen
This paper concerns networks of precedence constraints between tasks with random durations, known as stochastic task networks, often used to model uncertainty in real-world applications. In some applications, we must associate tasks with reliable start-times from which realized start-times will (most likely) not deviate too far. We examine a dispatching strategy according to which a task starts as early as precedence constraints allow, but not earlier than its corresponding planned release-time. As these release-times are spread farther apart on the time-axis, the randomness of realized start-times diminishes (i.e. stability increases). Effectively, task start-times becomes less sensitive to the outcome durations of their network predecessors. With increasing stability, however, performance deteriorates (e.g. expected makespan increases). Assuming a sample of the durations is given, we define an LP for finding release-times that minimize the performance penalty of reaching a desired level of stability. The resulting LP is costly to solve, so, targeting a specific part of the solution-space, we define an associated Simple Temporal Problem (STP) and show how optimal release-times can be constructed from its earliest-start-time solution. Exploiting the special structure of this STP, we present our main result, a dynamic programming algorithm that finds optimal release-times with considerable efficiency gains. ...
Conference paper (2015) - Simon Mountakis, Tomas Klos, Cees Witteveen
We discuss two flexibility metrics for Simple Temporal Networks (STNs): the so-called naive flexibility metric based on the difference between earliest and latest starting times of temporal variables, and a recently proposed concurrent flexibility metric. We establish an interesting connection between the computation of these flexibility metrics and properties of the minimal distance matrix DS of an STN S: the concurrent flexibility metric can be computed by finding a minimum weight matching of a weighted bipartite graph completely specified by DS, while the naive flexibility metric corresponds to computing a maximum weight matching in the same graph. From a practical point of view this correspondence offers an advantage: instead of using an O(n5) LP-based approach, reducing the problem to a matching problem we derive an O(n3) algorithm for computing the concurrent flexibility metric. ...
Conference paper (2010) - TB Klos, G.J. van Ahee, K. Tuyls
Conference paper (2007) - P. van Maanen, TB Klos, K. van Dongen
Journal article (2006) - Han Noot, Koye Somefun, Tomas B. Klos, Valentin Robu, Han La Poutré
We present a visualization of bargaining processes between a seller and a buyer (or buyers) where negotiations take place over the composition and price of bundles of goods. The negotiations themselves are simulated by software specific for the kind of negotiations. The visualization collects information from the simulation steps in a simulation-specific way and visualizes those steps in a general way. We demonstrate the visualization for two cases: a seller who offers bundles of linearly dependent items to many customers and a seller who repeatedly offers a bundle of non linearly dependent goods to a specific customer meanwhile learning this customers preferences. ...