Scheduling seminar

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schedulingseminar@rtime.felk.cvut.cz

December 2021

1 participants
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Rubén Ruiz (UP de València)| December 22| State-of-the-art flowshop scheduling heuristics: Dos and Don'ts
by Zdeněk Hanzálek 20 Dec '21

20 Dec '21

Dear scheduling researcher, We are delighted to announce the talk given by Rubén Ruiz (UP de València). The title is "State-of-the-art flowshop scheduling heuristics: Dos and Don'ts". The seminar will take place on Zoom on Wednesday, December 22 at 14:00 UTC. Join Zoom Meeting https://cesnet.zoom.us/j/91381308994?pwd=bFgzTFR1ZzlNNHpybTc5YTlTTHRxQT09 Meeting ID: 913 8130 8994 Passcode: 212305 You can follow the seminar online or offline on our Youtube channel as well: https://www.youtube.com/channel/UCUoCNnaAfw5NAntItILFn4A The abstract follows. Many scheduling problems are simply too hard to be solved exactly, especially for instances of medium or large size or when realistic constraints are present. As a result, the literature on heuristics and metaheuristics for scheduling is extensive. More often than not, metaheuristics are capable of generating solutions close to optimality or to tight lower bounds for instances of realistic size in a matter of minutes. Metaheuristics have been refined over the years and there are literally hundreds of papers published every year with applications to most domains in many different journals. Most regrettably, some of these methods are complex in the sense that they have many parameters that affect performance and hence need careful calibration. Furthermore, many times published results are hard to reproduce due to specific speed-ups being used or complicated software constructs. These complex methods are difficult to transfer to industries in the case of scheduling problems. Another important concern is the recently recognized “tsunami” of novel metaheuristics that mimic the most bizarre natural or human processes, as for example intelligent water drops, harmony search, firefly algorithms and the like. See K. Sörensen “Metaheuristics—The Metaphor exposed” (2015), ITOR 22(1):3-18. In this presentation, we briefly review different flowshop problems and variants. From the basic flowshop problem with makespan minimization to other objectives like flowtime minimization, flowshops with sequence-dependent setup times, no-idle flowshops, all the way up to complex hybrid flexible flowline problems. We will show how simple Iterated Greedy (IG) algorithms often outperform much more complex approaches. IG methods are inherently simple with very few parameters. They are easy to code and results are easy to reproduce. We will show that for all tested problems so far they show state-of-the-art performance despite their simplicity. As a result, we will defend the choice of simpler, yet good performing approaches over complicated metaphor-based algorithms. The next talk in our series will be given by Christian Artigues (LAAS-CNRS Toulouse)| December 22| For more details, please visit https://schedulingseminar.com/ With kind regards Zdenek, Mike and Guohua -- Zdenek Hanzalek Industrial Informatics Department, Czech Institute of Informatics, Robotics and Cybernetics, Czech Technical University in Prague, Jugoslavskych partyzanu 1580/3, 160 00 Prague 6, Czech Republic https://rtime.ciirc.cvut.cz/~hanzalek/

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Christoph Dürr (Sorbonne Uni)| December 8 | Three models for scheduling under explorable uncertainty
by Zdeněk Hanzálek 06 Dec '21

06 Dec '21

Dear scheduling researcher, We are delighted to announce the talk given by Christoph Dürr <http://www.lip6.fr/Christoph.Durr> (Sorbonne Uni). The title is "Three models for scheduling under explorable uncertainty". The seminar will take place on Zoom on Wednesday, December 8 at 14:00 UTC. Join Zoom Meeting https://cesnet.zoom.us/j/94434410356?pwd=SWlmUElObjhtQWZCcm9PZGw5TTVnZz09 <https://cesnet.zoom.us/j/94434410356?pwd=SWlmUElObjhtQWZCcm9PZGw5TTVnZz09> Meeting ID: 944 3441 0356 Passcode: 040955 You can follow the seminar online or offline on our Youtube channel as well: https://www.youtube.com/channel/UCUoCNnaAfw5NAntItILFn4A The abstract follows. We consider a single machine scheduling problem, where every job has a processing time and a priority weight and the objective is to minimize the total weighted sum of completion times. The novelty is that the job characteristics are initially given in an imprecise manner to the algorithm. Tests can be performed for chosen jobs to learn their precise values, allowing for a better ordering of the jobs in the schedule. These tests however take some time, delaying the subsequent schedule. The algorithm needs to produce a schedule consisting of executions of all jobs and tests of some jobs. We will present three different models that have been studied in this context, as well as the results obtained for each of them. The talk covers papers authored by Levi, Magnanti and Shaposhnik, by C.D., Thomas Erlebach, Nicole Megow, Julie Meißner, and by Fanny Dufossé, C.D., Noël Nadal, Denis Trystram and Óscar C. Vásquez. The next talk in our series will be given by Rubén Ruiz (UP de València)| December 22| State-of-the-art flowshop scheduling heuristics: Dos and Don'ts For more details, please visit https://schedulingseminar.com/ With kind regards Zdenek, Mike and Guohua -- Zdenek Hanzalek Industrial Informatics Department, Czech Institute of Informatics, Robotics and Cybernetics, Czech Technical University in Prague, Jugoslavskych partyzanu 1580/3, 160 00 Prague 6, Czech Republic https://rtime.ciirc.cvut.cz/~hanzalek/

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