Hans Kirchner
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Latest activity by Hans Kirchner-
Hans Kirchner commented,
It should be noted that running the model with Presolve turned off does not make the model infeasible or unbounded: gurobi_cl Presolve=0 minimal_example_genconstr_and.rew.gz Optimal solution fo...
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Hans Kirchner commented,
I uploaded my model with general-AND constraints to your file uploader at https://www.gurobi.com/upload-a-model/ I hope that was the correct way. The file is named: minimal_example_genconstr_and....
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Hans Kirchner commented,
I have a relatively small minimal example, once with the built-in "_and" and once with my custom "logical_and". Both models are clearly feasible but with the built-in "_and" I get this "max general...
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Hans Kirchner created a post,
Using addGenConstrAnd leads to "max general constraint violation"
AnsweredRecently I tested my Gurobi implementation on larger problem instances. But I got: Warning: max constraint violation (1.0000e+00) exceeds toleranceWarning: max general constraint violation (1.000...
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Hans Kirchner commented,
> What do you mean by "sometimes you just see"? I had a programming mistake that probably led to sometimes making a full and sometimes a partial MIP start. Thanks for the other answers. I still...
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Hans Kirchner created a post,
Different MIP start outputs
OngoingHi, I'm trying to give gurobi a MIP Start after my first optimization step. I set the Start to be the solution of every variable: for v in m.getVars(): v.Start = v.X For any new variable creat...
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Hans Kirchner commented,
I found my mistake: My piecewise-linear function was actually not convex (although just very slightly). Because of that the objective values were a bit off. That means that setPWLObj() can work wit...
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Hans Kirchner commented,
Yes, I'm minimizing and they are always convex! I implemented this and it performs great, even a bit better than setPWLObj. I ran model again for 30 minutes and the objective went down from 3897 to...
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Hans Kirchner commented,
Thanks for quick answer! Ok, I've tried to replace setPWLObj with a custom implementation based on the article you suggested. So I'm mapping all the "x"-values to "y"-values with lambda-variables a...
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Hans Kirchner created a post,
How to use PWL and Multi-Objectives together
AnsweredHi, I'm using gurobipy and I want to model two optimization steps. In the first step I just have a linear objective and in the second step I want to use some piecewise linear objectives. Is there a...