objective function with nested sum

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Maryam Azani

2022年06月07日 15:27

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I have an objective function with multiple operations for which I tried nesting with help of quicksum (below):

X, I, Y, and B are model variables

I have tried the following code which works but the answer is not correct. seems something in the prioritization of operations goes wrong but I cannot detect where.

 

obj1 = gp.quicksum((I[month,item] - v[item]) * h[item] * X[month,item] 
                     for item in items
                     for month in months
                     if month >= months[a +1])
obj2 = gp.quicksum((B[month,item] + v[item]) * p[item] * Y[month,item] 
                     for item in items
                     for month in months
                     if month >= months[a +1])
    
obj = obj1 + obj2
LP.setObjective(obj, GRB.MINIMIZE)

P.S. I have tried https://support.gurobi.com/hc/en-us/community/posts/4413382171921-Values-of-parts-of-objective-function as well but the code gives error.

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• 正式なコメント

  

  Simranjit Kaur

  • Gurobi Staff

  2025年11月16日 23:35

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.
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  Maliheh Aramon

  • Gurobi Staff

  2022年06月08日 05:33

  Hi Maryam, 

  It is hard to know what has gone wrong. Could you please clarify the following in the mathematical expression?

  1. The argument of the \(\mbox{min}\) function is \(r_i(t)\), but there is no variable named \(r_i(t)\) in the expression.
  2. The first sum goes over \(s\) but there is no variable in the expression that depends on \(s\). I assume that \(s\) represents what you are referring to as \(\texttt{months}\), but what \(a\) is then?
  3. The first term starts from \(s=0\) and the second term starts from \(s=1\), but in the code, both terms apparently are summed over the same set of \(s\) values (months).

  Best regards,

  Maliheh

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