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3 votes
2 answers
427 views

How to formulate this in gurobi

I have subtour elimination constraint but can't understand and formulate this in gurobipy. How to formulate this ? $$ \sum_{i \in S} \sum_{j \in S} x_{i j}^{v} \leq|S|-1 \quad v=1, \ldots, m ; S \...
overboxed's user avatar
  • 593
3 votes
0 answers
76 views

Linearization of a quadratic model, what is the difference while using gurobi?

I have a quadratic model of parking $N$ cars in $S$ separate lanes as follows. Each car has an arrival time and a departure time. Departure follow the last in first out principle. The objective is to ...
OR Junior's user avatar
  • 521
2 votes
3 answers
422 views

"Re-optimize" feature in Commercial Optimization

How does the "re-optimize" feature work in commercial optimization solvers such as IBM CPLEX and Gurobi? I recently experienced a considerable performance boost by re-solving a model with ...
Pia MiA's user avatar
  • 392
2 votes
1 answer
236 views

Implementing subtour constraints to a VRP in python

Hi I have a problem related to the vehicle routing problem, where I want to implement the subtour constraints $\sum_{(i,j)\in S} x_{ij} \leq \lvert S \rvert - r(S), \: \forall S \subseteq N, S > 2$ ...
Magnus M's user avatar
2 votes
1 answer
107 views

Construction heuristic for SDCVRP

I'm not sure how I should formulate this question as precisely as possible but at the same time retaining as much specific information as possible but I'll have a go. I have implemented a (Split ...
Parseval's user avatar
  • 207
2 votes
1 answer
58 views

How does a ratio of fixed cost to variable cost affect the problem difficulty?

I am working on an OR scheduling problem where OR opening cost is considered a fixed cost when a surgery is scheduled. If OR is used beyond a certain time, overtime cost is incurred. I would like to ...
Amogh Bhosekar's user avatar
1 vote
2 answers
506 views

Subtour elimination in SDVRP

I have the model below, based on this paper. It's a vehicle routing problem with split deliveries, i.e the locations/customers can be visited by multiple vehicles that share the demand at that vehicle....
Parseval's user avatar
  • 207
0 votes
0 answers
165 views

Lower bound very bad. How to improve?

I have the following MILP: \begin{alignat}{2} \nonumber \mbox{minimize } \quad & \phi = \sum_{i=1}^{m-1} \sum_{f=1}^{F} \sum_{\underset{\bar{f} \neq f}{\bar{f}=1}}^F \sum_{h \in H} \left( D_{f \...
Angelo Aliano Filho's user avatar