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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Linear Programming 3 decision variables (past exam paper question)

This is an exam question I was practising. I have the general understanding of Linear programming, but how would you go about finding the Decision Variables, Objective function and Constraints for this? My Opinions: Decision variables: $M_1$- # of…
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Question about LP Model

I have a aggregate production planning problem. As the company want to have a stable output, the quantities produced per month should (x) not fluctuate to heavily from a specified amount, say g. So now I want to add a cost factor to my cost…
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Turning the program with absolute terms into the linear program

I am studying the linear programming and stuck with the following two problems. I don't have any clues how to convert programs with absolute terms into a linear program. I highly appreciate your help. $min f(x)= 5 \lvert x-3\rvert + 2 \lvert…
N1227
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checking optimality using complementary slackness

I am trying to see if [3,-1,0,2] is an optimal solution to the following LP using complementary slackness: maximize $6x_1 + x_2 -x_3 - x_4 $ s.t. $x_1 + 2x_2 + x_3 + x_4 \leq 5 $ $3x_1 + x_2 -x_3 \leq 8 $ $x_2 + x_3 + x_4 = 1 ,$ $x_3, x_4 \geq 0…
user55531
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linear programming 'increasing profit'

Consider, $$\max 1.000.000x_1 + 2.500.000x_2 $$ \begin{align} s.t. x_1 + 2x_2 \le 7 \\ x_1 + 3x_2 \le 10 \\ -3x_1 + x_2 \le 0 \\ x_1, x_2 \ge 0\end{align} which is an LP-problem on a company's wishes to maximise profit given certain constraints on…
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finding the dual

I am supposed to find the dual of max $c^Tx$ subject to $a \le Ax \le b$ $l \le x \le u$. In order to find the dual I think I have to write it in standard form, the standard form is: max $Ax'$ subject to: $A'x'\le b'$ $x' \ge 0$. The way I try to…
user119615
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Linear optimization problem with additional constant cost for non-zero variables

I have a linear optimization problem with integer variables of the form minimize $a_1 x_1 + ... + a_n x_n$ under a set of constraints Bounds for each variable $a_i \le constant_i$ Bounds for groups $ a_{j1} + ... + a_{jk} \le constant_j$ Which R…
Beginner
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How is the pivot chosen for the symbolic weights for the Cassowary algorithm?

I am trying to understand The Cassowary Linear Arithmetic Constraint Solving Algorithm, and I am having trouble understanding symbolic weights, starting in section 2.3. Working through the example, this is the objective…
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Casting a linear (in)equality into a linear program problem

Suppose I have the systems $$S_1: Ax \leq b$$ where $A \in \mathbb{R}^{n\times m}$, $x \in \mathbb{R}^m$ and $b \in \mathbb{R}^n$, and $$S_2 : y^{\intercal}A=0,\\ y \geq 0,\\ y^{\intercal}b < 0 $$ where $y \in \mathbb{R}^n$. I want to cast these…
Stijn
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duality theory question

Let $A$ be a given $m$ x $n$ matrix, and $c\in R^n$ and $b\in R^m$ be given vectors. Use LP duality theory to show that if the problem $$\min\{x^Tx: Ax=b, x\geq0\}$$ has a finite optimal solution, then the following problem $$\min\{c^Tx: Ax=u, x\geq…
snowman
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Solving LP from tableau

$$\begin{array}{cccccc} & x1 & x2 & x3 & x4& x5 \\ -4& 2 & 0& -2 & 0& 3\\ 3 & 1 & 0 & -1& 1 & 3\\ 2 &0& 1 & 0& 0.5 & 2\\ \end{array}$$ When I learned about solving LP represented by the tableau in…
John
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Reverse Linear Programming Formulation

My question is about having an LP in the standard form $Ax \leq b$ and the set of basic feasible solutions. For each basic feasible solution (bfs) does there exist an appropriate objective function $cx,$ such that this bfs is the optimal solution…
koh
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Why does the simplexmethod 'break up' - unbounded, LP program, very basic problem

I've calculated a very, very basic LP problem: with >= "greater or alike" and <= "smaller or alike" max x + 2y 4x + 3y >= 12 x <= 4 With ORSTAT (LP program) this turned out to be "Unbounded",…
Robin
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linear programming problem given initial solution

While dealing with a linear programming problem we usually try to start with the basic feasible solution corresponding to the identity Matrix in the coefficient matrix. I have no idea how to solve the following type of LPP: Solve the LPP using…
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LP model constraint formulation

We have a production plant that for each ton of $a$ requires $p_x$ tons of $x$ and $p_y$ tons of $y$ and we must decide how much material to ship to this plant. Is it just $a = y/p_y = x/p_x$? Do I need more constraints?