Questions tagged [or-tools]

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

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4
votes
2answers
353 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
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0answers
33 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 ...
0
votes
0answers
74 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 ...
2
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0answers
33 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 ...
1
vote
1answer
56 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 ...
1
vote
1answer
67 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 ...
2
votes
0answers
128 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
2answers
286 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 ...
3
votes
2answers
141 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 ...
7
votes
0answers
210 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 ...
3
votes
0answers
101 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 ...
6
votes
1answer
174 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 ...
2
votes
1answer
308 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
94 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 ...
2
votes
3answers
273 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, ...
4
votes
0answers
74 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 ...
1
vote
1answer
84 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 ...
2
votes
0answers
42 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 ...
4
votes
1answer
101 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
209 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 ...
1
vote
1answer
111 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. ...
4
votes
1answer
135 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
5
votes
2answers
186 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 ...
3
votes
2answers
486 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 ...
1
vote
0answers
65 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: ...
4
votes
1answer
137 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
2answers
440 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
253 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
1answer
453 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
1answer
114 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. ...
6
votes
1answer
462 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 ...
5
votes
2answers
354 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, ...
4
votes
1answer
178 views

How exactly does OptionalIntervalVar work in OR-Tools?

I created OptionalIntervals for a number of tasks: ...
5
votes
1answer
243 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 ...
5
votes
1answer
476 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 ...
6
votes
0answers
114 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
118 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 ...
3
votes
1answer
120 views

ValidateModel or tools in c++ and proto problems

I'm trying to validate my model, this is the relevant part of my code: ...
5
votes
0answers
80 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+...
5
votes
1answer
584 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 ...
8
votes
1answer
202 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 ...
3
votes
0answers
106 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 $c_j$ ...
9
votes
1answer
474 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
1answer
601 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: ...
6
votes
1answer
508 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 \\ ...
10
votes
1answer
429 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 ...
11
votes
1answer
926 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: ...
7
votes
1answer
233 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 ...
8
votes
3answers
676 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, ...
4
votes
1answer
261 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 ...