Simranjit Kaur

Hi, Unfortunately, it is not possible to write lazy constraints or user cuts added via callback with Model.write() function directly. However, you can workaround this by tracking the lazy constrain...

Hi Qiru, Please introduce an auxiliary variable y, and replace the constraint MODEL.addConstr(b[2]*e1 + b[4]*e2 + b[7]*e3 == gb.max_([b[k] for k in range(0, 8)]) ) with the following y = MODEL.addV...

Hi Qiru, The error “gurobipy.GurobiError: Variable has not yet been added to the model” happens due to Gurobi’s lazy update approach, precisely when we try to access and use a variable before updat...

Hi Dagm, In general, to model a product of n variables, you will need to add (n-1) auxiliary variables and constraints as described in How do I model multilinear terms in Gurobi? However, from your...

Hi Myat, The error  "KeyError: 'Missing constraint index'" occurs when you try to add a single constraint using the method Model.addConstrs(). Please use Model.addConstr() instead of using Model.ad...

Hi Dagm, The error is coming from constraint 'a22' in your example, as it contains a product of three variables. Modelling multilinear terms directly is not supported in Gurobi at present.  However...

Hi Siqi, To model your objective function, specifically the term x^(1-z), we will need to use Gurobi’s general constraints. Let’s see how this can be done. x^(1-z) is same as exp( (1-z)*log(x) ). T...

Hi, The behaviour you are observing occurs mostly when a model has numerical issues. Numerical issues can sometimes result in the simplex algorithm declaring the model infeasible while the IIS cons...

Hi Siqi Zhang, The method model.addVars() returns a tupledict. You should use ox_2[i,h,l] instead of ox_2[i][h][l] to access the variable associated with the tuple (i,h,l), as shown below: for i in...

Hi Ramesh, To ensure that D is zero when the binary variable C is zero, you can add another indicator constraint:  m.addConstr( (C==0) >> (D==0) ) Alternatively, you can add a Big-M constraint, m.a...