Jacob Jin
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Latest activity by Jacob Jin
Jacob Jin commented,
Hi, I have fixed the error and retrieved the extreme ray. The extreme ray is a 0vector. It is abnormal. Why gurobi fail to give a valid extreme ray? Thank you so much.

Jacob Jin created a post,
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...

Jacob Jin created a post,
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(...

Jacob Jin commented,
Thanks!

Jacob Jin commented,
Hi Jaromil, How could I reset the coefficient of a specific variable in a specific objective function when I deal with a multiobjectives problem in Gurobi? Thank you so much!

Jacob Jin commented,
I find the point! from numpy import *import numpy as npimport pandas as pdimport gurobipy as gbfrom gurobipy import *from gurobipy import GRBfrom itertools import permutationsimport timeimport warn...

Jacob Jin commented,
Hi Jaromi, I have tried your suggestion but it didn't work. The thing I can ensure is that I didn't let the sub_dual problem be preresolved when I defined the objective function in the callback fun...

Jacob Jin commented,
Hi, Jaromił As for the difficulty we talked about, I realized that when I just set the sub_dual problem's presolve parameter as 1 in the callback function, the log result showed that the solver di...

Jacob Jin commented,
Sorry for that. Here is the c202.txt. https://drive.google.com/file/d/1sG4W6F2tGwZ7rTsTVZOdHh7FOweXYm/view?usp=sharing Thank you!

Jacob Jin commented,
Sorry, I didn't get your meaning about Could you please also incorporate this model change after the first iteration into your snippet to reproduce the issue? My core code: https://drive.google....