constrain error, "model.pxi"

Answered

Felipe Bofarull

July 08, 2020 06:13 Edited

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Hi, I am new to Gurobi and I don't know how to fix the error in #R3

 

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  June 23, 2025 03:10 Edited

  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 why not try our AI Gurobot?.
• 

  Felipe Bofarull

  July 08, 2020 06:13

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  from gurobipy import *
  import math
  
  #n = int(input('n = '))
  n = 4
  print(n)
  
  X = []
  
  for i in range(1,n+2):
      X.append(int(i))
  
  print(X)
  
  # Modelo
  of = Model()
  
  # Variables
  a = of.addVar(vtype=GRB.CONTINUOUS, name='a')
  x = {}
  y = {}
  for i in X:
      x[i] = of.addVar(vtype=GRB.CONTINUOUS, name='x')
      y[i] = of.addVar(vtype=GRB.CONTINUOUS, name='y')
  
  of.update()
  
  # Restricciones
  
  # R1
  for i in X:
      of.addConstr(x[i] >= 0)
      of.addConstr(y[i] >= 0)
      of.addConstr(a >= 0)
  
  # R2
  for i in X:
      of.addConstr(x[i] <= a)
  for i in X:
      of.addConstr(y[i] <= a)
  
  # R3
  for i in X:
      for j in X:
          if not i == j:
              of.addConstr(((x[j]-x[j])*(x[j]-x[j]) + (y[j]-y[i])*(y[j]-y[i])) >= 4)
  
  # Objetivo
  ob = 4 * a
  
  of.setObjective(ob, GRB.MINIMIZE)
  
  of.optimize()
  
  of.printAttr("X")

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• 

  Sonja Mars

  • Gurobi Staff

  July 08, 2020 06:30

  Can you clarify what exactly you mean by error? The code seems to be fine. Just the model that comes out of it, is non-convex. Gurobi can solve this kind of problem if you add 

  of.params.nonConvex=2 

  right before the call of 

  of.optimize()

  Best,

  Sonja

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