Issue while modelling indicator constraints

回答済み

Vamsi Krishna

2023年11月30日 22:04

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I am trying to model the following constraint.

where x_ij is binary Decision variable, c_j is continuous decision variable, and k_i is parameter. K is set for the parameter k_i values K ={k_1,......, k_n}

# Indicator constraints for c[j] = K[i] implies z[i, j] = 1

for i in range(len(K)):

    for j in range(m):

        model.addConstr(c[j] - M[i] == 0 >> z[i, j] == 1, name='indi_constr_1')

        # Indicator constraints for c[j] != M[i] implies z[i, j] = 0

        model.addConstr(c[j] - M[i] != 0 >> z[i, j] == 0, name='indi_constr_2')

# Link z variables to x variables

for i in range(len(K)):

    for j in range(m):

        model.addConstr(z[i, j] == x[i, j], name="indi_constr_3")

 

For these constraints, I am getting the following error.

line 48, in <module>
    model.addConstr(c[j] - M[i] == 0 >> z[i, j] == 1, name=f"indicator_constraint_cj_mi_{i}_{j}")
TypeError: unsupported operand type(s) for >>: 'int' and 'Var'

Any help would be much appreciated.

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• 正式なコメント

  

  Simranjit Kaur

  • Gurobi Staff

  2026年11月13日 01:33

  This post is more than two 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.
• 

  Marika Karbstein

  • Gurobi Staff

  2023年12月01日 07:51

  There are several issues in your formulation

  1. The expressions in the indicator constraints (see Model.addGenConstrIndicator() ) need brackets, e.g., 
     

     model.addConstr((x7 == 1) >> (x1 + 2*x2 + x4 == 1.0))

  2. The indicator variable needs to be binary
  3. not-equal constraints are not supported

  So, you need to reformulate your expression. For example, c != k could be expressed as |c-k| >= eps.
  Note, to use Model.addGenConstrAbs() you will need helper variables.
  The following articles might be helpful

  • How do I model logical and general expressions?
  • Why doesn't Gurobi support strict inequality constraints like x < a?
  • How do I model conditional statements in Gurobi?

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