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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Generating multiple pages with multiple numbers

This question is mainly related to programming else than just only a math problem, I am developing a system where there will be multiple pages of contents, the contents are coin types and I need to generate a page showing those coin types, the main…
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Linear Programming: understanding a special maximum-ratio rule for deciding a leaving variable

In my book, the following rule for choosing a leaving variable is given: $$x_k=\big(\max_{i\in B}\frac{\bar{a}_{ik}}{\bar{b}_i}\big)^{-1}$$ $$$$ But let us say you get the following scenario: $$ratios_1 = \big(\frac{-3}{4}, \frac{-7}{3},…
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Feasible solution with strictly negative reduced costs

My question is: Show that a degenerate basic feasible solution can be optimal without satisfying $r_j \geq 0$ for all $j$, i.e. there can be strictly negative reduced costs. I can't seem to find any information regarding this. I'm having a really…
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Linear Programming constraints clarification

Given https://machinelearninggeek.com/solving-staff-scheduling-problem-using-linear-programming/ this case on scheduling, Can someone explain constraints 1, the latter $3$? Where on constraints 2 is $x_3$ if $x_2$ is also considered? I played…
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My linear program has multiple optimal solutions. I want that corner point at which the value of one of the variables is the maximum?

Is there a way to find the optimal point with this special property in polynomial time? Note that the polytope in the linear program may be unbounded.
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Is $\{ x \in \mathbb{R}^2 \mid x \ge 0, v^Tx \le 1 \quad (\forall v \in \mathbb{R}^2 : \lvert\lvert v \rvert\rvert = 1) \}$ a polyhedron?

I am working on the following exercise: Consider $$P := \{ x \in \mathbb{R}^2 \mid x \ge 0, v^Tx \le 1 \quad (\forall v \in \mathbb{R}^2 : \lvert\lvert v \rvert\rvert = 1) \}$$ Is $P$ a polyhedron? I think that $P$ is not a polyhedron since there…
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Why is $Ax \leq b$ is equivalent to $A'x' = b'$ and $x'\geq 0$

I am getting confused in LP conversion from one form to another. Say, I have an LP of the form $Ax\leq b$ and I want to convert it into the form $A'x'=b', x'\geq 0$, how to do this? For example let's say the equation is $3x+2y\leq 10$, we can…
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two linear programs, one unbounded, one feasible and bounded

I've been biting my teeth out, trying to find an example of the following. Is it even possible? Consider two LPs $$ (P1) \ \max \{c^Tx|Ax\leq b, x\geq 0\} \\ (P2)\ \max \{c^Tx|Ax\leq \tilde{b}, x\geq 0\} $$ where $ A \in \mathbb{R}^{m,n}$, $c\in…
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Understanding an LP where every feasible solution is optimal

I'm trying to study for a linear programming exam and I came across this statement: "For a linear program in standard form with coefficient matrix A, if the cost vector c belongs to the row space of A then every feasible solution is optimal." I…
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I solving the dual often faster than solving the primal and vice versa?

I am solving a large number (probably millions a second, maybe billions) of feasibility problems: $max\ 0$ subject to: $Ax \ge -b,x\ge0$ So the dual is highly degenerate but is already an initial feasible solution. $max\ -b^Ty$ subject…
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How to prove this LP problem?

Prove that any LP optimization problem can be transformed into the following form: \begin{align*} \text{minimize} && 0 · x \\ \text{subject to} && Ax &= b\\ && x&\ge 0 \end{align*} If the LP is feasible, then it has an optimum value of 0 If…
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Show that a set S in R^n is convex if and only if every convex combination of a finite number of points in S is in S.

I am stuck on the first direction of the if and only if statement: Let K be an arbitrary number of points in S S is a convex set $\rightarrow$ $x' = \sum_{i=1}^k c_ix_i\in S$ and $\sum_{i=1}^k c_i = 1$ If I'm understanding this question correctly,…
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Linear Programming Constraint Percentages

I have a homework about linear programming. I have to formulate the constraint of the following: A company produces two products, Deluxe and Special. The company decided that the Special must comprise at least 40 percent of the production total. I…
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Constraints in Excel Solver

I am using Excel Solver. I have decision variables $A$, $B$, $C$, $D$, $E$ with the constraints that $A \leq B \leq C \leq D \leq E$. How do I specify this type of constraint in the Solver dialogue box. Update 10/3: Yes, that makes sense and I…
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Extreme point theorem of linear programming

So I was told to find a counterexample to this linear programming extreme point theorem: "If $S$ is nonempty and not bounded and if an optimal solution to the problem exists, then an optimal solution occurs at an extreme point." Is there any hint?…