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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Chosing an objective function to avoid optimal values having variables as zeros

Let's assume I have a sequence of non-overlapping tasks of type X and Y mixed. I have various runs of such sequences where it is known how many times Xs and Ys were executed as well as the approximate total runtime of the sequence. I'd like to…
akarnokd
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find slack form of given optimal solution to LP that is BFS

Given LP in standard form with $n$ variables and $m$ constraints. And given $(x_1,...,x_n)$ optimal solution that is bfs of some slack form. How can I find the slack form in $O(n^2m)$? I know that that the BFS contains at least $n$ zeros (and at…
Nitz
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Solve following Linear Programming Problem(LPP) using Graphical method

Solve this Linear Programming problem(LPP) using Graphical method : $F=2x_1-x_2-2x_3+6x_4$ $x_1+x_2+x_3+3x_4=16$ $-x_1+x_2+3x_3-x_4=8$ $x_1\geq0 ;x_2\geq0;x_3\geq0;x_4\geq0$ Max $F=?$ I've searched and learned that graphical method can be use when…
Zenit
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Dictionaries which share Basis, are they the same?

I am (trying) to understand the following theorem: If the simplex method does not terminate, it must cycle Now I know that two dictionaries with the same $\mathcal{B}$ have to be encountered because the possibilities we have for that is not…
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Move to LP corner point from feasible solution in plane.

I have a feasible solution for a linear programming problem that is not necessarily a corner point. What algorithm can I use to move to a corner point feasible solution from this solution, so that I can then use this as a starting point for the…
Dylan
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What should I do about equality constraint

I have this problem to be solved using the dual simplex method. I'm confused right now because there are a lot of different methods I've searched online. What are the steps in solving the problem using the dual simplex method, and what should I do…
Blake
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How to solve a linear program with a separable objective function?

The following is problem 4.11(b) on p. 193 of Boyd and Vandenberghe's Convex Optimization, Cambridge University Press, 2004. Let $A \in \mathbb{R}^{m\times n}$, and $b \in \mathbb{R}^n$. For every $y \in \mathbb{R}^m$, define $\|y\|_1 :=…
Evan Aad
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How does writing $x = x^{+} - x^{-}$ in LP guarantee us that the optimum does not change?

In Linear Programming, we sometimes write $x = x^{+} - x^{-}$ such that $x^{+}, x^{-} \geq 0$ when $x$ is not bounded on either side. How does this guarantee that the optimum solution does not change (for both maximization and minimization), that…
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Dual transportation problem in general case

I have the following problem: For the given natural $n$ find the maximum value of the target function $\sum_{i=1}^n u_i + \sum_{j = 1}^n v_j \rightarrow max$ subject to $u_i + v_j \leq 2^{i + j}$ for $1 \leq i, j \leq n$ As far as I know such kind…
Gleb Chili
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Constraint analysis in a linear programming problem

I have some doubts about the approach to the constraints in this linear programming problem. A company manufactures domestic fans. It currently markets fans in three different sizes: A, B and C which provide a net profit of €30, €36 and €42,…
cooper
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Basic Directions at a Point

Suppose we have $$ \begin{equation} P=\begin{cases} x+y+z=2\\ x,y,z \geq 0 \end{cases} \end{equation} $$ For the resulting matrix $[\ 1 \ 1 \ 1 \ ]$ I know $n=3, m=1$. If there is a BFS, $C = (0, 0 ,2)$. How do I find the basic…
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Conditional constraint LP

My question is fairly basic: how can I express a conditional constraint in a LP? Example: I have a minimization of cost of production at a company. My company either can produce up to 100 bikes with a minimum of 25 for that month or doesn't produce…
Raul M.
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How to find if an extreme point is degenerate algebraically?

Is there a method to algebraically determine if an extreme point is degenerate? Can someone please explain to me. Here's my example: $$\max x + 2y $$ subject to, \begin{align} x - 4y &\leqslant 4 \\ -2x +y &\leqslant 2 \\ -3x +4y &\leqslant 12…
norma
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How to show one problem is relaxation of another?

I am new in stackexchange. I am having difficulty in answering the following question in Wolsey's Integer Programming Book. enter image description here I know that I can call P2 a relaxation of P1 if the feasible set in the former is larger or the…
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Linear optimization with matrix constraint

I encountered a linear optimization problem which looks like the following: Let $W^* = \{w^*_{ij}\}$ be an $n\times n$ real matrix with $w^*_{ij}\geq 0, \forall i, j$. $$\underset{W_{n\times n}}{argmin \hspace{1mm}} 1^T W 1\\ s.t. W\geq 0, \\ (W -…