# All Questions

813 questions
Filter by
Sorted by
Tagged with
4 views

### How to write a LP/MIP to cut unsorted list into bins with a minimum interval?

I have a list like this. ...
38 views

### VRP benchmark instances with charging stations

Are there any benchmark instances for VRP with charging stations? I also have various delivery points with charging stations in the city(Multiple Vehicles). How can I compare my formulation?
176 views

### Scheduling problem data generation

I compare the strengths and weaknesses of paradigms and approaches within those paradigms for solving machine scheduling problems. The amount of real-world data I have is limited and (random) ...
42 views

### Benders subproblem feasible region dependent upon solution master problem

Suppose I want to solve a naturally MINLP problem of the following form: $$\min_{x,y} \{c'x + y \mid Ax \leq b, Dx + Ey \leq f, G(x)y\leq g, x \in \mathbb{Z}, y \in \mathbb{R}^+\}$$ Here $G(x)$ ...
24 views

### MWIS on the 2-section of a specific uniform linear hypergraph

I have cross-posted the question from cstheory since it also very much fits the OR domain. My question concerns the maximum weight independent set (MWIS) problem on a certain (but "nice") graph. In ...
83 views

### Which solver solves PSD constrained convex non-linear problem

I have a problem with a vector variable $w \in \mathbb{R}^n$ and a symmetric matrix variable $V \in \mathbb{R^{n \times n}}$. I am solving a problem which is roughly like: \begin{align} \begin{array}{...
403 views

### Is there a better way to formulate this constraint?

Let $x_{r}^{j}=1\iff$ the machine schedules job $j$ using resource $r$. My constraint says that: a resource cannot be used twice, i.e., if $x_{r}^{j}=1$, then $x_{r}^{j'}=0$ for $j'\neq j$. I write ...
103 views

### How to exploit known solution in MILP

I have an MILP model to which I get an integer feasible solution as a result of a heuristic search. In this particular example, the initial solution turns out to be the optimal solution, which I prove ...
69 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"), ...
56 views

34 views

### Help with constrained or regularized optimization problem involving variable matrices and powers of matrices (or perhaps matrix logarithms)

I am attempting to solve the following optimization problem: $$\small\min_{A,B,C} \| Y_A - AX_A \|_F + \| Y_B - BX_B \|_F + \| Y_C - CX_C \|_F + \lambda_1 \|B - A^2\|_F + \lambda_2 \|C - A^4\|_F$$ ...
46 views

### Integer variable optimization - decreasing execution time

I have a variable declared as follows in AMPL: ...
70 views

### Linear programming explanation in Algorithms by Sanjoy Dasgupta

I am reading about simplex algorithms in a textbook titled Algorithms by Dasgupta-Papadimitriou-Vairani. On each iteration, simplex has two tasks: Check whether the current vertex is ...
101 views

### Can Gurobi or CPLEX handle nonlinearly constrained problems?

Though my title is quite general (please feel free to edit), indeed, I wonder if the following models can be solved in Gurobi or CPLEX. Model 2 is just an alternative one to Model 1. Although we ...
36 views

### Sales Impact Corona Infections [closed]

Given a company's sales per day and the number of corona infections are there good models that help us to predict the future sales increase or decrease, i.e. good model(s) showing the correlation ...
52 views

### Strong Duality and Slater Condition

I am studying the Duality Chapter of Convex Optimization by Boyd. Is it possible that strong duality holds for non-convex optimization? If yes, is there any specific condition? And, what is the ...
48 views

### Find the number of idle intervals with weights

We have one job $i$ and one machine. Let $\mathbf{x}_i=[x_{i,1},x_{i,2},\ldots,x_{i,T}]$ be a binary vector where $x_{i,t}=1\iff$ job $i$ is scheduled at time $t$. Let $u$ be a positive number. I ...
76 views

### Transforming a Quadratic constraint to SOCP

I have a problem similar to Markowitz portfolio optimization that I would like to transform into second-order cone programming. I have a linear objective function with a quadratic constraint (assuming ...
139 views

### Find the cheapest shopping cart

Given a list of items to buy on an e-commerce, generate the cheapest possible cart (which obviously includes all the items). The items can be purchased from many sellers at different prices. Sellers ...
100 views

### Concavity: Definition similar to sub-modularity

We know that for $b \geq a$, and some $s \geq 0$, a concave function $f$ satisfies: $f(a+s) - f(a) \geq f(b+s) - f(b)$. This is not a frequent definition of concavity, but can be found, e.g., here....
1k views

### IF X = 0 THEN Y = 1, IF X > 0 THEN Y => 0

I'm trying to model the following IF $tS = 0$ THEN $Y = 1$, IF $tS \gt 0$ THEN $Y \ge 0$ $tS$ is a positive real number and $Y$ is binary. I tried the following: $tS - \epsilon \ge -M Y$ but ...
133 views

### Operations Research Apps for everyday use

Since I am confined and I have some free time, I am looking for ideas of OR applications in everyday life. What I've seen so far are apps like solving VRP, Production planning etc. that are mostly ...
70 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 ...
70 views

### How to communicate number of integer combinations to a user

I'm working on a nifty little feature for our next release, i.e., to print the number of possible integer combinations left during branch and bound. This is really handy for the user because they ...
105 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 ...