Jacob Jin

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Activity overview

Latest activity by Jacob Jin

  • Jacob Jin commented,

    1. Community
    2. Algorithms
    3. Why the extreme ray Groubi retrieved is 0?

    Hi, I have fixed the error and retrieved the extreme ray.  The extreme ray is a 0-vector. 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?

    Answered
    1. Community
    2. Algorithms

    During 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...

    • Jacob Jin
    • 2 followers
    • 3 comments
    • 0 votes

  • Jacob Jin created a post,

    Can we change the linear expression's lines randomly in gurobi ??

    Answered
    1. Community
    2. Modeling

      lin_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
    • 2 followers
    • 1 comment
    • 0 votes

  • Jacob Jin commented,

    1. Community
    2. Programming
    3. change the coefficient of the variables in the objective function

    Thanks!

  • Jacob Jin commented,

    1. Community
    2. Programming
    3. change the coefficient of the variables in the objective function

    Hi Jaromil,    How could I reset the coefficient of a specific variable in a specific objective function when I deal with a multi-objectives problem in Gurobi?   Thank you so much!

  • Jacob Jin commented,

    1. Community
    2. Modeling
    3. Gurobi's Solvetime

    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,

    1. Community
    2. Modeling
    3. Gurobi's Solvetime

    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,

    1. Community
    2. Modeling
    3. Gurobi's Solvetime

    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,

    1. Community
    2. Modeling
    3. Gurobi's Solvetime

    Sorry for that. Here is the c202.txt.  https://drive.google.com/file/d/1sG4W6F2tGwZ7rTs-TVZOdHh-7FOweXYm/view?usp=sharing  Thank you!

  • Jacob Jin commented,

    1. Community
    2. Modeling
    3. Gurobi's Solvetime

    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....