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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vogel approximation and dummy column

I am solving a linear programming problem for transportation and have to use the VAM method, vogel approximation. As the problem is unbalanced, I know that I have to add a dummy column to balance it. When I calculate the penalty if I consider the 0…
jsab
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Farkas with strict inequalities

I have proven the following result. Let $a_i \in \mathbb{R}^n$ for $i = 1, \ldots, m$. Then precisely one of the following statements is true. $$\text{(1) } c^t x < 0, \: a^t_i x \leq 0 \text{ has a solution } x \in \mathbb{R}^m$$ $$\text{(2) }…
user119470
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Given a feasible solution to an LP, how to determine if it is basic?

How can I tell if the given solution is basic?
cjbrog
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Objective function Convex proof

This is a question from the textbook that I can trying to figure out. Show that the objective function $$z = c^{T}x $$ of a linear programming problem is a convex function I know that $$z = c_{1}x_{1} + .... + c_{n}x_{n}$$ is definition of…
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Graphing Piecewise Linear Convex Function

In the lecturer's notes, we say the $$\max_{i = 1,\ldots, m}(c_i^T x + d_i) $$ is a piecewise linear convex function and the notation $$\max_{i = 1,\ldots,m} $$ for the maximum value among $a_1, a_1,\ldots, a_m$ How do you sketch the graph $$y =…
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Basic Solutions and Linear Optimization

\begin{bmatrix} 1& 1& 1& 0& 0\\ 0& 1& 1& 0& 0\\ 0& 0& 1& -1& 1 \end{bmatrix} This problem is related to Linear Optimization where this matrix is labelled as Coefficient Matrix A and I am expected to find all the basic solutions to this…
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Equalizing sums of subsets into X buckets

I've used Excel to do some linear programing, and I've found some Java libraries that can help with this, but I'm not sure linear programming is the right solution, or that the available libraries can handle what I'm trying to do. I have a number of…
Adam
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primal simplex procedure

Minimize $-2x_1-x_2+2x_3$ subject to $x_1 +x_3 = 4$, $-2x_1 +x_2 = 8$ s.t. $x_1,x_2,x_3\geq 0$. In my book, the augmented matrix is defined as $[A : 0 : b; -c^T : 1 :0]$ (where : separates columns and ; separates rows). Since the matrix of…
Emir
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Deduce LP maximization problem from sensitivity analysis

I have the answer to and the sensitivity analysis for a LP maximization problem. (See picture) http://postimg.org/image/xs4iowbrj/ How can I deduce the original LP problem? I have figured out this: Max Z = 5x1 + 4x2 + 3x3 + 4x4 a1x1 + b1x2 + c1x3 +…
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Fundamental Theorem of Linear Programming

I'm reading Dan Stefanica's book "A Linear Algebra Primer for Financial Engineering", which says in pp 92, $\S3.2$ that "...the Fundamental Thorem of Linear Programming, which, informally speacking, states that, if a set of linear inequalities…
athos
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Linear programming: Condition on index variable

Let $i \in \{1,2,...n\}$. And let $X_i \in \{0,1\}$. I need to write the condition: if all $X_i$ where $i$ is even index take the value 1, then there need to be at least three $X_i$ with value $0$ for all $i$'s with odd index. The problem I am…
Zenga
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Strong duality theorem written with iffs?

Our strong duality theorem is: If both the primal LP and the dual LP have feasible solutions, then they both have optimal solutions, and for any primal optimal solution $x$ and dual optimal solution $y$, we have $c^Tx=b^Ty$. Can this be written…
snowman
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creating a set in ZIMPL (which creates .LP for SoPlex & CPLEX)

I am looking for some help creating a set dynamically in ZIMPL. I have a parameter table: param Q[W*W] := |1,2,3,4,5| |1|1,1,0,0,0| …
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Revised Simplex Method w/o Identity Matrix

For a homework problem we're forced into using revised simplex, but I cannot seem to even get past the first step. My biggest problem is: max z = 2x1 + 3x2 -x3 subject to: x1 + 2x2 <= 3 2x1 + 3x2 <= 6 3x1 + 2x2 + x3 = 10 I know that this goes…
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Linear Programming $\boldsymbol{c}^T \boldsymbol{x}$ s.t. $\boldsymbol{Ax} = \boldsymbol{b}$

Prove for the linear programming \begin{equation} \left\{ \begin{array}{cc} min & \boldsymbol{c}^T \boldsymbol{x} \\ s.t. & \boldsymbol{Ax} = \boldsymbol{b} \end{array} \right. \end{equation} has only two results: the objective function dose…