[rules-users] Employee Shift Rostering: algorithm details

Hi, I'm new both to Drools Planner and to metaheuristic algorithms like Tabu Search. Though I have done some preliminary reading on the Net on how this algorithm 'generally' works -- including reading the 'plain-English' portions of Chapter 8 of the 'Essentials of Metaheuristics' book -- it still isn't perfectly clear to me how an actual implementation of the algorithm would code the 'Tweak' / 'Next Move' function (other than via a random combination of planning variables) in an application such as Employee Shift Rostering with a very large search space and with multiple planning variables. On the page (http://www.jboss.org/drools/drools-planner.html) where Drools Planner is compared side-by-side to other naive (greedy algorithms-based) approachesfor various kinds of problems, could it be the case that the algorithms used in Drools Planner were able to perfectly solve the highlighted problems only because of the use of extremely small search spaces / input datasets?! A wikipedia entry related to metaheuristic algorithms says that not only is it possible that such an algorithm may not give an optimal solution, it may not even give any solution at all(!!) due to the algorithm reaching its timeout limit specified by the user. I'm assuming it won't be possible to specify a timeout value in days or even hours for any metaheuristics-based approach to a real-world problem of a real-world scale. Lastly, from looking at the pseudocode of Tabu Search, it *appears* that the core, 'driver portion' of the algorithm may itself be not all that hard to implement; it is rather the call-back portion of the algorithm (such as the problem-specific Tweak / Next Move function, which the driver portion calls back) that may be hardest to implement. Given this, what would be the advantages of using Drools Planner over a from-scratch, hand-coded version of Tabu Search (other than its declarative, rule-based flexibility which a hand-coded, from-scratch version may not want to implement due to its focus on solving a specific planning problem vs. a whole slew of generic planning problems requiring a generic piece of code such as Drools Planner)? Would greatly appreciate if someone more knowlegeable than me could clarify / elaborate on the above getting-started questions of mine. Regards, /HS -- View this message in context: http://drools.46999.n3.nabble.com/Employee-Shift-Rostering-algorithm-deta... Sent from the Drools: User forum mailing list archive at Nabble.com.