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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Rewrite the feasible set of a linear programming problem

Consider a $K\times 1$ vector $x$ and define $$ \mathcal{X}\equiv\{x\in \mathbb{R}^K: A*x\leq b\} $$ where $A$ is a $J\times K$ matrix containing known real scalars and $b$ is a $J\times 1$ vector containing known real scalars. Is it correct to say…
Star
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Determine whether an optimization problem is a linear program

Can anyone help me with the following problem? Consider an optimization problem (P) that has two variables $x_1$ and $x_2$. Here are the following facts of P: $x_1 = 3, x_2 = 6$ is a feasible solution. $x_1 = 5, x_2 = 2$ is a feasible…
user720998
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Coefficients of a simplex linear program are all zero

I have the following linear program that keeps evaluating all solutions to zero. Which additional constraints could I add to force $x>0$ or $y>0$ or both $z,y>0$? \begin{equation*} \begin{aligned} & \underset{f}{\text{min}} & & f(x,y,z) = 0.23x +…
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What is linear constraint?

Is linear constraint a constraint in form of linear equation? I used equation $f_i(\alpha x + \beta y) = \alpha f_i(x) + \beta f_i(y)$ to test linearity of constraint . For $f_i(x) =x+5$ test failed. For $f_i(x) =2x$ test passed. What I don't get…
BRUCE
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Linear Program Feasible

Consider the LP: $ \max 0^T x\\ \mbox{subject to } Ax \leq b\\ $ Is this LP feasible or infeasible? I am unsure since I cannot prove it is infeasible although the objective value is always going to be $0$? Can anyone help me out?
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Linear Programming (Approach)

A chemical manufacturer manufactures 2 types of chemical, A and B. Manager informs that the company has a maximum of 504 manpower hours in a week while having a minimum of 5000 litres of ingredient X. A and B contribute to 60% and 40% of the total…
Mathxx
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How to bring $\sum_{i=1}^n \lvert x_i \rvert$ with $Ax=b$ in canonical form

I am working on the following exercise: Bring the LP $$\min \sum_{i=1}^n \lvert x_i \rvert \text{ with } Ax=b$$ in canonical form $$\min \sum_{i=1}^n c_i x_i \text{ with } Ax=b, x \ge 0.$$ My attempt thus far goes as follows: To get rid of the…
3nondatur
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Linear Programming problem - Proportion

A farmer can purchase 3 kinds of feed for his stock, with various percentages of each of 4 nutrients, called A, B, C, and D. A mixture of feeds gives proportional amounts of nutrients. The following table gives the minimum daily requirements (lb),…
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0-1 linear programming vs mixed integer linear programming problems

I wonder whether or not it is possible to say which one is to be preferred when it comes to complexity, since as far as I know both methods are known to be NP-complete. When you have the choice between formulating a problem as mixed integer problem…
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How to solve a linear programming question with an "average" constraint

I'm trying to solve the question below: "An $8$ year old child usually has $24$ teeth. A dental researcher has estimated that on an average, $8$ year old kids in a geographical region have $1.8$ decayed teeth each. Give LP formulations for the…
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points beneath a line equation

In Linear Programming say in $R^2$ if you have a factory that can produce 2 products P1 and P2 and if 100% for P1 then it can produce 15 or 100% P2 it can produce 12 and assuming a linear relationship, often we are asked to find the convex set of…
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What are the constraints on this system

A company produces 2 types of frames, an ATB frame and a race frame For the ATB frama you need 4kg of aluminum and 6kg of steel, for the race from you need 5kg of aluminum and 2kg of steel. They sell the ATB frames for 1960 euros a piece and the…
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Linear programming - Standard form with variable restricted from both sides

I have a pretty straightforward linear programming problem here: $$ maximize \hskip 5mm -x_1 + 2x_2 -3x_3 $$ subject to $$ 5x_1 - 6x_2 - 2x_3 \leq 2 $$ $$ 5x_1 - 2x_3 = 6 $$ $$ x_1 - 3x_2 + 5x_3 \geq -3 $$ $$ 1 \leq x_1 \leq 4 $$ $$ x_3 \leq 3…
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Linear programming such that feasible solution gives optimal solution to another

Let us say that we have a linear program $P=\{ \min C^tx \mid Ax=b,x\geq0\}$ Assume that $(P)$ has an optimal solution. Write a system of linear equations and inequalities $(P_1)$ such that any feasible solution to $(P_1)$ gives us an optimal…
onlymath
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How to show that the lpp has optimal solution without solving it

I have got to maximize $$Z=x+2y-3z+4w$$ subject to constraints $$x+y+2z+3w=12$$ $$y+2z+w=8$$ $x,y,z,w\geq 0$ . The question asks to show without actually solving the lpp that it has an optimal solution. For that I added the…