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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Solving a linear programming problems is no harder than solving systems of linear inequalities

Suppose that we are given a subroutine which, given a system of linear inequalities $Ax \leq b$, $x \in \mathbb{R}^n$ , either produces a solution or decides that no solution exists. I would like to construct an algorithm that uses a single call of…
Santos
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What is $ {z_j} $ in this tableau? (Simplex algorithm)

I've hightlighted the section in the tableau I don't understand. Clearly the 28 comes from plugging in the 4 and 2 in the objective function but where do the other numbers in the row come from? Any help is appreciated. EDIT: Oh, the objective…
MathGuy
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Does a production mix of good A and B exist that uses up all resources

Given that a firm produces goods $A$ and $B$, using inputs $F$ and $G$.Each unit of $A$ requires 8 units of $F$ and 10 units of $G$. Each unit of $B$ requires 4 units of $F$ and 15 units of $G$. There is a total of 240 units of $F$ and 600 units of…
Andrew Brick
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How to Formulate the given Linear programming program

Chemlabs produce the domestic cleaning solutions $A$ and $B$ by processing the raw materials for $I$ & $II$. The processing of $1$ unit of raw material $I$ costs $\text{Rs. }80$ and produces $0.5$ units of solution $A$ and $0.5$ units of solution…
Kavita
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Formulation of Linear Programming Problem

A company produces two types of hats. Each hat of the first type requires twice as much labour time as does each hat of the second type . If all hats are of the second type only, the company can produce a total of 500 hats a day. The market limits…
Kavita
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Find the dual of the following linear program

Let $A$ be a real $m \times n$ matrix, and $l, u$ be two column vectors with length $n$. Suppose also that $m < n$. Find the dual of the linear program min $c^Tx$ st $Ax = b$ and $l <= x <= u$ I got stuck so badly of the last constraints on $x$.…
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Help with Min Ratio Test in Phase II

How can you prove that the min ratio test in phase II in the simplex algorithm ensures that a feasible tableau remains feasible on pivot in linear programming?
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Sufficient conditions for integer extreme points in linear programming

I was given an exercise that looks as follows: Given the following linear program: minimize $\sum_{i=1}^{m} y_{i}x_{i}$ subject to some constraints related to $x_{i}$, prove that any extreme point of the feasible region of this linear program…
ksm001
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best method for solving fully degenerate linear programs

I am looking for efficient computational methods for solving a class of linear programs whose right hand side is zero: $$ \min c^T x \qquad\text{ subject to }\qquad Ax\ge 0 $$ What is the best general purpose algorithm for solving such linear…
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How to have just 3 result variables for this linear programming problem?

I have the following problem: +----------------------+--------------+--------------+----------+ | Process time (hours) | +----------------------+--------------+--------------+----------+ | Product …
juliano.net
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Techniques for (upper-)bounding LP maximization

I have a huge maximization linear program (variables grow as a factorial of a parameter). I would like to bound the objective function from above. I know that looking at the dual bounds the objective function of the primal program from below. I know…
aelguindy
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Simplex Method issues solving this problem

I have an exam coming up so I have been going over math questions in my textbook to practice the simplex method. I ran into an issue with questions like this one, and also any that have more constraints then variables. we haven't gone over the DUAL…
Latency
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$Minimize$ $z=-2x-5y$ subject to $3x+4y\ge 5$ , $x\ge 0$ , $y\ge 0$.

Consider the linear programming problem: $Minimize$ $z=-2x-5y$ subject to $3x+4y\ge 5$ , $x\ge 0$ , $y\ge 0$. Which is correct ? (A) Set of feasible solutions is empty. (B) Set of feasible solution is non-empty but there are no optimal solution. (C)…
Empty
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Seating at a large wedding

I have a large wedding of 500 people and 100 tables, each table containing 5 seats. Each person at the wedding lists (up to) 4 people they would like to sit at their table (order of the ranking matters). The more people they sit with, the happier…
afathman
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Linear Programming - How to maximise the maximum

I want to do the following: max: greatest(a1+b1+c1, a2+b2+c2, a3+b3+c3); ... constraints involving a1,a2,a3,b1,b2,b3,c1,c2,c3... Since there is no greatest() function, I restructured it like this: max: greatest_val; greatest_val >=…