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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Link between the system matrix and the transportation tableau in the transportation problem

I understand how the method of potentials works (I know the steps) and I can vaguely see its resemblance to revised simplex method. But I just don't have enough intuitive sense about it in order to understand some theory behind it. In particular,…
Koy
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general tips on how to attack linear programming problems

Now for my exam in linear programming I will of course have to be able to translate a given problem into decision variables and an objective value. But my problem is that most of the time I don't know which variables to pick! I find it hard to…
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Linear programming lemma

As part of a review of some famous proofs in Hypergraphs matching I ran into this lemma in Linear programming that I am having difficulty showing (or finding an existing proof online): Let $P=\{\vec{x}\mid A\vec{x}\leq\vec{b}\}$ be the feasible…
eladidan
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Linear Programming - values of x and y yielding maximum values for the following problem:

I found the following linear programming question in a past exam paper while preparing for an upcoming exam: "The daily production of a sweet factory consists of at most 100 kg chocolate covered nuts and at most 125 kg chocolate covered raisins…
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How do I determine that this point is optimal?

I have one linear programming problem given by \begin{matrix}{} \min & \displaystyle\sum_{i=1}^I c_ix_i ; &c_i\geq 0\\ &\\ s.a & \sum_{i=1}^{I}x_i=d,& d\geq0\\ &\\ &0\leq x_i\leq b_i& 1\leq i\leq I …
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Replacing vector in LPP

If we have the following, $$ \text{max: } z = c^Tv $$ $$ \text{s.t } Av = u $$ $$ v \geq 0 $$ If this is unbounded, then can I state that for any vector $u'$ other than $u$ it will either be unbounded or infeasible
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How to reduce the number of iterations in Benders Decomposition for LP?

I am using Benders Decomposition(BD) to solve a linear problem(all decision variables are continuous variables). Though it solved this problem correctly, the number of iterations is up to 315 and it will take too much time. I have searched some…
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Linear programming problem with variables constraints at the R.H.S.

I'd like to analyse the LPP related to parameteres $\mu_i$ at the R.H.S. of the constraints. Specifically, I'd like to determine how the solution to the problem change when the parameters change and what is the range of the parameters where the…
user
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Gomori algorithm: Stuck at second constrain because it gives me the same solution as when I applied the first costrain.

Here is the function to be maximised: $f = x_1 + 2x_2$. Constrains: $$-5x_1+2x_2\le 10 \\ 3x_1+2x_2\le12 \\ x_1-4x_2\le 3$$ I need to find a solution to this problem with $x_1,x_2 \in Z$ using Gomori algorithm. First I applied simplex algorithm to…
user
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Finding a lower bound for a linear program given a feasible solution and the minimal reduced cost

I'm struggling a bit with my understanding of reduced cost in linear programs. I know how they are calculated and understand why and know that they tell us how much the objective function improves when we increase the value of the corresponding…
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Maximum value(LPP)

Let $\alpha \in R $ . If $(3,0,0,\beta)$ is an optimal solution of LPP, Minimize $x+y+z-\alpha t$ s.t $ 2x-y+z=6$ $-x+y+t=3$ $x,y,z,t \ge 0 $ The the maximum value of $\beta - \alpha$ is ? My attempt: I tried by simply plugging in the value of…
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Determination of a saddle point of function $E(p,q)$ as a Linear Programming Problem.

Suppose that all payoff matrix $A$ elements are non negative and that each column and each row contains at leat one positive element. To find each opponents optimal mixed strategy, a Linear Programming problem is used: $$f = \sum^k_{j=1}z_j…
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Doubts in a textbook lemma

There is a lemma in the book saying: "If the primal basic solution is an optimal solution of a linear program (P), B is not necessarily an optimal basis." I don't understand because, by the dual theory, if the primal has a feasible solution and so…
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Why are basic feasible solutions extremes of the feasible set?

Consider a linear system $\newcommand{\vv}{\mathbf{v}}\newcommand{\xx}{\mathbf{x}}\newcommand{\bb}{\mathbf{b}}A\xx=\bb$ with $\xx\in\mathbb R^m$, $\mathbf b\in\mathbb R^n$, and suppose $\operatorname{rank}(A)=n$. We then say that $\xx_B\in\mathbb…
glS
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Finding the number of basic/zero variables at an optimal corner point in linear programming

Draw a graph of the following problem $$\begin{align}4x+3y &\leq 180 \\ 7x+4y &\leq 280 \\ y &\leq 40 \\ x &\geq 0 \\ y &\geq 0\end{align}$$ a) If the problem is to maximize the objective function $z= 5x+6y$ subject to above constrains, what…
Zack
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