Questions tagged [linear-programming]

Questions on linear programming, the optimization of a linear function subject to linear constraints.

A linear programming problem may be defined as the problem of maximizing or minimizing a linear function subject to linear constraints. The constraints may be equalities or inequalities.

Linear programs are problems that can be expressed in canonical form as \begin{align}\max\quad&c^\top x\\\text{s.t.}\quad& Ax\le b\\\quad& x\ge 0\end{align} where $x$ represents the vector of variables (to be determined), $c$ and $b$ are vectors of (known) coefficients, $A$ is a (known) matrix of coefficients, and ${\displaystyle (\cdot )^{\top}}$ is the matrix transpose.

The expression to be maximized or minimized is called the objective function ($c^{\top}x$ in this case).

The inequalities $Ax \le b$ and $x \ge 0$ are the constraints which specify a convex polytope over which the objective function is to be optimized. The inequality $x \ge 0$ is called non-negativity constraints and are often found in linear programming problems. The other inequality $Ax \le b$ is called the main constraints.

Applications:

Linear programming can be applied to various fields of study. It is widely used in mathematics, and to a lesser extent in business, economics, and for some engineering problems. Industries that use linear programming models include transportation, energy, telecommunications, and manufacturing. It has proven useful in modeling diverse types of problems in planning, routing, scheduling, assignment, and design.

References:

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How to solve an overdetermined system of linear inequalities?

I want to solve an overdetermined system of inequalities ($ax+by \ge c$). Specifically, I have $10$ linear functions of the form $ax+by$ that must be bigger than $c$ at a point $(x,y)$. But it is good to minimize the difference between $ax+by$ and…
FarmBoy
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Linear Programming problem with absolute values

Consider a linear optimization problem, with absolute values, of the following form: \begin{equation} \begin{array}{rl} \text{minimize}\ &\mathbf{c'x}+\mathbf{d'y}\\ \text{subject to}\…
Qwerto
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Preconditioning linear program

I have a linear program $$ \text{minimize } c^T x \text{ subject to } Ax \geq b $$ where $A$ is of the form $$ A = \begin{pmatrix} A_1 \\ A_2 \end{pmatrix} $$ with $A_1$ well-conditioned and $A_2$ well-conditioned up to a positive diagonal scaling…
gTcV
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How to formulate non smooth function with an if statement as a linear program?

$f(a) = \begin{cases} a & a \ge 1 \\ 2a-1 & a\lt 1 \end{cases}$ $\text{minimize } f(u_1) + f(u_2)$ $\begin{align*} \text{s.t. } &\text{some constraints involving } u_1, u_2\\ & \text{some constraints involving } f(u_1), f(u_2) \end{align*}$ I know…
samol
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Why does branch and bround in linear integer programming converge?

So, we solve a relaxation of the integer program. We get a solution. It is not integer. So we create branches where in each new branch, we form appropriate bounds to rule out the non-integer solution. We repeat. Okay. ... why does this converge? My…
merija
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Help with binary variable

I need to make a constraint for the following condition: Among students 1, 2, 3, and 4, at least two of them must be on the team, if there are any on the team at all. I have defined Y1, Y2, Y3, and Y4 to be 1 if student i is on the team and 0 if…
icobes
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Linear programming modelling question

The problem is: A production company requires different amounts of renewable resource on different days of the week. The units of renewable resource required on each day is given as follows: Monday: $17$ Tuesday: $13$ Wednesday: $15$ Thursday: $19$…
nelsun
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Binary linear programming with two-dimensional parameter

I am trying to solve a linear programming problem like the following, where $x_i$ represents a binary decision to purchase or not product $i$, and $a_i$ is the utility of product $i$: $$max \sum_{i=1}^n a_ix_i$$ However, I also have a $n\times n$…
mathiascg
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concentration constraint for knapsack problem

I do have a question related to a 0-1 knapsack problem: I formulated a model with quite a lot of constraints and an objective function on maximizing “balance”. I solved the problem using one of the available commercial solvers (lindo systems).…
Peter
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identifying if constraints are binding, non-binding or redundant visually

Say you're given a linear program graphed with multiple constraints, and you're asked to identify which are binding, non-binding or redundant just by looking at the graph. A redundant constraint is easiest to see as it is one that does not…
H4-math
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Linear programming Convex Polyhedron

When we define the contraints for a linear programming problem we get that the domain is a Convex Polyhedron . But, i think it's possibile to add also an equality contraint, in this way the domain of the linear programming can turn into a line. Is…
Qwerto
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Convex combination of extreme points

The question asks me to "show that if the optimal value of the objective function of a linear programming problem is attained at several extreme points, then it is also attained at any convex combination of these extreme points." I try to write a…
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Show that $ \ x_ 0 \ $ cannot be an optimal solution

Consider the LP maximize $ \large z = cx \ $ subject to $ \ Ax ≤ b \ , x ≥ 0 \ $ where $ \ c \ $ is a nonzero vector. Suppose that the point $ \ x_ 0 \ $ is such that $ \ Ax_ 0 < b \ $ and $ \ x_ 0 > 0 \ $. Show that $ \ x_ 0 \ $ cannot be an…
MAS
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The reason behind a WRONG solution to a linear programming problem

I have two different solutions for the following LPP: "Suppose that $f(x)=ax+b$.If $f(0)\leq2,f(1)\geq0,f(2)\leq4$ find maximum value of $f(10)$" Solution 1(Correct): $$f(10)=10a+b=9(2a+b)-8(a+b)\leq 9\times4-8\times0=36$$ Solution…
Hamid Reza Ebrahimi
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Convert implication to linear constraint

I have the next constraint in logic (simplified): $$\forall r \in R, t \in T: x_{rt} = 1 \implies t_a < r_p < t_b$$ I need to linearize this. What I've come up with is: \begin{align} x_{rt}t_a &< r_p \\ x_{rt}r_p &< t_b \end{align} But this looks…