Questions tagged [constraint-programming]

For questions on modeling satisfaction or optimization problems in languages designed for expressing (often high-level) constraints on decision variables.

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2
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1answer
22 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" ...
2
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1answer
32 views

ILOG CPOptimizer soft constraints (multiple solves reusing searched space)

I'm trying to feed information retrieved from my neural network to my CP model to help narrow down the search on big instances of my problem. However, I also want to remove the additional imposed ...
3
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0answers
47 views

Convex Optimization Problem with norm inequality constraint

Consider the following optimization problem: \begin{align} \inf_{x,y}&\quad(x-x_0)^\top A(x-x_0) + (y-y_0)^\top B(y-y_0) \\\text{s.t.}&\quad x^\top a\geq0,\\ & \quad y^\top b\geq0, \\& ...
8
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2answers
206 views

VRP through constraint programming

I am with a problem that consists of determining whether a VRP instance is feasible, this question is a continuation of an older thread. In order to do it, I was thinking of using Constraint ...
1
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1answer
81 views

Dual of quadratic program with linear objective

Let $c$ and $k$ be element-wise positive $n\times 1$ vectors and let $A$ be a element-wise positive and positive-definite matrix. Consider the optimization problem \begin{align} \max_{p\in\mathbb{R}^n}...
1
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1answer
52 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 ...
2
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0answers
99 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:/...
4
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1answer
111 views

How do I formulate constraints that check if a parameter is between certain values, using binary variables?

I have $3$ parameters $a_1,a_2,a_3$ and a variable $d$ and $3$ binary variables $b_1,b_2,b_3$ and a "result" variable $s$. How do I model constraints so that: If $d$ is between $0$ and $a_1$...
2
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0answers
56 views

Consistency Level of Constraints

recently I started using CP and translated my first MIP model into a CP model with the IBM CP Optimizer. Lately I was confronted with a question I could not answer: "What is the consistency level ...
2
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1answer
71 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 ...
5
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1answer
256 views

Solving Quadratically Constrained Quadratic Program with Cross Product Terms Only

I'm totally new to the world of optimization and I have an optimization problem that I think it can be formulated as Mixed Integer Quadratically Constrained Quadratic Program (QCQP) but I'm not sure ...
5
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1answer
124 views

Solver Recommendation : Discrete Variables and Quadratic Constraints

I would like some solver recommendations to solve a problem with boolean/integer variables, mostly linear constraints but also some quadratic constraints. I also have an objective to minimize which is ...
-4
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1answer
102 views

Multiple If else constraints in Mixed integer programming

How to formulate the following as constraints in MILP? a[0][0] = y, if x[0]= 0, a[0][0] = 0, if x[0] != 0, . . . . a[i][j] = b[i][j-1] + y, if x[j]=i, a[i][j] = a[i][j-1], if x[j] != i, ... . . . b[0]...
2
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1answer
123 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 ...
5
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4answers
443 views

How to visit a subset of network nodes in a single trip?

I have a connected network where I want to visit a set of destinations which may require visiting intermediate nodes as well because there may be no direct edge between source and destination nodes. I ...
4
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1answer
321 views

Is there any automatic way to spot contradictory constraints in linear programming?

Let's have the following trivial linear program: \begin{align}\max&\quad z=20A+30B\\\text{s.t.}&\quad A\le60\\&\quad B\le50\\&\quad A+2B\ge220\\&\quad A,B\ge0\end{align} It's easy ...
4
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2answers
185 views

Scheduling optimisation constraint on consecutive shifts & consecutive night shifts (`python`)

I am trying to write a program to schedule a team of 8 individuals into shifts. I want to know how to model that every individual must get at least one night shift break, and must not work two ...
2
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2answers
95 views

Scheduling: Tasks changing the state of the executing machine

I have a scheduling problem in which machines consume their battery when executing tasks and charge their battery when not executing tasks. A single task has to be executed in one go (no recharging ...
0
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1answer
48 views

What is a good approach to deciding which jobs (from a list of HPC jobs) should be ran locally vs. on the cloud given time & cost constraints?

Cloud computing has transformed the landscape of compute operations. Of course, there are still many labs/businesses with local, large-scale compute clusters. For those businesses who keep the ...
3
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2answers
196 views

Modeling in integer programming vs modeling in constraint programming

I have some experience with linear and integer programming modeling (I read Model Building In Mathematical Programming by Williams). Now I am trying to learn how to model with constraint programming. ...
1
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1answer
243 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 ...
0
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2answers
213 views

How can I formulate this specific if-then constraint?

IF $\sum\limits_d X_{i,d}\ge6$ THEN $Y_i = 1$ (strictly) AND IF $\sum\limits_d X_{i,d}<6$ THEN $Y_i = 0$ (strictly) $X$ and $Y$ are binary variables. What I'm actually trying to do is to charge the ...
1
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1answer
112 views

Constraint programming and scheduling issues

I have a constraint problem that I need to resolve, but I did not how know to model the problem: I have 11 employees, I will name them from $a$ to $k$: $\{a,b,c,d,e,f,g,h,i,j,k\}$. I have a small ...
2
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1answer
465 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
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1answer
96 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
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3answers
286 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
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1answer
106 views

Any references to the ROADEF 2020 Challenge?

The problem description of the challenge is given here. Does anyone has some references to similar problem. I would like to participate but I don't know where to start.
8
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1answer
439 views

Adding a constraint in constraint programming

Is it true that the more we add constraint to a constraint programming solver the more efficient it will be? How does this compare to adding constraints in integer programming solvers.
3
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2answers
684 views

What are the solvers that give a feasible solution within a given time?

What are the solvers that take the maximal computation time as a parameter and gives the best found feasible solution within this time.
2
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1answer
86 views

Looking for a similar optimization problem

I want to know if there is any already defined problem that could give me a hint on how should I approach the following task. There are N tasks that should be accomplished, each task requires ...
1
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3answers
280 views

How can I linearize this IF-THEN constraint?

Let $P_{t,u}; t=1,2,\ldots,T, u=1,2,\ldots,U$ be known values $\alpha$ is also a known parameter $X_{t,u}$ an optimization variable I have the following constraint: IF $P_{t,u}\geq\alpha$, THEN $X_{...
3
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1answer
83 views

Integer decision variables as index

The following problem has only two integer variables; however, they appear in the index of the parameters. Appreciate it if anyone has any efficient idea to transform it into a canonical integer ...
8
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3answers
294 views

Constraint programming resources

I am looking for resources to learn constraint programming. I will divide the resources I am looking for in three types: Modeling Is there resources (books, articles, courses, etc.) that are ...
3
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1answer
186 views

Mixed integer programming vs Constraint programming

I see that certain studies are comparing MIP and constraint programming (CP) performances. And generally, they claim that CP outperforms MIP. But I believe that it is not completely true. Because ...
2
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0answers
69 views

Finding Optimal Route using different Paths

I have a list of paths e.g. path 1 takes you from point A to B. A person needs to complete 5 of such paths. $$Route1 = path1 + ...
2
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0answers
156 views

Operation hours optimization for circular schedule

Here is my problem. A store has X = 15 electical devices with the ability to work non-stop, fully charged, up to 8 hours. Their battery charge lasts 2 hours and the operating hours of the store differ ...
3
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2answers
142 views

Limit number of switches in employee scheduling problem

Here is a scheduling problem I need to solve. Given the demand for 2 positions in 1 week with 3 shifts per position, I need to allocate the employees accordingly with some extra operational ...
2
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0answers
47 views

Algorithm for Trainyard Marshall optimization problem

The problem I am trying to solve is the 2014 RAS problem. The link is the following The problem Trains come to the humpyard where each compartment of a train gets humped or disassembled and then each ...
5
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3answers
197 views

How can I optimize this integer programming constraint problem without running out of memory?

I am trying to run this constraint problem but the memory runs out, $$S_{i}$$ are 1975 Students that need to be assigned to one of 188 teacher assistants classes, each teacher assistant has to chose a ...
1
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0answers
82 views

Question on quadratically constrained quadratic program

If the constrained optimization problem is a quadratically constrained quadratic program of the form \begin{align}\min&\quad x^HQx-a(x+x^H)+b|z^Hx|^2\\\text{s.t.}&\quad\|x\|^2\le1\end{align} ...
1
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0answers
71 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: ...
7
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1answer
1k views

How to use the least number of colours to colour different routes of a bus route such that no two intersecting routes will have the same colour

I would like to know of a method in which if provided say 10 routes with details regarding which route intersects with which another route, we can use the least number of colours to colour the routes, ...
1
vote
1answer
70 views

Derived variables of when a decision variable appears?

I am dealing with a multi-travelling passenger problem. $x_{i,j}$ is a binary variable that allocate a passenger $i$ to a vehicle $j$, every vehicle can carry only $n_{pv}$ passenger where $i \in \{1,...
3
votes
2answers
159 views

Could DOcplex.CP recognize that it solves the graph coloring minimization problem?

I created a graph coloring DOcplex.CP model inspired by this example. However, I do not know the number of colors in advance. The goal is to minimize the number of colors (i.e., get as close as ...
3
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1answer
94 views

How to convert non-normal probabilistic constraints to deterministic ones for mathematical modelling?

I am working on a chance-constrained optimisation model that takes into account uncertainty. I am aware of how to convert constraints that are of a probabilistic nature into the equivalent ...
3
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1answer
127 views
8
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2answers
183 views

Which MiniZinc-compatible solvers are best suited for floating decision variables and non-linear constraints?

We are working on a production scheduling problem that has both discrete ("how much to produce from good x and where") and continuous elements ("keep the workload of a production site below 0.7"), ...
6
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2answers
121 views

Are there some benchmark problems for CSP Solvers?

I am building my own CSP solver with simple backtracking, AC3 filtering and variable/value ordering heuristics. It supports non binary constraints. I've done some good progress and I'd like to ...
7
votes
1answer
637 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. ...
4
votes
1answer
108 views

Constraint programming in OPL: intervals covering time slots

I am trying to model the following: There is a shop open from xx AM to yy PM. In each 30 min time slot, there have to be demand[timeSlot] = x employees present. E.g. the shop is open from 08am to ...