Carl Baier
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Activity overview
Latest activity by Carl Baier-
Carl Baier created a post,
Non-convergence in lexicographic column generation
AnsweredHello. i have the following problem with the the following lexicographical model. The master problems look like this:$C_i^v\) and \(\chi_{itk}^v\) are parameter in the MPs and \(\lambda_{iv}\) and ...
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Carl Baier created a post,
Farkas Pricing doesnt lead to feasibility
I am currently trying to initialize my column generation in the root node with Farkas Pricing. I am starting with a completely empty model. My model will look like this. Where \(\Lambda_{ij}\) is t...
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Carl Baier commented,
Ronald van der Velden I just stumbled upon this post. I am a bit confused right now. How can i add a variable if the model has already been fixed? Suppose i have my master problem and initialize it...
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Carl Baier created a post,
C1P/TU check in Gurobi
AnsweredHello, I wanted to ask if there is a possibility with Gurobi to check if the constraint matrix A has Total Unimodular (TU) or the Consecutive ones property (C1P). Thank you!
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Carl Baier created a post,
Branch-n-price implementation complications
I have the following problem. I have a Nurse Rostering problem that is difficult to solve in reasonable time with large instances (and additional constraints, which I omit here for complexity reaso...
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Carl Baier commented,
Jaromił Najman Hi. I have a new conical problem which appearance. I want to read and analyze all solutions from the solution pool of optimal solutions. For this I use this code. for k in range(m...
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Carl Baier commented,
Jaromił Najman I know, and I did relax the model before solving it, but sadly it still doesn't work. The computation of the other dual values does work however, as I can print them out if I call th...
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Carl Baier commented,
Jaromił Najman Sorry, its me again. I recently tried to aggregate all my subproblems into one and use an aggregated formulation of the master problem. To do this, I got rid of the index \(i\) in bo...
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Carl Baier commented,
Jaromił Najman Well its weird since isnt infeasible but i just cant compute the duals. Any further ideas why that can be?
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Carl Baier commented,
Jaromił Najman I did some testing and noticed something strange. I copied the Demand_Dict once and multiplied all values by 0.1. If I now use the constraint: def generateConstraints(self): for ...