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 matrix inequation $Mx \leq 0$?

While trying to model the relation between offers and exchanges in economics, I reached the point where I need to solve the following: Given a fat real matrix $M$ (more columns than rows), find all vectors $x \geq 0$ such that $Mx \leq 0$. The…
Amenhotep
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What is the relationship between the solutions to the LPs with linear constraints $A x = b$ and $A x = b + \Delta b$?

Let $x^*$ be the solution of the following LP: $$ \begin{array}{c l} \underset {x} {\mathrm{minimize}} & c^{\mathrm{T}} x\\ \mathrm{subject~to}~& A x = b. \end{array} $$ Let $\hat{x}^*$ be the solution of $$ \begin{array}{c l} \underset {x}…
Ryan
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Is it possible to get logical and with linear operations?

I'm currently trying to model a problem with GLPK. I am in a situation where I have two binary variables $a, b$ and I need a function $$f: \{0,1\}^2 \rightarrow \{0,1\}$$ such that $$f(0,0) := f(0,1) := f(1,0) := 0$$ and $$f(1,1) := 1$$ (So: $f =…
Martin Thoma
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Will the feasible region always be convex in linear programming?

In linear programming we find a feasible region , is this region always convex? . if a concave region is found where objective is minimization , I think then a solution exists . Advance thanks. someone deleted the answer of my previous post ,…
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Correctness of these linear programming formulations

Problem: A Company can use 3 different procedures to produce a product, for the production of every product are necessary 3 machines as below: The numbers relate the hours necessary. every machine is avaible for 50 hours. The profict of the…
abc
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What is the vector-diagram method of linear programming?

I am trying to find some information about the vector-diagram method of linear programming, but this seems that in my language this method has very different from English language name. So, I was wondering, maybe someone can recognize this…
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Do LP problems always have basic feasible solutions?

Assume that the feasible set is not empty. My textbook says if a basic solution satisfy nonnegative condition, then it is a basic feasible solution. I am wondering whether there are some theorems that can assure a LPP has at least one basic…
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Linear Programming question - Optimal solution

In Linear programming, you want to optimize stuff. For example; minimize the costs and maximize the profit. We have a series of constraints, in my case on either 2 or 3 variables. You can draw them in a coordinate system and you'll get a feasible…
Ylyk Coitus
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Showing a disc has infinitely many extreme points

EDIT: Stuck on a part of a problem for a Linear programming course. I want to show the unit disc is not a convex polytope and my strategy is to show that it has infinitely many extreme points. How would you show that every point along the boundary…
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Need help finding unknowns in simplex tableau.

I need help with this homework problem. The objective is to maximize $2x_1 - 4x_2$, and the slack variables are $x_3$ and $x_4$. The constraints are $\le$ type. Tableau $\begin{matrix}z & x_1 & x_2 & x_3 & x_4 & \text{RHS}\\ 1 & b & 1 & f & g &…
Daniel
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Why is the following not a a linear programming problem?

$$\begin{array}{ll} \text{maximize} & 3x + 3y − 30\\ \text{subject to} & |x−2|−|y| \leq 5\end{array}$$ This is totally a LLP to me, just not in its standard form. I really don't know why it is not? What I am missing? Thanks!
user533661
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How get the extreme directions of an unbounded feasible region

The following constraints form a feasible region. $-x_1+x_2 \le 2$ $-x_1+2x_2 \le 6$ $x_1,x_2 \ge 0$ The feasible region have three extreme points: $e_1=\left[\begin{array}{cc} 0\\ 0 \end{array}\right]$ $e_2=\left[\begin{array}{cc} 0\\ …
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Pivoting and Simplex Algorithm

I would like to understand exactly how the pivoting works geometrically in Simplex algorithm. What is meant geometrically by moving a vector into BFS and moving out one. Also, what is the geometrical implication of new variables introduced into the…
aghost
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Clarification about Simplex Algorithm concepts

We have the following generic program: $max \;\; c^Tx$ $\quad \quad Ax \le b$ $\quad \quad x \ge 0$ where $x$ is the vector of variables $(x_1, x_2,..., x_n)$. Suppose the origin is feasible. The it is certainly a vertex since it is the unique…
user137481
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Changes in the primal and dual that modify the solutions

Suppose we have in standard form an LP: $\max cx$ subject to $Ax = b$ and $x \geq 0$. Lets' write its dual as well \begin{align*} (P) \max cx &&&&&& (D) \min yb \\ Ax = b &&&&&& A^T y \geq c \\ x \geq 0 &&&&&& y \; \text{free}…