Decision Optimization

Decision Optimization

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  • 1.  Problem with equation Solving

    Posted Tue September 02, 2014 05:29 PM

    Originally posted by: Michi123


    Good day, I would like to solve the following problem in CPLEX:
     
    int u [1..V] [1..V] = ...;
    int M = 51000;
    int b [1..V] = ...; interval upper limit
    int a [1..V] = ...; Interval lower bound
    dvar int d [1..V];
    dvar int w [1..V];
    dvar int m [1..V];
    dvar boolean x [1..V] [1..V];
     
     
    Equation 1:
     
    forall (i in 2..V, j in 1..V)
    d [i] + u [i] [j] - (M * (1-x [i] [j])) <= d [j]
     
    Equation 2:
     
    forall (i in 2..V)
    b [i] + m [i]> = d [i];
     
    Equation 3:
     
    forall (i in 2..V)
    a [i] -w [i] <= d [i];
     
    This is only a section of the whole mathematical model.
    It is a Traveling Salesman Problem, which works with travel times instead of distances and to meet so-called time window.
     
    The problem is that CPLEX simply the limits b [i] into equation 1 set, and m [i] to zero and continues to calculate. however CEPLEX should, only calculate the equation 1, and then check the equation 2 and 3, and thus then it could calculate m [i] and w [i].
    m [i] and w [i] is then, namely, required for the objective function, which includes x.
     
    Could you please tell me maybe how I can solve the problem or how to correct formula should read in CPLEX?

    #CPLEXOptimizers
    #DecisionOptimization


  • 2.  Re: Problem with equation Solving

    Posted Mon September 15, 2014 10:24 AM

    Um, sorry. I don't understand what your problem is. I don't even see any b or m in equation 1.

    Could you please try to rephrase your question or explain in more detail what is going wrong?


    #CPLEXOptimizers
    #DecisionOptimization


  • 3.  Re: Problem with equation Solving

    Posted Mon September 15, 2014 11:34 AM

    Originally posted by: Michi123


    Yes, I try it. 
     
    In Equation 2, m [i] and d [i] is a variable only b [i] is given (in .data file). 
    Now CPLEX selects m [i] and set it zero and set d [i] equal to b [i].

     But actually he should calculate with the equation 1 d [i] and only then consider equation 2. And afer, as now d [i] and b [i] are given calculate m [i].

     I hope I have expressed myself now more understandable many greetings and thanks for your reply / response.

     

    The overall problem I have written in the article Topic: Traveling Salesman (TSP) with soft Time Windows and IBM ILOG CPLEX , but that I no longer believe a mathematical problem:-) Fals however find a solution directly for that I would certainly be happy:-) 


    #CPLEXOptimizers
    #DecisionOptimization


  • 4.  Re: Problem with equation Solving

    Posted Thu September 18, 2014 02:18 AM

    I am still not sure I understand correctly. First of all, CPLEX does not consider constraints one by one. It always considers all constraints simultaneously.

    Are you saying that m[i]=0 is an infeasible solution or is it just that you did expect another solution?


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    #DecisionOptimization


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