How do I Add a constraint that a variable have to be multiple of 12?

Answered

Simon Maturana

October 19, 2020 22:33

• 
• 

In my problem, y have capacities per hour that are multiple of 12, so the answers have to be multiples of 12 too.

I was planning to use something like this: m.addConstr(F1%12==0,name="c_147")

 

But I get this Error:

TypeError                                 Traceback (most recent call last)
<ipython-input-186-37db67e1659a> in <module>
----> 1 m.addConstr(F1%12==0,name="c_147")
      2 m.addConstr(F2%12==0,name="c_148")
      3 m.addConstr(F3%12==0,name="c_149")
      4 m.addConstr(F4%12==0,name="c_150")
      5 m.addConstr(F5%12==0,name="c_151")

TypeError: unsupported operand type(s) for %: 'Var' and 'int'

Can you please help me?

0

• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  June 23, 2025 03:06 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?.
• 

  Eli Towle

  • Gurobi Staff

  October 19, 2020 23:22

  The modulo operation isn't directly supported. However, you can model this constraint by introducing an auxiliary integer variable \( \texttt{u1} \) and setting \( \texttt{F1} \) equal to 12 times \( \texttt{u1} \):

  u1 = m.addVar(vtype='I', name='u1')
  m.addConstr(F1 == 12*u1)

  Because \( \texttt{u1} \) is an integer variable, \( \texttt{F1} \) must be equal to some multiple of 12.

  By the way, you might find Model.addVars() and Model.addConstrs() useful for building the model more concisely. E.g.:

  F = m.addVars(5, name='F')
  u = m.addVars(5, name='u')
  m.addConstrs((F[i] == 12*u[i] for i in range(5)), name='modulo')

  0

Post is closed for comments.