Accessing the reduced costs of the variables in each branch and bound tree
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I am using gurobipy 10 and I was wondering if there exists any commands that help me with the following problem:
At each node of branch and bound tree, I need to access the reduced cost of the variables in the optimal tablue. How should I define my callback function?
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It is currently not possible to access reduced costs of the node relaxation LP from a callback. Indeed, it is currently not possible to access the reduced costs of the node relaxation at all.
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Jaromił Najman
Could you please elaborate on the "impossibility to access reduced cost". The simplex method must update these reduced cost attributes anyway.0 -
Could you please elaborate on the "impossibility to access reduced cost". The simplex method must update these reduced cost attributes anyway.
It is correct that the Simplex method updates the reduced costs in every iteration. However, it does not mean that this information is available during every iteration. You can only access reduced costs after you have solved an LP.
During a MIP solve, it is not possible to access the node relaxation LP and thus, it is not possible to access the reduced costs of the node relaxation LP.
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