Koen Timmermans
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Latest activity by Koen Timmermans
Koen Timmermans commented,
Hi Mario, Thank you for your explanation! Based on your Git repository I have changed my formulation to one without using the index k for the vehicles. This reduced the number of variables, constra...

Koen Timmermans created a post,
Improving model formulation and solving time
AnsweredHi! I have a task scheduling problem that I'm trying to solve using a MILP model. It closely resembles a VRPTW (Vehicle Routing Problem with Time Windows). The exact model formulation can be found ...

Koen Timmermans commented,
Hi Simran, Thanks for the quick reply! From what you explain, I understand why it is difficult for Gurobi to use my MIP start values for an initial feasible solution. I can make some changes to my ...

Koen Timmermans commented,
Hi Silke, Thank you for the quick reply! Unfortunately, the first link in your message is not working for me. And thank you for your recommended approach. If I understand you correctly, Model.cbPro...

Koen Timmermans created a post,
MIP start did not produce a new incumbent solution with a feasible MIPStart
AnsweredHi, I am using a selfwritten heuristic to find an initial feasible solution that I can provide to Gurobi as a MIPStart. After that I use the NoRelHeur to improve the solution before solving it fur...

Koen Timmermans created a post,
Changing the NoRelHeurTime parameter for the NoRel Heuristic using Callbacks
OngoingHi, I'm using the No Relaxation heuristic to quickly find feasible solutions for my optimization problem, which works very well. I was wondering whether it is possible to change the NoRelHeurTime p...

Koen Timmermans commented,
Dear Simran, Thank you for the fast and elaborate answer! VRPTW are often complex problems to solve. One direction could be to play with the most important parameters that impact the performance o...

Koen Timmermans created a post,
Improving solving (gap closing) time
AnsweredHi! I have a task scheduling problem that I'm trying to solve using a MILP model. It closely resembles a VRPTW (Vehicle Routing Problem with Time Windows). I use binary decision variable \(x_{ijk}\...

Koen Timmermans created a post,
Adding constraint in gurobipypandas with arrays of different lengths
AnsweredHi, Using \(\texttt{gurobipypandas}\), I want to create the following constraint: \[ z_{k} \geq y_{ik} \quad \forall i \in A, k \in K \] I have created y like this (ik_values_y as a multi index): ...

Koen Timmermans commented,
Hi Riley, Thank you for your quick response! I hadn't thought about "reindexing" in this way yet. I will try to implement it! Best regards, Koen Timmermans