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:

5084 questions
0
votes
1 answer

Variable in Objective Function that not compares in inequalities

I am new to linear programming and I have learned that the objective function has the form: $$c^{T}x = c_{1}x_{1}+\cdots+c_{n}x_{n}.$$ And the equalities/inequalities that populate a Linear Programming Problem simply limit the domain of the…
Qwerto
  • 969
  • 6
  • 20
0
votes
1 answer

Writing linear program in standard form

Consider the problem $$ \begin{array}{ll} \underset {x_1, x_2, x_3} {\text{maximize}} & c_1 x_1 + c_2 x_2 + c_3 x_3 \\ \text{subject to} & x_1 + 2 x_2 + 3 x_3 \leq 6 \\ & x_1 \geq 0 \\ & x_2 \geq 0 \\ & 1 \geq x_3 \geq 0 \end{array} $$ Convert this…
0
votes
0 answers

Linear programming model for a retail online order

I'm reading up on Linear Programming and wanted to build a model for a scenario where there a set of N nodes should be found to be source for an order that has S set of items \begin{align} N_1, N_2, \ldots, N_n &\Rightarrow \text{ Nodes that hold…
0
votes
2 answers

Solving for maximum value

I have $x\ge983614$, $y\ge268877$ and $z\ge514175$. Also I am told that the sum of $x+y+z$ can not be greater than $3500000$. I am requested to find the values of $x,y,z$ such that $\max f(x,y,z) = 117x+125y+97z$. In other words, I need to find the…
0
votes
1 answer

Using Farkas' lemma to indicate infeasibility of a linear programming problem

In the article "How to use Farkas' lemma to say something important about linear infeasible problems by Prof. Andersen, E.D. (link cited below), he wrote about how we can use Farkas' lemma as a certificate for the infeasibility of a linear…
ElementX
  • 922
0
votes
0 answers

Taking the dual of this two-dimensional linear program

I have just begun learning about LP duality and how to take the dual of an LP, however this question I've come across has me stumped: \begin{alignat}{4} \max \quad & \rlap{\sum_{j=1}^{m} \sum_{i=1}^{n}v_{ij}x_{ij}} \\ \text{s.t. } \quad &…
0
votes
1 answer

Confusing Linear Programming Problem

In a linear programming problem, I encountered a situation where the maximum value of independent variables are fraction at an angular point [Variables are such that the can't be fraction].Then my teacher told me to find the values of variables in…
user524745
0
votes
2 answers

Find minimal value of function with 3 variables (Linear Programming)

Minimize 2x + 2y - z Subject to x + y + z = 10 x,y,z >= 0 Okay so the answer to the problem is clearly -10 with x=0, y=0 and z=10 that's just common sense. But unfortunately I've got to show some reasoning. Can anybody show me what I'm supposed…
0
votes
1 answer

How to add nonnegative constraint to an LP problem

I have the following LP problem (from Bazaraa, Jarvis and Sherali Linear Programming and Network Flow problem 1.30): Minimize $x_1 - 2x_2 + 3x_3$ s.t. $-x_1+3x_2+x_3 \le13$ $ x_1+2x_2+3x_3 \ge 12 $ $2x_1-x_2+x_3 = 4$ $x_3 \le -3$ I need to convert…
0
votes
1 answer

Select the smallest strict positive value from a list of variables in a linear program.

I have constraints set up for my Linear Program. The constraints enforce a certain amount of decision variables $R_{w,h}$ to be either $0$ or $1$ (0-1 variable). The value to minimise is the difference between the largest and smallest $w*h$ for…
Auberon
  • 459
0
votes
1 answer

Is there any way to model this situation in integer programming?

I have a binary variable $z_{ij}$. Some constraints are given by: $$a_j\geq b_i z_{ij},$$ where $a_j$ and $b_i$ are given nonnegative inputs BUT $a_j$ changes depending on the solution $z_{ij}$. I mean, initially (before solving the problem), I…
zdm87
  • 99
0
votes
1 answer

Basic primal and dual solution. Feasible? Why?

Questions Attempt I managed to solve (c) but I have trouble understanding (d) any directions would be incredibly useful.
0
votes
2 answers

Transportation problem in linear programming with a twist

I've been trying to solve a close to the classic transportation problem, but with a twist. The twist is that the transportation from say factory A to supermarket 1 is being done in trucks. So no matter if I transport 1 tonne or 9 tonnes from A to 1…
mm8ss3
  • 1
0
votes
1 answer

detecting hidden equality constraints in optimization

I have a system of linear inequalities $Ax \leq b$. It is possible that some inequality constraints actually create a linear equality constraint. for e.g. $ax \leq b$ and $ax \geq b$ implies $ax=b$. A more involved linear combination of inequalities…
0
votes
1 answer

Two phase and redundancy

[4.7] Phase I of the two-phase method can be made use of to check redundancy. Suppose that we have the following three constraints: X1 - 2x2 > 2 X1 + 3x2 > 4 2X1 + x2 > 6 Note that the third constraint can be obtained by adding the first two…