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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Computing initial feasible basis in the simplex algorithm

My textbook introduces the following method to compute initial feasible basis in the simplex algorithm: What is the implication for the original LP if the auxiliary LP's objective function can't attain the value $0$, or if it is infeasible?
ensbana
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Transforming a linear program into its canonical form for use in the simplex algorithm

A typical example of a LP in my lectures looks like this: From what I've learnt, we are ready to implement the simplex algorithm on this LP, since $x_3, x_4, x_5$ all have positive signs, and so are the right hand sides of the constraints. Now I…
ensbana
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Facility Location Problem with Integer Linear Programming

I am trying to create a linear programming formulation based on a facility location problem. In this problem, it is the goal to minimize the costs of travelling from 50 customers to 3 facilities. These have yet to be built and there are 20 possible…
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LP: New way of minimizing sum of absolute values

Original Optimization: Let say I want to minimize below function: minimize $\left|a_1x_1+a_2x_2-c_1\right| + \left|b_1x_1+b_2x_2-c_2\right|$ subject to: $x_1^{lower} \le x_1 \le x_1^{upper}$ $x_2^{lower} \le x_2 \le x_2^{upper}$ Solutions…
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How to prove a specific linear programming problem has exactly one solution

I have the linear programming problem as follows maximise $f(x,y)=5x+2y$ subject to $x+3y \le 14$, $2x+y \le 8$, $x,y \ge 0$ If you solve this graphically then you can see a feasibility region with four extreme points, of which one of…
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How to find an optimal solution of the dual from the primal tableau?

The tableau above is an optimal tableau of a LP problem. If I want to find the optimal solution of dual, I know, I can rewrite this in terms of the original problem and remove the slack variables $x_4,x_5$ and then find the dual which is 2…
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Linear programming, artificial and slack variable, the difference

I have a metaquestion: what is the difference between the slack and artificial variable in the standard LP problem?
user122424
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an artificial vector in the big M method that produces a BFS

Suppose we have LP maximization where the constraint are put in the form $I {\bf x_B} + B^{-1} N {\bf x_N} = {\bf \overline{b} } $ where : ${\bf \overline{b }} \ngeq 0 $ If we add just one artificial variable, say $s$ with activity vector ${\bf…
James
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Understanding the tableau form of the simplex algorithm in LP

Given the following tableau for a max LP \begin{array}{|c|c|c|c|} \hline & \text{z} & x_1 & x_2 & x_3 & x_4 & x_5 & x_6 & \text{RHS} \\ \hline \text{z} & 1 & c_1 & 0 & c_3 & 0 & 0 & 0 & 13\\ \hline x_2 & 0 & -4 & 1 & a_1 & 0 & a_2 & 0 & \text{b}\\…
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Linear programming with many constraints and few unknown variables

Vectors $x, y \in \mathbb{R}^{n\times 1}$ satisfy $$ \forall_{i,j}\; x_i + y_j \leq a_{i,j} $$ where $a\in \mathbb{R}^{n\times n}$ is a given matrix. The question is to find the maximum value of $\sum_i x_i + \sum_j y_j$. My idea Suppose $t$ is a…
useprxf
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Show that the set of all feasible solution of a linear programming problem is a convex set.

How to show that the set of all feasible solution of a linear programming problem is a convex set theoretically.
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Degenerate feasible basic solution

In Linear programming a degenerate basic feasible solution leads to no increment of the objective function. How , intuitively, the fact that a degenerate solution has at least one variable = 0, it's connected with the fact that it leads to no…
Qwerto
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Multiple optimal solutions for a linear programming problem

I'm attempting the following problem: $\max\ \ 6x_1 + 5x_2 + 4x_3 + 5x_4 + 6x_5\ \ $,$\ \ $subject to $x_1 + x_2 + x_3 + x_4 + x_5 \leq 3,$ $5x_1 + 4x_2 + 3x_3 + 2x_4 + x_5 \leq 14,$ $x_i \geq 0\ \ $ for all $i$. I'm supposed to formulate the dual…
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Solving a dual linear program using complementary slackness if primal constraints are tight

I have a doubt in the following question: Consider the linear program $\min\ \ 5x_1+12x_2 + 4x_3\ \ $, $\ \ $subject to $x_1+2x_2+x_3 = 10$ $2x_1-x_2+3x_3=8$ $x_1,x_2,x_3 \geq 0$ You are given the information that $x_2$ and $x_3$ are positive in…
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Fit a boolean condition into the framework of Linear Programming

$a=k.B$, where $a$, $B$ (binary), $k$ all are scaler variables. When $B=0$, $a=0$; and when $B=1$, $a=k$. $B$ is binary, i.e., $0$ or $1$. $k$ is $0$ or positive integer, i.e., $0, 1, 2, 3, 4...$ How to decompose it in Linear Programming so that…
Dr.PB
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