Questions tagged [or-tools]
Questions related to or-tools, Google's open-source software suite for optimization
122
questions
2
votes
1
answer
524
views
Using OR-Tools with .NET and GUROBI
We want to model our MILP problem with Google OR-Tools in .NET, and solve it using GUROBI (solver may change in the next 1-2 years). However, we couldn't find the correct syntax to call GUROBI.
https:/...
- 355
2
votes
1
answer
197
views
Scheduling when task duration longer than working interval
I'm trying to modify the job shop example for CP-SAT solver. (https://developers.google.com/optimization/scheduling/job_shop)
I'm limited to 8 hours working day,
So I defined a list of NewIntervalVar()...
- 65
2
votes
1
answer
524
views
Set value based on if other variable is in specific range
I have the following problem.
number_of_machines is controlled by other constraints. I need to set line variable to specific value based on "range" ...
- 65
1
vote
0
answers
264
views
Set Covering and Column Generation
I need some set covering and column generation examples in OR-Tools python.
If anyone can provide or direct me to some resources that would be great..!
- 137
2
votes
1
answer
195
views
A specific case of a resource constrained project scheduling problem with partially renewable resources (RCPSP/$\pi$) - OR-Tools
I've been trying solve a specific case of the resource constrained project scheduling problem with partially renewable resources (RCPSP/$\pi$ in the literature e.g. this paper). These resources are ...
- 168
1
vote
1
answer
73
views
Print Intermediate Solutions of Scheduling Problem and tackling FLAGS in jupyter notebook
I tried this code and it goes on and I'm clueless when it'll end so I manually interrupt it.
Is there any way we can see intermediate solutions that are feasible solutions and can we limit time or ...
- 137
2
votes
0
answers
128
views
Multiple Depot/Crew Office Bus Driver Scheduling Modelling
I'm working on Bus Driver Schedule with multiple add-on constraints that are complex and hence trying to figure out how this can be achieved.
Reference of Bus Driver Scheduling using OR-Tools:-
https:/...
- 21
3
votes
2
answers
231
views
Extracting CNF representation of my problem from SAT solver
As I know, any SAT solver such as or-tools or cplex cp optimizer converts a given problem to CNF form in the first place. Is it possible to extract the resulting CNF representation from or-tools or ...
- 39
2
votes
1
answer
201
views
OR-Tools, How to avoid dividing by zero
Problem: There is an order to fabricate some products of total number, let's say 200 (all products are the same). We have some number of factories, let's say 5. Every factory has different number of ...
- 65
4
votes
1
answer
741
views
Using VRPy and OR-tools in Python to solve the DCVRP
This question is a follow-up to this one.
Since I understand the complexity of the problem I have been underestimating, I turned my attention to off-the-shelf solvers, like VRPy and OR-tools. I would ...
- 1,239
4
votes
2
answers
359
views
OR-Tools: Partial Solution ignored due to "unknown rate is too large"
With SetHint() from the OR-tools linear solver I am trying to pass a feasible solution to my problem. But I receive the following warning:
...
- 93
3
votes
2
answers
2k
views
Travelling salesman problem variant without returning to the starting point
I tried the code provided on the link :
https://developers.google.com/optimization/routing/tsp
The actual requirement is to traverse all paths without returning to the start point with minimum ...
- 131
5
votes
2
answers
2k
views
find suboptimal solution, if no optimal solution exists?
I am using or-tools linear solver. and my problem ends up having no optimal solution. how can I tell the solver to find a suboptimal solution?
1
vote
0
answers
168
views
Modified bus scheduling problem question in ortools
Has been crossposted in stackoverflow. I want to solve the bus scheduling problem using ortools with some minor modifications. In my case, the max number of drivers is known. The modifications I would ...
- 153
0
votes
0
answers
126
views
Mixed Integer Programming - Model Formulation for A Resource Allocation Problem
There are a number of orders, which needs to be shipped. For each order, there may be 1 to 3 route options. The problem here is to find out the best allocation (combination) of orders among these ...
- 137
3
votes
0
answers
227
views
Add Variables in Bulk for ortools
I am using the Python ortools to solve large LPs where the number of variables and constraints are in the hundred thousands ($10^5$). Surprisingly, it takes longer ...
- 131
3
votes
1
answer
753
views
CP-SAT _ Summing variables under conditions
I have been working lately on scheduling optimization using CP-SAT in OR-TOOLS and now I'm at the point where I need to start considering due dates in my model.
I didn't want to put them as ...
- 119
1
vote
1
answer
582
views
Problem with setting up gurobi with OR-tools
I am trying to setup Gurobi with Google OR-Tools with the function pywraplp.Solver.CreateSolver("GUROBI"). The function returns None, which could occur if ...
- 21
2
votes
0
answers
408
views
modify pickup and delivery problem to only delivery scenario in google OR-tools
I am using Google OR Tools for solving the capacitated vehicle routing problem.I want to implement optimization solution for delivery problem.For example there is one storage location which load all ...
2
votes
2
answers
900
views
Cutting Stock Problem : Mixed Integer Programming
I am asked to solve the following problem:
The problem:
You were asked to repair a farm house with sheets of plywood.
You were given thirty sheets of plywood. (each size = 10ft x 10ft)
The house ...
- 29
3
votes
2
answers
170
views
Google OR returning different values depending on language
Lately, I have been working on a CP-SAT model for solving multi-resource flexible job shop problems.
I used the code (1) as an inspiration for building code (2) in Python which works well. Then I had ...
- 119
2
votes
2
answers
127
views
Parallel scheduling with precedence constraints and variable job length
I have $N$ jobs and $M$ machines and want to minimize the makespan, i.e. the total time to finish all jobs. Some jobs have precedence constraints and can only be started once other jobs are finished. ...
- 145
3
votes
1
answer
1k
views
Python, Google OR-Tools, OnlyEnforceIf() method
I am trying to solve a basic puzzle by using Google OR-Tools, this is my first try with OR-Tools and I am trying to learn. I completed almost everything and was ready to conclude the program until I ...
- 61
8
votes
2
answers
909
views
OR-TOOLS : delivery node with multiple possible pickup nodes
I am using ortools to model a VRP with pickup and delivery constraints, where pickups can be done at different nodes. For example, if node A has a demand, it must be picked at node B or C.
Here is how ...
- 12.3k
3
votes
0
answers
110
views
Production planning for a video game economy
I'm a software developer who likes to play a video game that has a complex economy. I realized that the type of problem I'm trying to solve mimics real life operations research problems, and I am ...
- 139
6
votes
1
answer
537
views
OR-TOOLS : is it possible to partially fulfill a demand?
I am working on a vehicle routing problem with or-tools.
Is it possible to partially fulfill a demand? I know it is possible to drop nodes with the disjunction constraints. But in this case, a node is ...
- 12.3k
2
votes
1
answer
1k
views
How to know which constraint in CP-SAT did not meet the feasibility gap
Is there any systematic way to retrieve some information on the constraint that caused infeasibility in Or.Tools CP-SAT?
...
- 117
2
votes
1
answer
109
views
How to model a set of integer variables getting assigned different values than another set of integer variables
Assume we have variables $x_1, x_2, x_3, x_4$ that each can belong to $\{1,2,...,10\}$. How can we model a constraint that variables $x_1, x_2$ get assigned different values than $x_3, x_4$?
Because ...
- 117
2
votes
3
answers
505
views
How to model two variables to NOT to belong to the same set partition using Constraint Programming
Assume we have two variables $x,y \in S$ where $S=\{1,2, \dots, 1000\}$.
Also, we are given a partition of set $S$ as:
$S_1 = \{1,2, \dots, 249\}$
$,S_2 = \{250, \dots, 499\}$
$,S_3 = \{500, \dots, ...
- 117
3
votes
0
answers
140
views
Best known results on the flexible jobshop benchmarks
Is there a website that compiles the best known results on the flexible jobshop problem ?
I know there was a blog post/article by Quintiq, a (deleted) blog post on CP Optimizer, some more recent ...
- 2,219
1
vote
1
answer
426
views
Flexible Job Shop Problem with several resources per alternative - Ortools
It has been quite a journey for me to go from 0 to understanding the job shop (js) and the flexible job shop (fjs) examples given by Google's ORTOOLS team.
Now the time has come for me to start ...
- 11
3
votes
0
answers
49
views
High-mix manufacturing capacity
I'm not an expert in OR but I would like to determine what is the maximum manufacturing capacity of a plant (or how much a plant can produce of mix products).
Each person in the plant has a known set ...
- 31
4
votes
1
answer
402
views
maximum number of BoolVar 's before or-tools is no longer feasible to use
The standard nurse scheduling problem which is used as an example for OR-Tools (see for example https://developers.google.com/optimization/scheduling/employee_scheduling) attempts to assign boolean ...
- 41
5
votes
1
answer
374
views
Best way to solve an allocation problem
I have the following problem: I have products with different attributes (price, weight, category) and I have a list of clients. Every client has an "affinity value" with every product, the ...
- 53
3
votes
1
answer
539
views
How to balance the workload of teachers in OR-Tools (maximization of the minimum)
I am very new to optimization and OR-Tools. I am trying to solve a very simple question.
Let's assume that we have $n$ students. Each student needs to be assigned to only one teacher as a supervisor. ...
- 31
5
votes
1
answer
372
views
Is it possible to solve VRP using OR-Tools CpModel, instead of RoutingModel?
Is it possible to solve VRP using OR-Tools CpModel, instead of RoutingModel? I want to do synchronized VRP, which is combining vehicle routing and scheduling constraints
- 261
6
votes
2
answers
554
views
Priority List Constraint
I used the Vehicle Routing Problem example that has the objective of minimizing total distance traveled for each vehicle.
Suppose that each order to pick up for each vehicle at each node has a ...
- 101
3
votes
2
answers
2k
views
How to add logical OR constraint in OR-Tools?
Let's say nurses normally do 1 shift
for d in all_days:
for s in all_shifts:
model.Add(sum(shifts[(n, d, s)] for n in all_nurses) == 1)
But I want to ...
- 261
1
vote
0
answers
185
views
Fixed cost associated to SlackVar(waiting time cost) [CVRPTW]
I'm modeling a CVRPTW with some features:
Each type of vehicle has a cost per km and a fixed cost per trip. To calculate these costs, I am using these methods for this:
...
- 111
4
votes
1
answer
466
views
Adding a hard and soft upper bound constraint of number of locations to visit (VRP)
I went through the Vehicle Routing Problem example and was able to replicate it. On the example, there is a constraint added for vehicle maximum distance as shown below:
...
- 101
9
votes
3
answers
2k
views
Open source MILP solver for quick “good enough” solution
I have a problem that I have already posted elsewhere in OR.stack, but the question is focused around a large binary MILP (about 1 million decision variables). Ultimately, I am more time constrained ...
- 325
7
votes
2
answers
2k
views
CP-SAT over CBC for MIP, is it worthwhile?
I am working in an integer optimization problem. All of the decision variables are binary, and the objective is to minimize some cost function. I currently am implementing CBC, but I have been reading ...
- 325
4
votes
1
answer
748
views
Solving vehicle routing problem in java
I am trying to solve vehicle routing problem in java and I am looking for libraries for the same. I did a POC using google or-tools and it seems to be solving all my use cases. I would like to know if ...
7
votes
1
answer
2k
views
CP-SAT ortools - Is there any complete list of possible/available StringParameters for the CpSolver?
I wonder if there is any list of string parameters documented.
So far, I only know max_time_in_seconds and num_search_workers.
...
3
votes
1
answer
477
views
Optimal way to ensure optional intervals are consecutive in OR-Tools
I am trying to solve a scheduling problem in OR-Tools. There are lots of "events" that need to be scheduled to "blocks" (essentially half-days). I am naturally using optional intervals for the events. ...
- 141
7
votes
1
answer
985
views
Solution time out for VRPTW in or-tools
I am experimenting around with or-tools and somehow I can't get a solution for the VRPTW problem for any of the instances I have tested from Gehring & Homberger ...
- 219
5
votes
2
answers
542
views
How to measure model quality in OR-Tools?
After creating my model for a problem, what steps should I take to test if a change in the model is actually helpful or not?
In Python, ...
- 1,384
4
votes
1
answer
879
views
How exactly does OptionalIntervalVar work in OR-Tools?
I created OptionalIntervals for a number of tasks:
...
4
votes
1
answer
660
views
TSP with constraints in OR Tools
I am completely new to OR Tools, but what I have tried so far seems very powerful.
I have, however, run into a problem that I cannot seem to figure out how to solve.
I am trying to model a TSP ...
- 61
5
votes
1
answer
1k
views
assigning values to IntVar if and only if BoolVar, else zero [or-tools]
If I have an IntVar s[j] stored in a vector s, is it possible to iterate for (a period of ...