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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Explicitly solving linear programming problems

Linear programming problems generically involve the use of a repeated algorithm to solve. Is there a reason they can't be solved algebraically/formulaically? Ex: Minimize x1 + x2 + x3.... x1, x2, x3... >= 1 Has a solution (1,1,1...) for any…
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Simplex Method row operations help?

before programming an algorithm which implements the simplex method, I thought I'd solve an issue before the actual programming work begins. For some reason, I can NEVER get the correct answer. I've understood the method, but the problem is with the…
simplex
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Can this dual LP be solved?

The primal problem is as follows: $\min w=2x+4y+5z+3q$ subject to $$ \begin{split} -x - 2y + 2z &\geq 40\\ -3x - 2z - q &\geq -100\\ x - 2y - z + 4q &\geq 50 \end{split} $$ I have transformed it into dual LP and obtained: $\max…
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Show that two Linear Programming problems are equal

Consider the general linear programming problem $min \sum_{j=1}^n c_jx_j$ s.t. $\sum_{j=1}^n a_{ij}x_j \leq b_i$, for $i=1,\dots , m$ $x_j \geq 0$ for $j=1,\dots , n$ And the corresponding extended formulation $min \sum_{j=1}^n c_jx_j$ s.t.…
dreamer
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Multiple variable optimization methods with constraints

This is something I'm doing for a video game so may see some nonsense in the examples I provide. Here's the problem: I want to get a specific amount minerals, to get this minerals I need to refine ore. There are various kinds of ore, and each of…
Juan Fuentes
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Extreme points and basic feasible solutions

Suppose we are given a polyhedron $P = \{x\in\mathbb{R}^n | Ax = b, x\geq 0\}$, where $A\in\mathbb{R}^{m\times n}$ has linearly independent rows. I want to show that an extreme point of this polyhedron is a basic feasible solution to the associated…
t42d
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Simulation of a General equation

I have solved a programming problem with a Equation. But can't simulate this equation briefly. Anyone can help me? Question: I have $n$ rubles initially. The cost of one plastic litre bottle, the cost of one glass litre bottle, and the money one can…
aspile
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A condition for an LP to be unbounded

Let $(P)$ be an LP of the form $$min \ c^tx \text{ with } Ax \le b,x \ge 0.$$ Show that if there is a vector $d$ such that $Ad=0,d \ge 0$ and $c^td<0$ $(P)$ is unbounded . Could you help me?
3nondatur
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Why can't the dual and primal linear program both be unbounded?

I know if a dual is unbounded then the primal is unfeasible and vice versa, but I don't know why they can't both be unbounded. Is it because it's impossible to have linear constraints that are unbounded in the direction of the gradient and the…
Gooby
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Finding an optimal solution to a linear program among solutions of another

I had the following question on my last Algorithms test which I didn't know how to solve, and the the professor didn't agree to publish the solution. I would like to know the solution though, since it's been bothering me not knowing. I am given two…
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Structure of an Optimal Solution to a Fractional Packing Problem

Packing LP We have the following optimization problem: $$ \max_{x_{ij}} x_{ij} c_{ij}$$ s.t. $$(i)\forall j\mbox{ }\sum_{i} x_{ij} \leq \beta_j$$ $$(ii)\forall i\mbox{ }\sum_{j} x_{ij} D_{ij} \leq 1$$ $$(iii)\forall i\mbox{ }\forall j\mbox{ }0 \leq …
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Linear Programming and graphing (Mathematics in thw Modern World)

I need help with the #1 question. linear Programming is applied. 1. Consider the recipes below: Pancakes -Waffles 3 cups Bisquick 3 cups Bisquick 1 cup Milk. 2 cups Milk 2…
Be ar
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How do I find the Dual of the LP

min $ = 4y_1 +2y_2 - y_3 $ $s.t. y_1 + 2y_2 +2y_3 <= 6$ $s.t. y_1- y_2 + 2y_3 = 8$ $y_1, y_2 >= 0, y_3 $urs How do I find the dual to this LP? What confuses me is the = sign. Also the urs variable. I'm not sure how to act on these.
user634512
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What exactly is a basis matrix in LPP?

I'm studying simplex for solving a LPP. $A$ is a $m\times n$ matix. $$Ax=b$$Then the book says: Let $x$ be a basic feasible solution to the standard form problem. Let $$B(1), B(2),\cdots B(m)$$ be the indices of the basic variables and let…
Ankit Kumar
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Could I have two optimal solutions - linear programming problem?

A company produces two different products. They require two types of ingredients: M and N. The first product require 90 grams of the ingredient M and 10 grams of the ingredient N. The second product require 20 grams of both ingredients. The company…
bdvg2302
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