Questions tagged [linear-programming]
Questions on linear programming, the optimization of a linear function subject to linear constraints.
5,211 questions
2 votes
1 answer
56 views
How to find Farkas certificates?
Farkas Lemma: Let $A$ be an $m \times n$ matrix, $b \in \mathbb{R}^m$ and $$F = \{x \in \mathbb{R}^n: Ax = b, x \ge 0\}.$$ Then either $F \ne \emptyset$ or there exists $y \in \mathbb{R}^m$ such that ...
0 votes
1 answer
67 views
Case where infeasibility comes from $Ax=b$ unmet in standard polyhedron not handled in this proof?
In linear optimization, a solution that is not feasible can be so because it violates an equality constraint, isn't it? Be it an equality constraint from a non-standard polyhedron or an equality ...
0 votes
0 answers
32 views
How to represent a standard linear program (LP) as a semidefinite program (SDP)?
I'm trying to understand how to express a simple LP in the standard semidefinite programming (SDP) form. In particular, consider the following linear program: $$ \begin{aligned} \min_{x_1, x_2} \;&...
1 vote
1 answer
75 views
Span of integer valued elements in $\ell_1(\mathbb{N})$
Consider the real Banach space $\ell_1(\mathbb{N})$, further denoted just $\ell_1$, consisting of all functions $x: \mathbb{N}\to\mathbb{R}$ such that $\|x\|:=\sum_{n=1}^\infty |x(n)|<\infty$, ...
2 votes
1 answer
97 views
Simplex Method - How to know which basis to choose after the first iteration?
I'm trying to understand how to correctly choose the next basis after the first iteration in the simplex method. In my problem, I have the following minimization form: $$ \begin{aligned} \min z &= ...
1 vote
1 answer
56 views
Linearization Question for max-min|x| Bi-level Optimization Problem
I'm currently working on a bi-level optimization problem with the following structure: max min |x| I attempted to linearize this problem using the following approach: Introduce an auxiliary variable ...
0 votes
0 answers
46 views
Book proves Weak Duality using Strong Duality and proves SD using WD ? Circular argument?
The proof of weak duality in my book starts with arguing that $p_i$ and $a_i' x -b_i$ have the same sign (and analogously that $x_j$ and $c_j - p' A_j$ have the same sign). This observation is based ...
4 votes
1 answer
290 views
Winnability of an urn-ball game with restricted two-urn moves
My question is about a certain combinatorial game. The game works as follows. We have $n$ urns, each of which contains $m$ balls, where $m$ and $n$ are positive and satisfy $m < n$. A move consists ...
0 votes
0 answers
49 views
How to see $x_1\geq 0$ in the primal implies $p' A_1 \leq c_1$ in the dual, when there are no other constraints than just $x_1\geq 0$?
I understand why the constraint $x_1 \geq 0$ in the primal, implies $p'A_1 \leq c_1$ in the dual in the presence of a constraint involving an $A$ and a vector $b$ in the primal ($A_1$ being the first ...
0 votes
0 answers
18 views
Fourier-Motzkin Elimination for Single Vertex Computation
Given a convex polytope $P = \{ x \in \mathbb{R}^n \mid Ax \leq b \}$, I want to know whether we can use Fourier-Motzkin elimination (or an adaptation therefore) to compute one vertex of $P$ (or to ...
0 votes
1 answer
72 views
Book from Bertsimas suddenly switches from $(m+1)$ basic points to $m$ basic points in a problem that requires $(m+1)$ basic points
In the section $3.6$ of the book Introduction to Linear Optimization (Bertsimas and Dimitris), the column geometry of the simplex method is explored. It starts with the fact that any bounded ...
0 votes
1 answer
102 views
How many big and small marbles are not used?
Translating to English from a non-English physics book about measurements: Anif has $8$ big marbles and $15$ small marbles. The weight of the big and small marbles are $37.5$ and $12.5$ respectively. ...
2 votes
0 answers
25 views
Does the Interior Point Method Solve Klee-Minty Cubes adversarial instances in Polynomial Time?
I am a network engineer currently studying optimization problems. Out of curiosity, I was fascinated by the fact that the Simplex Method has an exponential worst-case complexity, a property famously ...
2 votes
0 answers
37 views
Understanding changes in a polyhedron structure when there are perturbations on the restrictions vector
I have the polyhedron $$ P := \left\{ {\bf x} \in \mathbb{R}^{\binom{n}{k}} : {\bf A} {\bf x} = {\bf b} , \hspace{0.3em} {\bf 0} \leq {\bf x} \leq {\bf 1} \right\} $$ where the matrix ${\bf A} \in \...
1 vote
0 answers
29 views
When do linear constraints form a compact? [closed]
Given a list of constraints $$ F_i = \{ x\in\mathbb{R}^n\mid L_i(x) \leq c_i \} $$ where $L_i\in L(\mathbb{R}^n,\mathbb{R})$ and $c_i\in\mathbb{R}$ for every $i\in\{ 0,\dots,m \}$ with $m \geq n$, ...