
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 0-vector. I write this model to an lp file, read and optimize...
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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(...
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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...
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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...
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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] ...
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How to use callback function within multi-objective 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...
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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]...