Questions tagged [or-tools]
Questions related to or-tools, Google's open-source software suite for optimization
135
questions
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What is the purpose of libraries like Pyomo and Google OR tools?
I'm new to the OR world, and trying to learn the various tools available. I originally thought that Pyomo and Google OR tools were open source alternatives to commercial solvers like Gurobi or CPLEX.
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- 2,089
16
votes
1
answer
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Warm start CPLEX using google or-tools
I have been trying to use the SetHint python API in google or-tools to warm start MIPs and solve it using CPLEX. It looks like my hints are accepted by the SetHint function but I am not sure whether ...
11
votes
1
answer
2k
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Incorrect solution for Vehicle Routing Problem in or-tools
I am trying to understand how the Vehicle Routing Problem is solved in OR-Tools.
Using the example given here, I have tried to solve the following distance matrix with 9 separate vehicles:
...
- 211
11
votes
1
answer
708
views
How to solve the Cumulative Traveling Salesman Problem using or-tools in python?
The objective of the Cumulative Traveling Salesman Problem (CTSP) is to minimize the sum of arrival times at customers, instead of the total travelling time. This is different than minimizing the ...
11
votes
1
answer
469
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Modeling an assignment/scheduling problem to minimize total wait
I have an assignment type problem in which there is a set of students, $S$, and a set of training classes $T$. Each training has a fixed start and end day and can accommodate at most 1 student. In ...
- 111
10
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1
answer
1k
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Floating points in ORtools
I'm trying to solve an RCPSPDc model (maximizing the net present value instead of a makespan). The objective function is: $\sum\limits_{j \in \text{Tasks}} e^{-\theta\cdot s_{j}}\cdot p_{j}$, where $...
9
votes
3
answers
4k
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Google - OR tools for workforce scheduling problems
Has anyone used the google OR tools in python to solve the workforce scheduling problem. Can you please let me know
Advantages and Disadvantages
Any issues faced during usage and implementation
9
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3
answers
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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
9
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1
answer
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TSP problem: traveller does not visit all nodes - Google OR-tools
Context:
I am dealing with a kind of scheduling problem, in which I have a set of tasks and machines. All tasks must be assigned to machines (not necessary all of them). In addition to that, I must ...
- 1,133
8
votes
3
answers
1k
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Maximize assigned tasks to each worker
In a scheduling problem I want to assign the maximum number of tasks to one worker before assigning it to another. For example, if I have $10$ tasks and $2$ workers, the best assignment would be $(10, ...
- 1,404
8
votes
1
answer
744
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Travelling salesman problem with given number of locations to visit
There's a great example here of how to find a solution to the travelling salesman problem:
...
- 271
8
votes
1
answer
445
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Precedence Constraint in OR-Tools
I'm trying to write this constraint in C++ and add it to my model (addLessOrEqual):
$$\text{start}_{i}+\text{duration}_{i}\le\text{start}_{j}$$ for an $(i,j)$ arc ...
8
votes
1
answer
188
views
Strategy for filling a table only slightly dependant on the number of columns
I'm using the OR-Tools CP-SAT solver to fill a table with integers, with various constraints, as illustrated by the x in the following figure.
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- 235
8
votes
2
answers
1k
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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 ...
- 12.8k
7
votes
2
answers
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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
7
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1
answer
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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.
...
7
votes
1
answer
1k
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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
7
votes
2
answers
609
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CP Framework/Solver for .Net Core
First I want to say that I'm very new to this field.
As far as I understand it, there are two different ways to use a Constraint Programming (CP) Solver:
Using the API from the Solver itself. For ...
- 343
7
votes
1
answer
391
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Shipments consolidation - how to model mutually exclusive items with OR-Tools CP Solver in Python (multi-knapsack, updated)
I am implementing a solution for packages consolidation (basing on Nurse Problem solution) with OR-Tools CP Solver.
There is a factory that manufactures some small Packages that need to be ...
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6
votes
1
answer
370
views
How to Model Path Being Only Through Adjacent Cells
I am trying to develop a MILP for a path planning problem. I am operating on a grid of cells that represents a map. The arrangement of cells in the grid represents the placement of the cells in real ...
- 325
6
votes
2
answers
606
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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
6
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1
answer
1k
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Constraint Programming OR-Tools finding Matrix Combinations
As a similar post of mine Find all Combinations of a Matrix I am trying to find matrix combinations with entries $>0$ meaning for a matrix
\begin{bmatrix}
0 & 1 & 3 \\
5 & 2 & 1 \\
...
- 1,193
6
votes
1
answer
736
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Python "Coffee Shop Scheduling Problem" - Scheduling Lunches/Breaks
I'm working on an employee scheduling program in python. Having never done this before, I've been researching different libraries that can be used to accomplish the task.
Unfortunately, none of the ...
- 63
6
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1
answer
699
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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 ...
- 12.8k
6
votes
0
answers
203
views
OptionalIntervalVar enforced but not working OR-TOOLS
I'm using OptionalIntervalVar and then maximizing the starts. The optimal solution is not affecting the other variables that creates the ...
6
votes
0
answers
156
views
Modelling issue with precedence constraint in OR-Tools
I'm trying to solve an RCPSPDc model It is infeasible, although Ilog Cplex solves it, so I think I have a modelling issue. I have more constraints but the precedence is the one that makes it ...
5
votes
3
answers
451
views
Maximize the minimal distance between true variables in a list
I'm using the OR-Tools CP-SAT solver on a list of $n$ boolean variables $x_i$. I'm trying to maximize the minimal distance between two true variables in this list, as illustrated by the following ...
- 235
5
votes
2
answers
2k
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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?
5
votes
2
answers
587
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, ...
- 1,404
5
votes
1
answer
2k
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Cumulative Constraint OR-Tools
I'm trying to solve an rcpsp model.
I can't find documentation for the AddCumulative function of OR-Tools. How should this function be used?
I want to write this ...
5
votes
1
answer
2k
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 ...
5
votes
1
answer
399
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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 ...
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5
votes
1
answer
409
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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
5
votes
1
answer
709
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How does OR-Tools improve on an initial solution to CVRP?
I have an initial solution to a CVRP instance which I am setting as input to the solver. The solver as expected returns an improved solution. I have a few questions regarding the solver.
How does the ...
- 91
4
votes
2
answers
431
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
4
votes
1
answer
270
views
Relevance of order of model construction in CP-SAT
Question 1: Is ortool's CP-SAT sensitive to the order in which a model is constructed?
In other words, does it matter which variables and constraints come first?
I am seeing a high performance ...
- 181
4
votes
1
answer
442
views
Is Google's OR-tools for professional work? Specially VRP module [closed]
So I've been given at work a project which consist on finding optimal pathing for trucks in certain custom scenarios. When I discovered this tool I thought it worked wonders for what I understood the ...
4
votes
1
answer
525
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:
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- 101
4
votes
1
answer
1k
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How exactly does OptionalIntervalVar work in OR-Tools?
I created OptionalIntervals for a number of tasks:
...
4
votes
1
answer
803
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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
1
answer
477
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 ...
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4
votes
1
answer
547
views
Can I print the linear programming sensitivity analysis report using google or-tools?
One can solve the linear programs using google or-tools with GLOP solver. I wonder if there is a way to print the sensitivity report (like shadow prices etc.).
4
votes
1
answer
703
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
4
votes
1
answer
798
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 ...
4
votes
1
answer
424
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Machine Allocation & optimal Utilization using python
Problem statement: Meet the demand which can be met across 2 facilities each having multiple machines where several components are made. The objective is to find the optimal solution to meet the ...
- 141
4
votes
0
answers
653
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Google-OR tools vs Pyomo and other commercial Solvers for solving a simple maximum flow problem
I have implemented a Pyomo model for solving maximum flow problem as a subroutine of an algorithm. However, the approach does not scale very well because Pyomo does not provide a very good way to re-...
- 392
4
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0
answers
101
views
Modelling issue with rcpsp and boolean expressions
I'm trying to solve an RCPSPDc problem in OR-Tools with CP-SAT solver.
In my RCPSPDc model (with discount rate) i want to set this objective:
$$\max_{s}\sum_{j\in J}\text{profit}_{j}\cdot \frac{1}{(1+...
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
3
votes
2
answers
250
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
3
votes
2
answers
3k
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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