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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Express the feasible solution (3,1) as a convex combination of extreme points

So i am given four extreme points: $A: (0,0)$ $B: (8,0)$ $C: (2,3)$ $D: (0,1)$ and I need to express the feasible solution $(3,1)$ as a convex combination of extreme points. My professor did the following, he expressed it…
mika
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Optimal basis in linear programming

Given the following linear program: \begin{cases} \max &5x_1 + x_2 + 6x_3 + 2x_4\\ &4x_1 + 4x_2 + 4 x_3 + x_4\le 24\\ &8x_1 + 6x_2 + 4x_3 + 3x_4\le 36\\ &\forall i, x_i\ge 0 \end{cases} How to know if the basis $B=\{3,4\}$ is an optimal basis? I…
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Mathematical Programming Community

Is there a good online community for discussing optimization models? The ones I have found don't seem to have a critical mass for active discussions.
Bob
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Big M formulation of an indicator constraint.

This is my first question here. I am working on a binary LP wherein I want to turn on a variable when a condition is met else make it zero. I want to share my formulation with you and need your help in understanding whether my constraint gets the…
crypto
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Ex. 1.11 in "Linear Optimization" by Bertsimas, Tsitsiklis

I'm trying to follow the syllabus of 6-251j at MIT OCW and need to understand whether I'm doing fine with the exercises. This is what Ex. 1.11 says: Suppose that there are $N$ available currencies, and assume that one unit of currency $i$ can be…
Alexey B.
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Simplex algorithm in linear programming...

I've just had a lecture in which the simplex method was described and solved graphically (not using the tableau method I've seen after a quick Google). The professor would give us examples and we'd identify the function to maximize/minimize and then…
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Why do the decision variables in a linear optimization problem have to be non-negative?

Why do the decision variables in a linear optimization problem have to be non-negative? I mean it makes sense in certain scenarios (when you are talking about how many pairs of two shoes to make for maximum profit) as you can't make negative shoes…
Chris K
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How can I determine feasability / optimality given a set of variables?

I have a linear programming problem that already has the slack variables defined and is in convenient matrix form. There are no artificial variables. I've been told that $x_1$ and $x_3$ are basic variables, and I've been asked to determine whether…
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Tutorial for Simplex Method with No Slack Variables

I found a nice tutorial here http://www.math.ucla.edu/~tom/LP.pdf for applying the Simplex Method to problems of the form: maximize $c^T x$ with the constraints $Ax\leq b$, $x_i \geq 0$. It suggests introducing "slack variables" to convert it to the…
Izzhov
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Linear Programming 3 decision variables (past exam paper question)

This is an exam question I was practising. I have the general understanding of Linear programming, but how would you go about finding the Decision Variables, Objective function and Constraints for this? My Opinions: Decision variables: $M_1$- # of…
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Finding number of basic solution based on different cases

I need help understanding the question. Consider the polyhedron P = {x in R^n | Ax = b x => 0}, where A in R^mxn and b in R^m. Assume that any m columns of A are linearly independent. (a) Suppose all the basic solutions are nondegenerate. Express…
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primal to dual conversion problem

primal problem is: $$\min z = 4x_1-3x_2+5x_3$$ $$7x_1+6x_2+24x_3\le16$$ $$2x_1+5z_2+3x_3\le10$$ $$x_i\ge0$$ the optimal solution is: $(0,2,0), z = -6$ The dual problem is : $$ \max g =…
kabal
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How to maximize the sum of vectors in target direction.

Given a number of vectors, and an unknown variable for each vector, say for example: $v_1, v_2, v_3,\dots,v_n$ and $x_1, x_2, x_3,\dots,x_n$ and a target vector $v_t$ I am trying to create an algorithm to maximize $p$ by setting $x_1, x_2, x_3,…
Patrick
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Need help with a Linear Programming homework.

Please help with the problem: A polyhedron P in $R^n$ is given by the system of m linear inequalities (of n variables). Furthermore, let P have k vertices (that is, k vectors satisfying all m constraints at least for n of which the equalities…
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how Determine the maximum values of C.

how Determine the maximum values of C. my try is that : To graph the last two bounding lines, I'll want to put the equations into slope–intercept form. The bounding line corresponding to the 3rd constraint inequality becomes: 2y = 8 + 4x y = 4 +…
user155971
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