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Operations Research : Recent Questions and Answers (Page 6)

Find answers to your questions about Operations Research or help others by answering their Operations Research questions.

Formulating these logical constraint in an ILP

I have these two constraints : $z leq My$ $t leq M'y $ where $z$ and $t$ are two integer variables $ z, tgeq 0$,...

Asked on 01/18/2021

1 answer

Modeling the multiplication of two binary decision variables in undirected graph in python

In an undirected graph, I'm trying to model a constraint that forcing the optimizer to set an edge $(u,v)$ between two nodes to only exist (= $1$) if...

Asked on 01/18/2021 by Amedeo

0 answer

Flexible Job Shop with Preemption

I'm trying to solve a flexible job shop problem variant that has precedence constraints on jobs along with a few other issues. We have a MIP formulation and also a...

Asked on 01/15/2021 by Robert Hildebrand

0 answer

How to handle an equality constraint in metaheuristic algorithms (like GA, PSO)?

Metaheuristic algorithms are generally used to find the optimal solution to unconstrained optimization problems. I would like to maximize $x_1+3x_2-x_3ge0$ while respecting the equality constraint $x_1+x_2=5$. How can...

Asked on 01/11/2021 by stevGates

3 answer

What is the difference between min- cut formulation and (bi) partitioning formulation?

I have a min-cut formulation and a bi-partitioning problem.The two problems focus on finding the minimal cut value separating the two partitions?So what are really the differences between...

Asked on 01/08/2021 by fathese

1 answer

Logical constraint in ILP

I want to write the following constraint: Let $z$ be an integer variable such that $0le zle M$, and $t$ be a binary variable where $M$...

Asked on 12/22/2020 by che

1 answer

Quasi-convex function must be "partially monotonic"?

$f(x)$ is quasi-convex, $$x^*inargmin_{xin C}f(x).$$ How to prove that, for any $ain C$, $f(x) $ is weakly monotonic in the direction of $(x^*-a)$? Is this...

Asked on 12/13/2020 by High GPA

1 answer

Constraint programming resources

I am looking for resources to learn constraint programming. I will divide the resources I am looking for in three types: ModelingIs there resources (books, articles, courses, etc.) that...

Asked on 11/28/2020 by Joffrey L.

3 answer

Pyomo variable creation dilemma

I am working on a pyomo model, and need to create a few different sets of variables that are dependent on a solution from a master model. I need...

Asked on 10/31/2020 by Ethan Deakins

1 answer

Convexity of the variance of a mixture distribution

$X$ is a random variable that is sampled from the mixture of uniform distributions. In other words:$$X sim sum_{i=1}^N w_i cdot mathbb{U}(x_i, x_{i+1}),$$where $mathbb{U}(x_i, x_{i+1})$...

Asked on 09/25/2020 by independentvariable

1 answer

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