Jonasz Staszek

1. Community
2. Algorithms
3. Branch and Bound

Hi Iason, I take it you are a beginner in this field - I would then recommend these resources: LP Tutorial MILP Tutorial Hope this helps. Best regardsJonasz

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• Jonasz Staszek
• February 13, 2023 06:10
• 0 votes

1. Community
2. Algorithms
3. Check heuristics for each solution

A trivial code example would be: import gurobipy as gp def mycallback(model, where): if where == GRB.Callback.MIPSOL solution = model.cbGetSolution(model._vars) model._solutions[mo...

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• Jonasz Staszek
• February 10, 2023 11:23
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1. Community
2. Algorithms
3. Check heuristics for each solution

Hi Ana, technically applying your heuristic and function could be done from within a callback every time you get a feasible solution. But since the solver has no clue about the other function which...

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• Jonasz Staszek
• February 10, 2023 08:59
• Edited
• 1 vote

1. Community
2. Modeling
3. Why Variable is not in model after model.copy()

Hi Runfeng, in Gurobi a variable is an object which is tied to a model instance. Whenever you create a new model instance (e.g. by copying or creating a presolved model) you also generate "new" var...

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• Jonasz Staszek
• February 07, 2023 13:21
• 0 votes

1. Community
2. Modeling
3. Form a new variable from the subset of original variable (maximum values)

Hi Luka, you may be after generating one variable for each subset for which you look for a maximum and then adding a max general constraint. I would try something along the lines of: meritorder = g...

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• Jonasz Staszek
• February 07, 2023 10:05
• Edited
• 0 votes

1. Community
2. Modeling
3. Form a new variable from the subset of original variable (maximum values)

Thanks for pointing this out - my code was meant to be a rough guideline. Now, we have a correct piece of code for future reference. Best regardsJonasz

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• Jonasz Staszek
• February 07, 2023 10:04
• 0 votes

1. Community
2. Algorithms
3. Is it possible to return the initial problem gap without solving it?

Hi Alex, if you are only interested in the initial gap, then you might be happy taking the first feasible solution found by Gurobi, as well as the value of the bound. This can be done by setting th...

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• Jonasz Staszek
• February 03, 2023 11:04
• 0 votes

1. Community
2. Programming
3. Dynamic model

Dear Bahar, as far as I can see, you are solving five models. You do that in a sequential fashion, so you can't properly define all of them upfront - you can most likely only properly define the fi...

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• Jonasz Staszek
• February 02, 2023 09:50
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• 0 votes

1. Community
2. Algorithms
3. Convex combination of constraints that makes the problem infeasible

Hi Xuan, IIS - as per its definition - is a minimal system of constraints which together cause infeasibility. They are "equally important" - if you remove any of them, the system (but not necessari...

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• Jonasz Staszek
• February 01, 2023 11:05
• 0 votes

1. Community
2. Programming
3. Dynamic model

Hi Bahar, based on the description you provided it is difficult to understand what exactly is the difficulty you are dealing with. Could you please provide us with a minimal reproducible example of...

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• Jonasz Staszek
• January 31, 2023 08:50
• 0 votes