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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Shadow prices in linear programming

I am quite confused about the meaning of shadow price from explanations on the internet. It can be understood as the value of a change in revenue if the constraint is relaxed, or how much you would be willing to pay for an additional resource. For…
spflee
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How can not-equals be expressed as an inequality for a linear programming model

I have this linear programming model I'm building but one of the constraints needs to specify that the solution's basic variables need to all be different from one another. This is an integer linear program. How can we rewrite, for example, this…
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Primal and dual solution to linear programming

Lets say we are given a primal linear programming problem: $\begin{array}{ccc} \text{minimize } & c^{T}x & &\\ \text{subject to: } & Ax & \ge & b \\ & x & \ge & 0 \end{array}$ The dual problem is defined as: $\begin{array}{ccc} \text{maximize…
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Linear programming: Maximize minimum of linear functions

For a project I need something solved, it screams linear programming. If I get the problem in "standard" form I should be able to solve it using the simplex method. But I don't see how to get it in standard form. The problem is this: Maximize…
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Construct a linear programming problem for which both the primal and the dual problem has no feasible solution

Construct (that is, find its coefficients) a linear programming problem with at most two variables and two restrictions, for which both the primal and the dual problem has no feasible solution. For a linear programming problem to have no feasible…
dreamer
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Basic and non basic variables in linear programming

I dont understand what are Basic and non basic variables,why we are talking them specially, what they have got to do with the rank of the coefficient matrix and augmented matrix ,and some deal with the linearly independent set corresponding to the…
BAYMAX
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linear programming set a variable the max between two another variables

i'm having problems with this. Suppose i have two real variables, A and B, and another one C. I want to store the max between A and B in C for a problem im modeling. I can't use a max function, neither multiply variables. What can I do?
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Computationally proving a linear programming solution is unique?

I have a simple linear programming problem min $c^{T}x$ subject to $Ax\leq b$. That gives me the solution I am looking for when solving in maple. My only problem is that I do not know how to check, with maple, whether or not this solution is unique.…
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How does multiplying a primal constraint by a constant change the dual solution?

Suppose we have the problem $\min c^T x$, subject to $Ax=b, x \geq 0$. Suppose that this program and its dual are feasible. Let $\lambda$ be the optimal solution of the dual. If the $k$th constraint equation of the primal is multiplied by $\mu \neq…
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Linear programming problem formulation

Stuck in this problem for quite a while. Anyone can offer some help? The problem is as follows: Fred has $5000 to invest over the next five years. At the beginning of each year he can invest money in one- or two-year time deposits. The bank pays 4%…
zf xiao
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Prove a variant of Farkas' Lemma

Farkas' Lemma is given as follows Let $\pmb A\in\mathbb R^{m\times n}$ and $\pmb b\in\mathbb R^m$. Then exactly one of the following two assertions is true: 1.1. There exists an $\pmb x\in\mathbb R^n$ such that $\pmb A\pmb x=\pmb b$ and $\pmb x\ge…
Maybe
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Understanding proof of Farkas Lemma

I've attached an image of my book (Theorem 4.4.1 is at the bottom of the image). I need help understanding what this book is saying. In the first sentence on p.113: "If (I) holds, then the primal is feasible, and its optimal objective is …
Matt Gregory
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Are all linear programs convex?

A linear program is given as follows: $$\min_{Ax \le b} \{c^T x\}$$ where A is a $ n\times n $ matrix Is this always a convex optimization problem or does it depend on c?
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Simplex method : Duality by Bazaraa

I use a great textbook (Linear Programming and Network Flows by Bazaraa II ed) On page $240$ the author states that for every primal problem, regardless of its type (canonical or standard), a dual problem can be found by using the following…
com
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Get reduced costs from simplex tableau

This is probably a dumb question... but I'm trying to find how to calculate the reduced cost for a particular variable based on the information in a simplex tableau after I've minimized a linear programming problem. I've been googling like crazy…
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