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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Verifying optimality for given primal and dual solutions to a linear program

Consider the following linear program: maximize $\sum\limits_{j = 1}^n {{p_j}{x_j}}$ subject to $\sum\limits_{j = 1}^n {{q_j}{x_j}} \le \beta$ $\begin{array}{*{20}{c}} {{x_j} \le 1}&{j = 1,2, \ldots…
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Expressing nonlinear problem as LP

I am using GLPK to solve a simple linear problem. Given is a set of distances $d_{ij}$ between nodes of a graph. We want to assign to each edge a velocity $v_{ij}$ such that the average time of travel per edge $\frac{1}{|G|}\sum_{i,j}…
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Linear Programming Inventory

A company is opening a new franchise and wants to try minimizing their quarterly cost using linear programming. Each of their workers gets paid 500 per quarter and works 3 contiguous quarters per year. Additionally, each worker can only make 50…
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Linear Optimization: What is the difference between these two theorems?

I attend a lecture about linear optimization where we had the following two Theorems. But I somehow cannot spot the difference: Theorem 1: Let $P$ be a polyhedron with an extreme Point and $c \in \mathbb{R}^n$ an objective function. Suppose that…
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Finding Optimal Value with Linear Programming Subroutine

I am stuck on this question: Consider the problem: $\underset{x}{\text{minimize}}{\frac{c^{T}x+d}{f^{T}x+g}}$ $\text{s.t. } Ax\leq b$ $f^{T}x+g>0$ Suppose we have prior knowledge that the optimal cost belongs to an interval [K,L]. Provide a…
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The meaning of initial value in linear programming

I am new to LPP. I would like to know what is meant by setting an initial value(IV) to a variable. For example I was solving a problem where objective function(OF) is non-negative. When I give some IV to a particular variable the OF is coming out to…
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About linear programming

Before to write my question. (P) linear programming, and the dual problem is denoted (P*). Th linear problem defined via matrix (m x n) matrix A. b is a vector in R^m and c in R^n. The program (P) can be written as: max_x∈R c*x under the constraints…
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Writing an unconstrained variable as an equality

I am working on some problems on the Simplex Algorithm for Linear Programming. In order to apply the simplex algorithm, the LP must be in standard form. If the constraint is an inequality with a $\leq$, then I just add a slack variable, $s_1\geq 0$.…
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Linear programming problem - do we have enough data here?

I am to solve a following problem, but it seems to me that it is ill-formulated, i.e. there's not enough data. Am I right? If not what would be the mathematical model for it? Every coffee table produced gives company 9\$ revenue. Every bookshelf -…
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Formulation of linear problem

I'd like to ask you how to formulate this problem as linear problem (equations)? Marie wants to buy oranges and apples. She has to buy at least 5 oranges and the number of oranges has to be less than 2 times number of apples. One orange weights 150…
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Linear programming with reuse of services

I came across some questions of this style and was not sure what the minimization function would be. A hotel requires a known number of hand towels for guests to be given during the week and the goal is to meet the demand at minimum cost. Suppose…
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Where did i go wrong in this linear inequation evaluation?

We are currently studying Linear Programming in school and while going through it i seem to of come across a ridiculous error. Problem is, i can't seem to find it. Essentially there is an equation 8 - x - y >= 0 (>= signifies greater than or equal…
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Enquiry to Linear Programming.

I came across this Theorem on Optimum solution to a Linear programming problem: " If $S$ is the feasible region of some linear program with objective function $ z=c^{T}\textbf{x}$ then 1) $z$ attains its optimal value at some vertex of $S$, 2) the…
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Can a feasible region have many 'parts'?

For example, could my constraints ever give me a feasible region composed of the unit square and a triangle with vertices (2,1), (3,1), (2,3)? (Edit: obviously this would never happen, but I am using this to illustrate what I mean by 'parts') My…
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Solving linear programming problems

Find the smallest value of the function $f=21x+14y$ considering only those values of $x$ and $y$ that satisfy the constraints \begin{eqnarray*} 15x + 22.5y &\geq& 90, \\ 810x + 270y &\geq& 1620, \\ x/9 + y/3 &\geq& 1, \\ x, y &\geq&…