Some problem about adding indicator constraints

回答済み

hongyan liu

2020年03月18日 09:17

• 
• 
• 

I want to add constraints as below:

if dep[i][j] == 1 then z[0, j] < z[0, i]   0<i<4,i<j<4

I write these codes :

m.addConstrs((dep[i][j] == 1) >> (z[0, j] < z[0, i]) for i in range(tab_cnt - 1) for j in range(i + 1, tab_cnt)) 

Something wrong arise:

Traceback (most recent call last):
  File "/Users/hyliu/Documents/workspace/mapping/test.py", line 30, in <module>
    m.addConstrs((dep[i][j] == 1) >> (z[0, j] < z[0, i]) for i in range(tab_cnt - 1) for j in range(i + 1, tab_cnt))
  File "model.pxi", line 3336, in gurobipy.Model.addConstrs
  File "/Users/hyliu/Documents/workspace/mapping/test.py", line 30, in <genexpr>
    m.addConstrs((dep[i][j] == 1) >> (z[0, j] < z[0, i]) for i in range(tab_cnt - 1) for j in range(i + 1, tab_cnt))
TypeError: '<' not supported between instances of 'Var' and 'Var' 

Here is the definition of my variables:

tab_cnt = 4

dep = [
    [0, 1, 1, 1],
    [0, 0, 0, 0],
    [0, 0, 0, 1],
    [0, 0, 0, 0]
]

x = m.addVars(4, 4, vtype=GRB.BINARY, name='x')
y = m.addVars(1, 4, vtype=GRB.BINARY, name='y')
z = m.addVars(1, 4, vtype=GRB.INTEGER, name='z')

Thanks a lot!

1

• 正式なコメント

  

  Simranjit Kaur

  • Gurobi Staff

  2025年06月23日 03:16 編集済み

  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?.
• 

  Eli Towle

  • Gurobi Staff

  2020年03月18日 18:00 編集済み

  Hi Hongyan,

  First, note that < (strict inequality) is not supported for constraints. Perhaps you mean to use <= ( \( \leq \) )?

  Second, indicator constraints should be used when you want to say something like "if a binary variable is equal to 1, then this constraint should be enforced." In this case, dep isn't a variable in the model, but rather a list of values. If you only want to add constraints corresponding to the nonzero values in dep, you could instead include an if condition in your loop:

  m.addConstrs((z[0, j] <= z[0, i]) for i in range(tab_cnt - 1) for j in range(i + 1, tab_cnt) if dep[i][j] == 1)

  I hope this helps. Thanks!

  Eli

  0
• 

  hongyan liu

  2020年03月21日 07:53

  • 
  • 
  • 

  Thank you very much for your help, it really works.

  0

投稿コメントは受け付けていません。