Questions tagged [or-tools]

Questions related to or-tools, Google's open-source software suite for optimization

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17
votes
1answer
786 views

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
1answer
1k views

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: ...
11
votes
1answer
464 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
1answer
272 views

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 ...
10
votes
1answer
441 views

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 ...
9
votes
3answers
3k views

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
votes
1answer
549 views

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 $...
8
votes
3answers
721 views

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, ...
8
votes
1answer
618 views

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: ...
8
votes
1answer
234 views

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
1answer
154 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. ...
7
votes
1answer
561 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. ...
7
votes
2answers
353 views

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 ...
7
votes
1answer
250 views

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 ...
7
votes
0answers
307 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 ...
6
votes
1answer
546 views

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 \\ ...
6
votes
1answer
190 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 ...
6
votes
1answer
512 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 ...
6
votes
0answers
118 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
0answers
120 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
2answers
371 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, ...
5
votes
1answer
733 views

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
2answers
224 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 ...
5
votes
1answer
585 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
0answers
82 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+...
4
votes
2answers
403 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?
4
votes
2answers
550 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 ...
4
votes
1answer
158 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: ...
4
votes
1answer
168 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 ...
4
votes
1answer
107 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 ...
4
votes
1answer
156 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
4
votes
1answer
220 views

How exactly does OptionalIntervalVar work in OR-Tools?

I created OptionalIntervals for a number of tasks: ...
4
votes
1answer
270 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 ...
4
votes
1answer
288 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
1answer
217 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 ...
4
votes
1answer
279 views

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 ...
3
votes
2answers
583 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 ...
3
votes
1answer
137 views

ValidateModel or tools in c++ and proto problems

I'm trying to validate my model, this is the relevant part of my code: ...
3
votes
2answers
143 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 ...
3
votes
1answer
123 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. ...
3
votes
0answers
103 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 ...
3
votes
0answers
80 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 ...
3
votes
0answers
110 views

Power of variable or tools

I'm working with OR Tools in Python and I need to define the objective function an expression of the variables. In particular, the objective function is $$\frac{c_j}{1.7^{s_j}}$$ with $c_j$ ...
2
votes
3answers
282 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, ...
2
votes
1answer
112 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 ...
2
votes
2answers
96 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: ...
2
votes
2answers
298 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 ...
2
votes
1answer
405 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? ...
2
votes
1answer
60 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 ...
2
votes
1answer
95 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 ...