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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Two forms of duality in linear programming

I do not know much about this subject, but I am trying to learn a little. In a book I have it says that a primal problem is: max $c'X$ subject to $AX \ge b$ $X \ge 0$ It says that the dual of this is: maximize $b'Y$ subject to: $A'y \le c$ $Y…
user119615
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Assigning jobs to minimize cost - Linear programming

I'm stuck trying to solve this linear programming question. You want to make a website with a list of features F, which are n elements long. Each feature has a corresponding value for how long it'll take to implement it. Since you dont know how to…
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Prove feasible direction

If $x$ is an element in a standard convex linear optimization set constrained by $Ax = b, x \geq 0$, then how can I prove $d$ is a feasible direction only if $Ad=0$ and $di \geq 0$ for every $i$ where $xi=0$?
GBa
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How to show two linear programs are equivalent?

We know that 1-norm is defined as $\|v \|_1 = |v_{1}| + \dots + |v_{n}|$ for the vector $v = \left(v_1, \dots, v_n\right)^T$. Suppose we have program (a) $$ \min\limits_{x} \|Ax-b\|_1 $$ and program (b) $$ \min\limits_{u,x}…
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finding the minimum number of lines to cover all zeros in an assignment problem

I have been trying to follow the following steps to find the minimum number of horizontal and vertical lines that cover all the zeros in an assignment problem using Hungarian method: Tick all unassigned rows. If the ticked row has zeros, then tick…
johny
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Finding dual of linear programming problem

I have to find the dual to this linear programming problem: Maximize $-15z-\frac{11}{20}w-3a-3b=-132+p$ subject to $y+9z+\frac{13}{10}w+3a-2b=12$ $x-2z-\frac{7}{20}-a+b=4$ $14z-\frac{69}{20}w+7a-7b+c=42$ I tried looking it up online, but the…
Alti
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travelling salesman understanding constraints

I am trying to program TSP problem in R. From wikipedia page section "Integer linear programming formulation", I was able to understand all the constraints except the last one. Need help to understand the last constraint...what are the variable…
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Binary constraint integer programming problem

I have a question to the folowing question: Explain how to use integer variables and linear inequality constraints to ensure: A) let $x$ and $y$ be integer variables bounded at 1000. How can you ensure that whenever $x\leq 2$ we have $y\leq 3$.…
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Whether a feasible set is empty?

Given $a\in \mathbb{R}^N$ with at least one positive entry, and a positive definite $N\times N$ matrix $A$, I would like to prove the following set is non-empty: $$S=\{ x\in \mathbb{R}^N : x\geq 0, Ax\geq a\}$$
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How does the dual solution change when multiplying the objective function of the primal with a constant?

Suppose we have the problem min $c^Tx$, subject to $Ax = b, x\geq 0$. The dual is then max $b^Ty$, subject to $A^T y \leq c$. We assume that the linear and dual program are feasible and bounded. Let $y^*$ denote the optimal solution of the dual…
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Formulating a linear programming problem

I have the following problem: Now I would like someone to verify whether my answer is correct or not :) Here goes: If I denote the different alloys by $x_1, x_2, x_3, x_4, x_5$ I get $$\text{minimize}\;\;\;5x_1+4x_2+3x_3+2x_4+…
jjepsuomi
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Converting linear programming problems into standard form

I have the following linear programming problem: Convert the following problems to standard form: $$\begin{align} \text{a)}&\text{minimize}&x+2y+3z\\ & \text{subject to}&2\le x+y\le 3\\ & &4\le x+z \le 5\\ & &x\ge 0,…
jjepsuomi
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How to determine if a constraint is redundant in a linear programming problem

my TA told me that a constraint is redundant iff it is a linear combination of the other constraints. Let's consider these constraints: $2x_1 + x_2 \leq 4$ $-2x_1 + x_2 \leq 2$ $x_1 - x_2 \leq 1$ Also $x_1,x_2 \geq 0$ If we draw a graph, we'll see…
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Find a feasible but not optimal solution to a large LP

I have a large linear program, which I need to solve fast. I'm willing to sacrifice optimality but not feasibility. I have an initial feasible point x0. Any suggestions for an algorithm? For example, I could use the simplex algorithm (using my x0 as…
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How to say that $x+y \in \{5,7,11,17,22 \}$ in linear programming language?

Title says it all. I considered the use of the big-M method for inequalities, where out of $N$ constraints, if you want to choose one of the form $f_i(x) \leq 0$ you do $f_i(x) \leq M_i (1-\delta_i)$, where $M_i$ is large enough so there are no…