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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Linear Programming Problem About Inventory and Cost Minimizing

http://www.endustri.anadolu.edu.tr/zkamisli/ENM%20203/duyuru/ENM203%20Assignment%202.pdf In that link, you can find my question. I'm having trouble about defining decision variables. The objective function must minimize the cost of 6-months…
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problem related to duality theorem in linear programming

Theorem $$\max\{c^Tx:x\ge0;Ax\le b\} = \min\{y^Tb:y\ge0;y^TA\ge c^T\}$$ (assuming both sets are nonempty) Use the above theorem to prove the following variant of the duality theorem: $$\max\{c^Tx:Ax=b;x\le0\} = \min\{y^Tb:y^TA\le…
Tom
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Linear Program height and diameter.

In page 3 of this paper on linear programming, they define $L(d,n)$ to be the set of linear program with $d$ variables and $n$ constraints. They also define a linear objective function $\phi$. For a linear programming problem $O \in L(d,n)$, $P$ is…
plops
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Testing if Linear Programming System Implies Another System

Is there a method for testing if one system of linear inequalities implies another one? For example, consider systems A and B: A: x + y <= z B: x <= z y <= z If all variables are constrained to be non-negative (typical in LP), then intuition…
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Cubic Polynomial Linearisation

I have a cubic polynomial defined as below which needs to be linearised as a constraint for an MIP model in Gurobipy. I have seen a couple different methods including using the Gurobi general constraint for polynomial. However, using that method…
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What does splitting a variable mean in a postive/negative part?

I am currently studying linear programming and came across a specific problem that involves substitution and variable conversion. Although I have consulted relevant resources, I am still a bit confused about a few aspects. I would greatly appreciate…
Tim
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A linear programming problem, any textbook name or hint will be appreciated

Let $a_1, a_2,a_3,a_4,d \in \mathbb{R}$ that $$a_3 < a_1 + d < a_4$$, $$a_1 < a_4 - d < a_2$$, $$a_1 < a_2 < a_3 < a_4$$ I tried to manipulate these inequalities to get some result. But I didn't find anything useful. How to find the minimum and…
yuanming luo
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Linear Programming: how to write dual problem with slack variables

Lets say I have this primal problem: maximize $z = 6x_1 + 10x_2$ subject to: $2x_1+8x_2\leq 60$ $3x_1+5x_2\leq45$ $x_1, x_2 \geq 0$ With slack variables in matrix notation ($Ax=b$) I get: $A =\begin{pmatrix} 2 & 8 & 1 & 0\\ 3 & 5 & 0 &…
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possible to index a set by a variable?

I am trying to do something that logically should be possible to do. However, I am not sure how to do this within the realm of linear programming. I am using ZMPL/SCIP, but this should be readable to most. set I := {1,2,3,4,5}; param u[I] := <1>…
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How to graph an interval of real numbers?

Assume that intergers $m$ and $n$ satisfy $2|m|+3|n-1|\leq 7$. $m+n$ is maximum when $(m,n) = (3,?), (?,?)$ and its maximum value is $?$ given the above question the first thing i tried was calculating the intervals for each variable like…
Carlos
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Elementary proof of sum of largest components in a vector equals a Linear program

For $n,k \in \mathbb{N}$ with $k \leq n$ let $f_k: \mathbb{R}^n \to \mathbb{R}$ be the following function $$ f_k(x) := \sum_{i=1}^k x_{[i]}, $$ where $x_{[i]}$ is the $i$-th largest component of $x \in \mathbb{R}^n$. I know that $f_k(x)$ equals the…
wayne
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Why do the penalties of the Vogel method work?

Vogel's method selects the corresponding variable through a penalty. There is a penalty for each row and column and is the subtraction between the two lowest costs (in absolute value). We must select the highest penalty and then the lowest cost in…
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An if and only if implication for a linear program to have a bounded optimum objective value

I am new to linear programming. I came across a problem which seems easy but I am failing to figure out how to prove it. Suppose the following LP is feasible: $\text{max}$ $c^Tx$ $\text{s.t. }$ $Ax\leq b.$ Prove that the optimum objective value of…
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Linear program, entering/leaving variables & exit conditions

I'm trying to implement my own Simplex solver and I'm encountering some issues. When choosing the leaving variable, one is supposed to pick the element with the smallest positive $b_i/x_{i,j}$ where $j$ is the entering column chosen earlier. Are…
Chris
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Dual problem for linear programming

I tried to solve this problem, but I am not sure if I am right. Otherwise, I find some solution in one book and solution is very questionable. One more thing, I am not sure how to this problems when there are equality constraints. Find dual problem…
Broj 1
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