Decision Optimization

Decision Optimization

Delivers prescriptive analytics capabilities and decision intelligence to improve decision-making.


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  • 1.  Closer to the optimal solution

    Posted 08/06/18 10:56 AM

    Originally posted by: Janisch


    Hello,

    enclosed you will find my model file, the data file and the excel file. My problem is that the solutions that the algorithm spends after 10 minutes unfortunately have a gap of 85%. My question is, of course, whether one can reduce this gap as much as possible. There does not have to be an optimal solution. Does anyone know maybe programming optimizations.

    Now to my problem formulation:
    This is a permutation flow shop problem with 20 stations and 210 products. The products have different processing times at the respective stations. At a cycle time of 120 seconds, it sometimes happens that some processing times are greater than 120 seconds. The stations are also 120 seconds long, but can be larger and smaller, depending on whether drift is allowed. The algorithm should now determine the size of the stations (workstations) and the order of the products so that the least possible overload occurs. Overload means that the worker at the station can not complete the job and a jumper must finish the unfinished work. There are two workplaces per station which are covered. At every workplace a worker works.

    I hope you can understand my explanation of the optimization problem. If there are questions ask. Maybe I forgot something to explain :)

     

    regards


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  • 2.  Re: Closer to the optimal solution

    Posted 08/09/18 07:38 AM

    Originally posted by: GGR


    Hi

     

    The gap calculated by the engine, particularly in constraint programming with a sum of large variable  is a very not reliable information.

     

    In your case you should rather compare the incumbent with your own indicator.

     

     

    Hope that help

     


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  • 3.  Re: Closer to the optimal solution

    Posted 08/09/18 01:10 PM

    Originally posted by: Janisch


    So you do not mind to improve the performance a bit?
    But the lower limit indicates the optimum in my problem. Since I want it as close as possible to it :)


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  • 4.  Re: Closer to the optimal solution

    Posted 08/11/18 02:56 PM

    Originally posted by: Janisch


    Can I influence the branch decision (see attached file)? If so, how can I program this?


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  • 5.  Re: Closer to the optimal solution

    Posted 08/13/18 07:42 AM

    Originally posted by: rdumeur


    Dear Janish,

     

    You can influence the branch decision by specifying search phases.

    Please have a look at the sched_square.mod example in the OPL distribution and read the documentation there: https://www.ibm.com/support/knowledgecenter/SSSA5P_12.7.1/ilog.odms.ide.help/OPL_Studio/opllanguser/topics/opl_languser_shortTour_CP_search.html

     

    Cheers,

     

           Renaud

     


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