About the Matrix subtraction in gurobi

Answered

Yanbo Fan

June 25, 2021 12:42

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Hi, 

Can someone tell me how to express this constraint in gurobi? I didn't find a description in the API documentation. If you can help me, I will be very grateful to you. This is my constr.

This is my code. （q[j] - qr[j]） Subtraction between two matrices does not seem to be allowed in gurobi.

code

model = grb.Model('')
qr = np.array([[500, 500, 100], [500, -500, 100], [-500, 500, 100], [-500, -500, 100]])
s = np.array([[-250, -250, 0], [-250, 250, 0], [250, -250, 0], [250, 250, 0]])
q = model.addVars(4, 3, lb=-500, vtype=GRB.CONTINUOUS, name='q')
k = model.addVars(4, vtype=GRB.CONTINUOUS, name='k')

model.update()

for j in range(4)
  model.addConstr(k[j] <= np.linalg.norm(qr[j] - s[1]) ** 2 + 2 * (qr[j] - s[1]).transpose() *(q[j] - qr[j]))

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  June 23, 2025 02:52 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?.
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  Jaromił Najman

  • Gurobi Staff

  June 25, 2021 12:59

  Hi,

  It is currently not possible to perform vector operations with \(\texttt{Var}\) objects. However, you can always write vector operation as sums. In your case, this would be

  for j in range(4):
    model.addConstr(k[j] <= np.linalg.norm(qr[j] - s[1]) ** 2 + 2 * (grb.quicksum( (qr[j][i] - s[1][i])*(q[j,i] - qr[j][i]) for i in range(3))) )

  Best regards,
  Jaromił

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  Yanbo Fan

  June 26, 2021 05:00

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  Hi Jaromił, 

  Thank you for your detailed answer. Thanks to your help, I have successfully solved this problem now. 

  Best regards,

  Yanbo

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