Commit 3f5b1976 authored by msurl's avatar msurl
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added first draft of introduction to ilp

parent b976f0b2
\section{Linear Programming} \raggedbottom
Linear programming is a technique to minimize linear functions.
A linear programm (LP) consists of a objective function, which is minimized with respect to a set of linear inequalities. \\
Linear programms can be expressed as
\[min\{c^Tx : Ax \geq b, x \geq 0\}\]
$b \in \mathbb{R}^n$ and $c \in \mathbb{R}^n$ are constant vectors. $Ax \leq b$ denotes the inequalities which have to be respected. $A \in \mathbb{R}^{m \times n}$ is a matrix containing the coefficients of the $m$ inequalities. $c^Tx \in R$ is the objective function which is minimized.
$x \in \mathbb{R}$ is a vector describing possible solutions. If $x \in \mathbb{R}$ obeys all inequalities it is called a feasible solution. A solution $x^*$ is optimal if respects all inequalities and is minimal.
Integer linear programms (ILPs) are linear programms with the additional restriction that all variables have to be integers: $x \in \mathbb{Z}$.
The decision variant of an ILP is NP-complete.
In this thesis we use a more readable notation which does not completely sticks to this definition. We write down the inequalities in a sum notation. (Maybe an example?) But it is possible to transform them into the matrix notation.
Decision problems can be modelles with ILPs. Every variable $x_i \in \{0,1\}$ denotes a possible decision. In our case we assign a decision variable for each vertex to decide if it is included in a dominating set or not.
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