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:

5084 questions
0
votes
1 answer

Convert linear programming problem

Suppose x is the solution to a standard linear programming problem ($Ax=b$, $x>=0$) and the set $S$ is every $i$ where $x_{i} = 0$. How can I show this is optimal only where minimize $c'f$ subject to $Af=0, f_{i} \ge 0$, $i$ is in $S$ has a cost of…
GBa
  • 1,046
0
votes
1 answer

For which values of $a$ does the following LP problem have an optimal solution?

Let $a \in R$. For which values of $a$ does the following LP problem have an optimal solution? $$max(2x_1+6x_2+3x_3)$$ $$-3x_2+ax_3 \geq 3$$ $$x_1+5x_2+2x_3=4$$ $$x_1, x_2, x_3 \geq 0$$ I solved it with the Big M Method and found that the LP problem…
Mary Star
  • 13,956
0
votes
2 answers

Transportation problem in supply chain

I understand how to solve transportation problem with only members in the chain, but how can I solve the transport problem with multiple members in the chain? Thank you.
0
votes
1 answer

Definition of an active hyperplane

We are learning about the Geometry of Duality in Linear Programming, and my prof uses the terminology active hyperplane. I'm wondering what the formal definition of this is. I can't seem to find any other references to this online. From my…
MITjanitor
  • 2,690
0
votes
3 answers

Introducing slack variables in LP

I am learning about the Simplex Algorithm. I learned that we can turn an inequality constraint of the form $a_i x_i \leq b$ into an equality constraint $a_i x_i + s = b$ with $s \geq 0$. I do not know why and when should we do this?
ZonghanXU
  • 111
0
votes
0 answers

travelling salesman

I am trying to program TSP problem in R. From wikipedia page section "Integer linear programming formulation", I was able to understand all the constraints except the last one. Need help to understand the last constraint...what are the variable…
user98812
0
votes
0 answers

Linear Programming: Maximize z = 5x + 4y with Non-Strict Constraint (Graphical Solution)

Problem: Maximize z = 5x + 4y Subject to: x + 2y >= 24 (Constraint 1) 3x + y <= 6 (Constraint 2) x + y <= 4 (Constraint 3) x >= 0 (Non-negativity constraint for x) y >= 0 (Non-negativity constraint for y)
0
votes
1 answer

How to convert a primal LP into the dual LP without usage of the standard form?

To understand the conversion without standard form I read: Directly from primal to dual when primal not in standard form The posted LP there is: $$ Primal =\begin{Bmatrix} max \ \ \ \ 2x_1 - 2x_2 +x_3 + 4x_4 \\ s.t. \ \ \ \…
0
votes
1 answer

Primal to Dual conversion Linear Programming non-standard form

I've come across a problematic LP question and unfortunately it's been a while since I solved these type of problems the problem: you have a graph $G$, the edges are $E$, Vertices are $V$, edges are denoted by $(u,v)$ : \begin{align} \max…
0
votes
0 answers

Prove $Ax\leq b$ for $A=\begin{pmatrix} 1 & -1\\ 1 & 1\end{pmatrix}$ and $b=0$ is not total dual integral

I need to show that $Ax\leq b$ for $A=\begin{pmatrix} 1 & -1\\ 1 & 1\end{pmatrix}$ and $b=(0, 0)^T$ is not total dual integral. So I have calculated that $Ax\leq b$ holds only when $x_1\leq 0$ and $x_1\leq x_2\leq -x_1$.I consider $A^Ty=c$ for…
toki
  • 95
0
votes
0 answers

Why are shadow prices the optimal solution of the dual

Consider an LP $\max_x c^t x$ s.t. $Ax \leq b, x\geq 0$. Let the dual problem be $\min_v b^t v$ s.t. $A^\top v \geq c,v\geq 0$. It is stated in standard text book that the shadow prices of constraints in the primal problem are exactly $v^*$, the…
Yining Wang
  • 1,279
  • 7
  • 23
0
votes
2 answers

Linear program with unknown coefficients in objective function

I was given the following linear program $ \begin{align} \alpha x_1 + \beta x_2 &\rightarrow \max \\ -3x_2 &\le -9 \\ -x_1-2x_2 &\le -12 \\ -x_1-x_2 &\le -8 \end{align} $ where $\alpha$ and $\beta$ are real parameters. The question states the…
0
votes
0 answers

Linear programming model

I am writing a linear programming model with two decision variables for the follow scenario but am having trouble structuring it. Here is the set up: A company is going to rent machines that produce widgets and has $\$5000$ to spend. Large…
gunsnfloyd
  • 35
  • 4
0
votes
1 answer

How to identify a CPF solution in an LP model?

"For any linear programming problem with n decision variables, each CPF solution lies at the intersection of n constraint boundaries; i.e., it is the simultaneous solution of a system of n constraint boundary equations. However, this is not to say…
0
votes
0 answers

Factory Worker Problem on Linear Programming

Actual Question Statement: In a factory there are 100 skilled and 125 unskilled workers. Two different goods A and B are produced. 2 Skilled and 5 unskilled workers can produce one unit of A per day using 10kg raw material and 175 units of…
SubbSE
  • 1