Jacob Jin
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Recent activity by Jacob Jin
Why the extreme ray Groubi retrieved is 0?
AnsweredDuring the callback process(benders decomposition), for one step, when the dual is unbounded, the unbounded ray retrieved by Gorubi is 0vector. I write this model to an lp file, read and optimize...

Can we change the linear expression's lines randomly in gurobi ??
Answeredlin_exp_2 = K * sum( z_dual[i, l].x * model.getVarByName('z_' + str(i) + '_' + str(l)) for l in L for i in range(N + 1))+ K * sum(r_dual[i, j].x * model.getVarByName('r_' + str(i) + '_' + str(...

Gurobi's Solvetime
AnsweredHi, I defined a linear model and then defined its objective function. After I solved it, I redefined its objective function. I found that the second solve time I derived from Runtime was much large...

Can the callback function combine two check mechanism?(TSP subtour elimination + Bender's decomposition)
AnsweredHello, I use callback function to optimize a MIP problem. if where == GRB.Callback.MIPSOL: selected = gb.tuplelist((i, j) for i in range(N + 1) for j in range(N + 1) i...

Is the TSP example's code in Gurobi documentation wrong???
AnsweredThis is the code in the tsp example: if len(tour) < n: # add subtour elimination constr. for every pair of cities in tour model.cbLazy(gp.quicksum(model._vars[i, j] ...

How to use callback function within multiobjective optimization?
AnsweredI want to use Hierarchical method to to solve a MIP problem with 2 objective functions. And when I optimize with the higher priority objective function, I want to use callback method. How should we...

How to add a matrix variable to a matrix/array?
Awaiting user inputI have defined an array and a matrix variable in the concrete model. Then I add the constraint below. However, "Incompatible dimension" is casted. What's wrong with my code? y_i = [[3, 2, 1, 1, 2]...