Questions on linear programming, the optimization of a linear function subject to linear constraints.

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1answer
27 views

Linear optimization problem with additional constant cost for non-zero variables

I have a linear optimization problem with integer variables of the form minimize $a_1 x_1 + ... + a_n x_n$ under a set of constraints Bounds for each variable $a_i \le constant_i$ Bounds for ...
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0answers
25 views

Feasible set for linear system with linear constraints

I have a linear underdetermined system $Ax = b$ with constraints $0 \le x \le 1$. Matrix $A \in \mathbf{R}^{n \times m}$ with $n < m$, elements of which are either $0$ or $1$, and sum of each ...
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34 views

how to solve a simplex with n variables

I don't know how to resolve a simplex with n variables I have this primal problem \begin{cases} \text{min}& z=-x_1 - x_2 -... - x_n\\ &a_1x_1 + a_2x_2 +... + a_nx_n \le 1\\ &x_1... ...
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33 views

A System of Inequalites arising from the Divisors of a Number, Showing Its Non-Solvability

Let $n$ be a natural number. Denote by $d(n)$ the number of divisors of $n$, i.e. with the notation from Wikipedia:Divisor Function we have $d(n) = \sigma_0(n)$. Suppose we have the $d(n) - 2$ ...
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1answer
46 views

How to test if a feasible solution is optimal - Complementary Slackness Theorem - Linear Programming

I have this linear program $$\begin{cases} \text{max }z=&5x_1+7x_2-3x_3\\ &2x_1+4x_2-2x_3&\le8\\ &-x_1+x_2+2x_3&\le10\\ &x_1+2x_2-x_3&\le6\\ &x_1,\,x_2,\,x_3\ge0 ...
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19 views

Interpretation of the dual of shortest path problem

I am trying to find an interpretation of the dual of shortest path problem of the form: $ maximze \; y_s - y_t$ subject to $y_i - y_j \leq c_{ij}$ $y_i$ are unrestricted, $c_{ij}$ being the cost ...
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13 views

Am I understanding this question correctly? Linear programing

A company produces and sells two products A and B. Let x denote the number of items of product A and let y denote the number of products of product B. The profit is DKK 30 per unit of product A and ...
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1answer
43 views

If we start with a feasible tableau in simplex method, are we basically generating a different feasible point in every pivot step?

This is a true and false question. The actual question reads: "In solving a linear program by the simplex method, starting with a feasible tableau, a different feasible point is generated after every ...
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8 views

How to test if a set of underdetermined equations have solution in a particular region?

For a underdetermined system $A\cdot x = b$ where $A$ is a $m \times n$ matrix with $m<n$, how to test if it has a solution within a specific region $\{ x | lb<x_i<ub \}$? Basically I have ...
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1answer
18 views

finding a plane in R3 given 5 points

I have multiple vertices that I need to create a plane out of. What is a formula/method for having a plane that contains 5 points? I believe I could use just 3 and the other two will be included
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1answer
26 views

Matrix that doesn't lose zeros

I have a vector $\vec x$ with some entries that are zero, and I apply a linear transformation so that for some matrix $A$, $A \vec x$ = $\vec b$. I would like to find a matrix $A$ (or better yet, ...
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13 views

Give a solution set of a dodecahedron [duplicate]

Using basic inequalities, find a set of inequalities so that the set of all solutions is a dodecahedron with twelve pentagons for sides.
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28 views

How can I find multiple solutions for a system of equations?

I'm writing a program for CheckIO.org that is supposed to return an array, $$ \begin{bmatrix} x\\ y\\ z \end {bmatrix} $$ , that satisfies the System of Equations $$ A \begin{bmatrix} x\\ y\\ z \end ...
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38 views

The set of all vectors satisfying $Ax\ge\vec{0}$

Consider a rectangle matrix $A\in\mathbb{R}^{m\times n}$ with $m\ge n$, and the set of all vectors $x\in\mathbb{R}^n$ satisfying $Ax\ge\vec{0}$. I note this set is closed under multiplication by a ...
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0answers
17 views

Uniqueness of Solution in infinite linear programming

I would like to ask about a sufficient condition under which a solution for an infinite linear programming is unique. In standard finite dimensional linear programmings, like $\min_x p\cdot x$ ...
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2answers
44 views

Setting up a linear programming word problem

Problem: A metalworking shop needs to cut at least 32 large disks and 219 small ones. There are three cutting patterns for the standard size metal rectangle. One cutting pattern produces two large ...
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17 views

How is the pivot chosen for the symbolic weights for the Cassowary algorithm?

I am trying to understand The Cassowary Linear Arithmetic Constraint Solving Algorithm, and I am having trouble understanding symbolic weights, starting in section 2.3. Working through the example, ...
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1answer
49 views

Linear Programming - deriving the Dual of the Primal

I've the following linear programming problem: This is the LP representation of the uncapacitated facility location problem. This is the dual representation of this problem: My question is how ...
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7 views

Linear Programming Neighborhood Problem 2

Suppose we are given a set of 2n integers and we wish to partition into 2 sets $S_1$ and $S_2$ so that |$S_1$|=|$S_2$| and so that sum of number in $S_1$ is as close to sum of numbers in $S_2$.Let ...
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18 views

Linear Programming Neighbourhood problem

In the n-city TSP what is the cardinality of $N_2(t)$ , the neighborhood of tour t determined by 2 change? What is the cardinality of $N_3(t)$?
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1answer
39 views

Primal feasible solution implies Dual optimal solution?

Every feasible solution of P puts an upper(or lower, depending on whether it is a maximization or minimization problem) bound on the optimal solution of D(assuming of course that D has a feasible ...
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1answer
40 views

Mixed Integer Linear Programming: Construction Rods

I have an interesting problem involving linear programming. The problem is the following, I have 4 different kinds of rods (rod sized found in the local market): 9m rod 11m rod 12m rod 15m rod ...
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1answer
16 views

Conditions for a LP to be integral

What are the conditions to be met by a LP that allows to infer that its optimum solution will be integral? Is total unimodularity a necessary and/or sufficient condition? What if all variables are ...
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1answer
20 views

LP Word Problem Construction

I am having difficulty constructing the constraints on a word problem as follows: The Brite-lite Company receives an order for 78 floor lamps, 198 dresser lamps, and 214 table lamps from condoski ...
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29 views

Indicator Variable, Mixed Integer Linear Programming

Assume $x$ is a real variable, and $0\leq x \leq1$. Besides, $y$ is a binary random variable. I need a linear program that: if $y$ is $1$: $x>0$, if $y$ is $0$: $x=0$ I know the following ...
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1answer
21 views

Solving a linear program using just one call to a procedure that gives a feasible solution.

Suppose we have some procedure $F$ which takes any set of linear constraints and either returns either infeasible or returns a vector satisfying these constraints. If we now take a linear program ...
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1answer
32 views

linear programming problem solving

I have written in lp solve and obtain the solution of 0.58 highqualitymeat and 0.41 lowqualitymeat the thing that confuses is doing it through a graph as: let x be high quality meat and y be low ...
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14 views

Linear programming and complementary slackness

If there's a given basic solution $ A = (x,w)$ for the primal problem (where $x$ are decision variables and $w$ are slacks), I can determine the dual variables $y$ and slacks $z$ associated with B.S. ...
4
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1answer
32 views

Maximize $Z=-x+2y$ given $x\geq 3,\ x+y\geq 5,\ x+2y\geq 6,\ y\geq 0$

I am a highschool senior that's new to this topic. So, apologies for my lack of knowledge and misconceptions. The proof of the theory of this chapter is beyond the scope of my textbook, so that may be ...
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1answer
22 views

Linear Programming:What combination of two loams to minimize cost

I am fairly new to linear programming so simplification would be helpful.Came across a certain question and unfortunately no answer for it at the back of the book. The question is adopted from a book ...
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2answers
29 views

Prove linear program is unbounded

So I need help on my homework (I feel like a 10 year old). The exercise goes like this: Prove algebraically that the following program is unbounded: Max: $x_1 - x_2$ Constraints: $-2x_1 + x_2 ...
2
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1answer
122 views

Lemke-Howson pivoting in degenerate bimatrix games

I'm working on an implementation of the Lemke-Howson algorithm for finding Mixed Nash Equilibria of bimatrix games, and I'm running into a roadblock when the algorithm is fed a degenerate game. For ...
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25 views

Feasibility Sets for Integer Program

I have two set of constraints defining feasibility sets $A$ and $A'$ of a mixed integer program. $x_{i}, y_{ij}$ are continuous positive variables, $a_{ij}, b_{ij}, c_{ij}, d_j$ are known ...
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1answer
25 views

A linear program for maximizing a fraction

Given $\lambda_1,\ldots,\lambda_n \geq 0$ and an $n\times n$ matrix $A$, I wish to maximize the ratio $$ \frac{\lambda_1x_1 + \cdots + \lambda_nx_n}{x_1+\cdots+x_n}, $$ where $x_1,\ldots,x_n \geq 0$ ...
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24 views

simplex algorithm with tableau

in the picture below you can see the tableau representation of a linear programm with a coefficient $b\in \mathbb{R}$. BV stands for basic variable. For which $b$ is $y_1=\frac{1}{2}, ...
2
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1answer
43 views

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 ...
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1answer
22 views

LP program: does the decision variable coefficients affect the problem?

I just started reading up on linear programming by myself, and am a bit confused by the decision variable coefficients $c_j$, in the objective function $ \sum_j c_jx_j$. Do they matter? I mean, if ...
3
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1answer
58 views

What gambling/board game or real life thing can (surprisingly) be modelled as a linear programming problem?

So I've taken Linear Programming 101. I've read my textbook, took the test and all that, and - besides all the theory, the nice algebraic interpretations, etc - I've encountered a lot of textbook ...
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139 views

duality theory question

Let $A$ be a given $m$ x $n$ matrix, and $c\in R^n$ and $b\in R^m$ be given vectors. Use LP duality theory to show that if the problem $$\min\{x^Tx: Ax=b, x\geq0\}$$ has a finite optimal solution, ...
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42 views

extreme points and representing

$$X=\{(x_1,x_2)^T : x_1-x_2\leq3, 2x_1+x_2\leq 4, x_1\geq -3\}$$ Find all extreme points of $X$, and represent $x^*= {0\choose1}$ as a convex combination of those extreme points. I sketched it out ...
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37 views

L_1 norm optimization as a sequence of linear optimizations?

Does someone know of numerical methods to approximately solve ${\bf x_0} = \min_{\bf x}\{ \left\|\bf Mx - b\right\|_1\}$ by using some sequence of linear optimizations? Links or ideas are both ...
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0answers
28 views

Computing a lower bound for the minimal componentwise distance of vertices of polyhedra

Let $A$ be a matrix in $\mathbb{R}^{m \times n}$ and let $P = \{ x \in \mathbb{R}^n \mid Ax \leq b \}$ be a polytope. I want to compute a lower bound on the minimal componentwise distance of two ...
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79 views

Linear programming optimization problem formulation

I need help in formulating an optimization problem. I have a system of equations as follows: $c_1x_1+c_2x_2+c_3x_3=1$ $b_1x_1+b_2x_2+b_3x_3=1$ $a_1x_1+a_2x_2+a_3x_3=1$ In my case the ...
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1answer
23 views

Why is a local min also a global min for convex functions?

As the title states, for an unconstrained minimizaton problem, of a convex function, why is it that the local minimum is also the global solution?
2
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1answer
34 views

How does the Simplex method handle test ratios with zeros?

I've been running into an issue choosing a pivot when there are constraints with an RHS of zero. It appears that sometimes you should include zero test ratios when searching for the minimum test ...
2
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2answers
52 views

Integer Linear Programming

Without using a computer, I have to solve the following integer linear programming:$$\min \quad x_1+x_2+x_3$$ $$\operatorname{sub} ...
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2answers
25 views

If $\phi$ is injective linear map $\mathbb{R}^r \rightarrow \mathbb{R}^s$ then $Im \phi$ is closed in $\mathbb{R}^s$

My optimization theory handbook says that If $\phi$ is injective linear map $\mathbb{R}^r \rightarrow \mathbb{R}^s$ then $Im \phi$ is closed in $\mathbb{R}^s$, where $Im \phi$ denotes image of map ...
1
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1answer
44 views

Prove a property of primal-dual problems

When I was studying the computation aspects of quantile regression, I consulted some linear programming book and found an interesting property as follows: If the primal problem have unbounded ...
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1answer
34 views

$ \mathbb{F} = \{x \in \mathbb{R}^n:Ax=b\}= \mathbb{F}_r=\{x \in \mathbb{R}^{n}:A^{(r)}x=b^{(r)}\}$

Show that these two sets are equal. $A$ is an $m\times n$ matrix of rank $r$, $b \in \mathbb{R}^m$. $A^{(r)}$ denotes an $r\times n$ matrix with $r$ linearly independent rows of $A$ and $b^{(r)}$ is ...
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39 views

Systematic Gaussian elimination on a binary matrix?

I am trying to understand the mathematics behind the lights out puzzle (http://mathworld.wolfram.com/LightsOutPuzzle.html). There's a very helpful webpage at ...