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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Need some help implementing a linear program with a parameter and deviational variables for quantile regression areal interpolation

I'm trying to implement an areal interpolation technique described in https://www.tandfonline.com/doi/abs/10.1080/00045608.2011.627054 but I'm struggling to understand how the linear programming formulation in the paper translates to something like…
Dan Evans
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binary variable question

I need to make a constraint for the following condition: Student 1 can only be on the team if students 2, 3, 4, and 5 are also on the team. I'm not sure how to model this using equations. The equations must not have "and", "or", or "not equal to"…
icobes
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Gomory cut for knapsack problem

Knapsack problem: Maximize $24 x_1 + 2 x_2 + 20 x_3 + 4 x_4$ subject to $8 x_1+ 1 x_2+ 5 x_3+ 4 x_4 ≤ 9$ $x$ is binary for $i = 1,2,3,4$ How can I find a gomory cut for this problem? I think that $x_1 + x_3 \le 2$ would be a gomory cut, but I am…
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Proving the existence of a solution to a self dual problem

I'm working on the following exercise: Let $a \in \mathbb{R}^{n \times n}$ be a skew symmetric matrix and $ b \in \mathbb{R}^n$ with $c = -b$. Consider the following $(LP)$ named $(P)$ $$\min_{x \in \mathbb{R}^n} c^Tx$$ $$ \text{such that: } Ax \ge…
3nondatur
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linear programming primal and dual programs variable without constraint

I have a task to write a dual program for the following primal: maximize $x_1 + 2x_2 + 3x_4$ subject to $x_2 - 6x_3 + x_4 \leq 4 $ $x_1 + 3x_2 - 3x_3 = 0$ $6x_1 - 2x_2 + 2x_3 - 4x_4 \geq 5$ $x_2 \leq 0$, $x_4 \geq 0$ However, $x_1$ and $x_3$…
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Linear Programming: The costvector can be expressed via the active restrictions

I' trying to solve the following problem: Consider the problem $$min_{x \in \mathbb{R}^2} c^Tx$$ $$\text{such that: }$$ $$Ax \ge b$$ for $$A = \begin{bmatrix}1 & 1\\1 & -1\\-4 & 1\end{bmatrix}, b=\begin{bmatrix}2\\-2\\-4\end{bmatrix},…
3nondatur
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Find the values of $ \ a,b \ $ so that the polyhedral set has extreme direction

Find the values of $ \ a,b \ $ so that the polyhedral set defined by the system of inequalities $$ ax+(b+1)y \leq 120 \\ x+(a+b)y \leq 160 \\ (a-b)x+y \leq 30 \\ x \geq 0 \\ y \geq 0 $$ has extreme direction. Answer: Does extreme direction means…
MAS
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A cross examination problem in convex program

I have four variables $a,b,c,d$ and I want to know either $a=c$ and $b=d$ holds or $a=d$ and $b=c$ holds or both do not hold. I want to set $t=1$ if either condition holds. Else I want $t=0$. Is there any way to check which condition holds in convex…
Turbo
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Why can one assume without loss of generality that the constraint $\mathbf{b}$ in linear programs is non-negative?

Problem 9.16 of The Nature of Computation states Jumpstart for LP. How do we find an initial feasible solution for the simplex algorithm? By solving another linear program for which we know a feasible solution! As we outlined in Section 9.4.1, we…
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Standard Form linear programming

What are the advantages of using the Standard Form in Linear Programming, over the general form of a linear programming problem ?
Qwerto
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Linear programming optimal solution

I am sitting with a problem, which has been confusing me. I have a primal problem, then I find the dual one. Afterwards I am asked to find the optimal solution of the Dual problem and then show that it is the optimal solution. I have not been able…
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Simplex Method: What pivot element, as none fullfill criteria?

I transformed the linear programming problem, where $x_1$ and $x_2$ also has to be non-negative: $$ \begin{array}{rrrrrrrl} (P) & \text{min. } & \xi & = & x_1 & + & 3x_2 &\\ & \text{st. } & -x_1 & & &\geq & -2.5\\ & & …
Frederik
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Conversion of Standard Linear Programming

Convert the standard Linear Programming where $\mathbf{A}\in\mathbb{R}^{m\times n} $ and $x\in\mathbb{R}^n$ $$\min \mathbf{c}^T\mathbf{x}\\ s.t\;\;\;\;\;\;\;\mathbf{Ax}=\mathbf{b}\\ \;\;\;\;\;\;\;\;\;\;\mathbf{x}\geq 0 $$ The question wants to…
user122049
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Duality - How is g defined?

I am studying on linear programming and there is just something that I dont get. For the linear program $ \min \ c^Tx \\ \text{s.t.} \ \ Ax \le b $ Its lagrange is defined as $L(x, \lambda) = c^Tx + \lambda^T(Ax-b)$ The dual function is then…
Kong
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Question regarding duality in linear programming

I have the question regarding the expression of the dual formulation of a linear program. I think it is very simple but I just dont get (1) below $ \min \ c^Tx \\ \text{s.t.} \ \ Ax \le b $ $L(x,\lambda) = c^Tx + \lambda(Ax-b)$ $g(\lambda) = \inf_x…
Kong
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