how can I get constraints

回答済み

Cass C

2022年11月25日 17:16

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Hi,

I got some constraints as:

I want to get them by using getConstrByName(), however, this method chooses one arbitrarily. So is there any other way helps to obtain all constraints with the same name?

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  Jaromił Najman

  • Gurobi Staff

  2022年11月28日 15:38 編集済み

  Hi Cass,

  So is there any other way helps to obtain all constraints with the same name?

  No, there is no way to get all constraints with the same name at once. You could loop over all constraints and save the ones with the name of interest, e.g.,

  constrs_of_interest = []
  for c in m.getConstrs():
    if c.ConstrName == "c1":
      constrs_of_interest.append(c)

  In general, it is not recommended to have multiple constraints with the same name. You could adjust your current code to

  m.addConstr(Pf[(brh,t)], gb.GRB.LESS_EQUAL, branchPar[brh]['Limit'],name="c1{0}{1}".format(brh,t))

  You could then, later loop over \(\texttt{(brh,t)}\) and get all constraints by name.

  Or even better, you could save the constraints to a dictionary while constructing them.

  mydict = {}
  [...]
        mydict[brh,t] = m.addConstr(Pf[(brh,t)], gb.GRB.LESS_EQUAL, branchPar[brh]['Limit'],name="c1{0}{1}".format(brh,t))

  You can then access the constraints via \(\texttt{mydict[brh,t]}\) without having to retrieve them from the model again. Of course this only works, if your dictionary is in the same scope as your model.

  Best regards, 
  Jaromił

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  Cass C

  2022年11月28日 15:29

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  Hi Jaromił

  Many thanks for this, you are right! It should be formatted in list or dictionary, or it won't work.

  Best 

  Qikun

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