New answers tagged vehicle-routing
0
votes
Gurobi spend more time in presolve in small model without removing anything
In the log you show, the Presolve parameter was changed to 2. That value corresponds to an aggressive setting. It can therefore be expected that presolve takes longer than when left at the default ...
- 346
3
votes
Gurobi spend more time in presolve in small model without removing anything
It is a general misconception that presolve reduces the size of the problem. While this is a typical side effect, the actual goal of the presolving step is to find an equivalent model that is more ...
- 1,588
1
vote
Implementing soft time window constraints with time_matrix dependent on vehicle types
I was able to fix this. I checked on following points:
time callback function must return an integer and not float.
You can not add time window constraints on depots.
...
- 201
0
votes
What's the best way to speed up Benders Decomposition for a stochastic vehicle routing problem?
Without knowing much about the problem, there are several approaches (listed in increasing difficulty of implementation):
1). Warm-start the model at a known feasible solution.
2). You could try ...
- 61
2
votes
Travelling salesman problem
The MTZ constraints are big-M constraints that enforce the logical implication
$$x_{ij}=1\implies u_j\ge u_i+d_j.$$
That is, if you traverse arc $(i,j)$, the cumulative demand at $j$ is at least the ...
- 30.5k
1
vote
Optimization algorithm for space debris
ACO, genetic algorithms and other metaheuristics can be adapted to constrained problems by adding to the objective function penalties for constraint violations and then treating the problem as ...
- 37.9k
2
votes
Scheduling & Routing Problem
One possibility might be to start by constructing feasible one-day schedules for techs (service just A, service A and B in some order, service A, B and C in that order, ...). The MILP model would then ...
- 37.9k
0
votes
Is there existing code for the set partitioning formulation of routing problems?
There is a Python interface for the VRPSolver that can be installed using the following code:
python -m pip install VRPSolverEasy
All the information is given in ...
- 8,622
1
vote
Is there existing code for the set partitioning formulation of routing problems?
Python is not an efficient language, and solving the resource constrained shortest path is the bottleneck of the branch-and-cut-and-price algorithms for routing problems. Therefore, you won't find a ...
- 2,495
Top 50 recent answers are included