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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Trying to Determine if an Optimal Solution from an LP Solver is Indeed Optimal

Suppose we have the following LP problem: $$min\ C^Tx $$ $$s.t. \ Ax = b $$ $$x>=0$$ I am trying to confirm that an optimal solution $x^*$ obtained from an LP solver for such a problem is optimal. To do so, I am calculating the reduced cost and…
Maad
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True or false questions for LP and the simplex method

True or false? (a) Deleting a constraint leaves the feasible region larger. (b) Adding a constraint leaves the feasible region either unchanged or smaller. (c) An LP cannot have an unbounded objective function value. Here are my answers: (a) True…
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The linear program for widest path or maximum capacity path problem.

I have to give the linear program for the widest path problem or maximum capacity path problem which gives the path where the greatest flow is achieved. I thought of solving it as a Max Min problem. First to find all edges that have the minimum…
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Transportation problem in linear programming

It is given the following transportation problem. I can solve it when the cost is increased, but I don't understand what is the change in the model when the transport cost is reduced. Problem: It is required to move machines from factories $A, B$…
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How to linearize logical AND constraint in linear programming?

I want to implement " if($x_{i,k}=1$ AND $x_{j,k}=1$) then $p[j]\geq p[i]$ " as a linear constraint. Where $x_{i,k}$, $x_{j,k}$ are binary decision variables and p[i], p[j] are integer decision variables. I know that we can implement if-then…
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Where do the points (-1,3) and (2,1) come from?

I now understand how the green area is obtained from the set definition below in point 2, but how is that set itself constructed? More precisely, where do the points $(-1,3)$ and $(2,1)$ come from?
Parseval
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Draw region given set of points.

Can someone explain how $$\{\mathbf{x}\in\mathbb{R}^2 \ | \ \mathbf{x}=\begin{pmatrix}2\\2\end{pmatrix} + \lambda_1\begin{pmatrix}-1\\3\end{pmatrix}+\lambda_2\begin{pmatrix}2\\1\end{pmatrix};\lambda_1,\lambda_2>0\}$$ is the green area below?
Parseval
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Linear Programing For Forest Management

The question I am working on is as follows, You are in charge of managing a $200,000$-acre forest. Of these $200,000$ acres, $80,000$ can only grow pine and $40,000$ can only grow aspen. The remaining $80,000$ acres can grow either pine or aspen,…
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linear programming - variable satisfies non-zero lowerbound or zero

I have a linear programming problem of the form $\max_{x_1,\ldots,x_N} \mathbf{c}^T\mathbf{x}$ such that $\mathbf{Ax}\leq \mathbf{b}$ and ($x_{\text{min}}\leq x_i\leq x_{\text{max}}$ or $x_i=0$) where $x_{\text{max}}, x_{\text{min}} > 0$ So the…
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What does it mean when we can't put a particular variable as a basic variable in a LPP?

Consider the LPP of minimizing $z = -2x_1 + x_2$ subject to $$\begin{cases} x_1 + 2x_2 \le 6, \\ 3x_1 + 2x_2 \le 12, \\ x_1, x_2 \ge 0 \end{cases}$$ First I add slack variables $x_3, x_4$ which immediately puts the problem in canonical…
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Linear programming problem minimization change problem

minimize $max ${x1,x2} subject to $2x1+5x2<=9$ $x1+3x2<=5$ $x1>=0$, $x2>=0$ show that both are same and give reason minimize t subject to t>=x1 , t>=x2 $2x1+5x2<=9$ $x1+3x2<=5$ x1>=0, x2>=0 i tried let t>=max{x1,x2} then t>=x1 and t>=x2 am i right?…
vedss
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Linear programming with what I think has 3 variable. I need to plot a graph of the constraints too.

I have a question. A refinery gets oil from three wells. Each wells provides oil with a certain amount of lead and iso-octane. The blended product must contain a maximum of 3.5% lead and a minimum of 65% iso-octane. The refinery wishes to purchase a…
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Is it possible to slove problem with norm constraints using only linear programming?

The problem is $\min_x w^Tx$ s.t. $Ax=b$ $||x||_2=1$ Is there any tricks to handle the norm constraints such that the problem can be solved by only using linear programming tools?
Rein
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Mixed linear programming if...then

I need to model the following statement: if $\sum\limits_{i=1}^N X_i=k$ then $Y=1$ else $Y=0$ $X_i$'s are binary variables $k$ is an integer between $0$ and $N$ $Y$ is a binary variable Thank you in advance.
Sou
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How can this linear problem be infeasible?

I have the following linear problem which is primal: I have converted this problem to its dual and tried to solve using the lpSolveAPI in R programming language. However, the solve function returns a 2, which means the problem is infeasible. It is…