CGAL 4.12.1 - Linear and Quadratic Programming Solver
LinearProgram Concept Reference

## Definition

A model of LinearProgram describes a linear program of the form.

$$\newcommand{\qprel}{\gtreqless} \newcommand{\qpx}{\mathbf{x}} \newcommand{\qpl}{\mathbf{l}} \newcommand{\qpu}{\mathbf{u}} \newcommand{\qpc}{\mathbf{c}} \newcommand{\qpb}{\mathbf{b}} \newcommand{\qpy}{\mathbf{y}} \newcommand{\qpw}{\mathbf{w}} \newcommand{\qplambda}{\mathbf{\lambda}}$$

\begin{eqnarray*} \mbox{(QP)}& \mbox{minimize} & \qpc^{T}\qpx+c_0 \\ &\mbox{subject to} & A\qpx\qprel \qpb, \\ & & \qpl \leq \qpx \leq \qpu \end{eqnarray*}

in $$n$$ real variables $$\qpx=(x_0,\ldots,x_{n-1})$$. Here,

• $$A$$ is an $$m\times n$$ matrix (the constraint matrix),
• $$\qpb$$ is an $$m$$-dimensional vector (the right-hand side),
• $$\qprel$$ is an $$m$$-dimensional vector of relations from $$\{\leq, =, \geq\}$$,

• $$\qpl$$ is an $$n$$-dimensional vector of lower bounds for $$\qpx$$, where $$l_j\in\mathbb{R}\cup\{-\infty\}$$ for all $$j$$
• $$\qpu$$ is an $$n$$-dimensional vector of upper bounds for $$\qpx$$, where $$u_j\in\mathbb{R}\cup\{\infty\}$$ for all $$j$$

• $$\qpc$$ is an $$n$$-dimensional vector (the linear objective function), and
• $$c_0$$ is a constant.

The description is given by appropriate random-access iterators over the program data, see below. The program therefore comes in dense representation which includes zero entries.

Has Models:

CGAL::Linear_program_from_iterators<A_it, B_it, R_it, FL_it, L_it, FU_it, U_it, D_it, C_it>

and the other concepts

NonnegativeLinearProgram

## Types

typedef unspecified_type A_iterator
A random access iterator type to go columnwise over the constraint matrix $$A$$. More...

typedef unspecified_type B_iterator
A random access iterator type to go over the entries of the right-hand side $$\qpb$$.

typedef unspecified_type R_iterator
A random access iterator type to go over the relations $$\qprel$$. More...

typedef unspecified_type FL_iterator
A random access iterator type to go over the existence (finiteness) of the lower bounds $$l_j, j=0,\ldots,n-1$$. More...

typedef unspecified_type L_iterator
A random acess iterator type to go over the entries of the lower bound vector $$\qpl$$.

typedef unspecified_type UL_iterator
A random access iterator type to go over the existence (finiteness) of the upper bounds $$u_j, j=0,\ldots,n-1$$. More...

typedef unspecified_type U_iterator
A random acess iterator type to go over the entries of the upper bound vector $$\qpu$$.

typedef unspecified_type C_iterator
A random access iterator type to go over the entries of the linear objective function vector $$c$$.

## Operations

int get_n () const
returns the number $$n$$ of variables (number of columns of $$A$$) in lp.

int get_m () const
returns the number $$m$$ of constraints (number of rows of $$A$$) in lp.

A_iterator get_a () const
returns an iterator over the columns of $$A$$. More...

B_iterator get_b () const
returns an iterator over the entries of $$\qpb$$. More...

R_iterator get_r () const
returns an iterator over the entries of $$\qprel$$. More...

FL_iterator get_fl () const
returns an iterator over the existence of the lower bounds $$l_j, j=0,\ldots,n-1$$. More...

L_iterator get_l () const
returns an iterator over the entries of $$\qpl$$. More...

FU_iterator get_fu () const
returns an iterator over the existence of the upper bounds $$u_j, j=0,\ldots,n-1$$. More...

L_iterator get_u () const
returns an iterator over the entries of $$\qpu$$. More...

C_iterator get_c () const
returns an iterator over the entries of $$\qpc$$. More...

std::iterator_traits< C_iterator >::value_type get_c0 () const
returns the constant term $$c_0$$ of the objective function.

## ◆ A_iterator

A random access iterator type to go columnwise over the constraint matrix $$A$$.

The value type is a random access iterator type for an individual column that goes over the entries in that column.

## ◆ FL_iterator

A random access iterator type to go over the existence (finiteness) of the lower bounds $$l_j, j=0,\ldots,n-1$$.

The value type of FL_iterator is bool.

## ◆ R_iterator

A random access iterator type to go over the relations $$\qprel$$.

The value type of R_iterator is CGAL::Comparison_result.

## ◆ UL_iterator

A random access iterator type to go over the existence (finiteness) of the upper bounds $$u_j, j=0,\ldots,n-1$$.

The value type of UL_iterator is bool.

## ◆ get_a()

 A_iterator LinearProgram::get_a ( ) const

returns an iterator over the columns of $$A$$.

The corresponding past-the-end iterator is get_a()+get_n(). For $$j=0,\ldots,n-1$$, *(get_a()+j) is a random access iterator for column $$j$$.

## ◆ get_b()

 B_iterator LinearProgram::get_b ( ) const

returns an iterator over the entries of $$\qpb$$.

The corresponding past-the-end iterator is get_b()+get_m().

## ◆ get_c()

 C_iterator LinearProgram::get_c ( ) const

returns an iterator over the entries of $$\qpc$$.

The corresponding past-the-end iterator is get_c()+get_n().

## ◆ get_fl()

 FL_iterator LinearProgram::get_fl ( ) const

returns an iterator over the existence of the lower bounds $$l_j, j=0,\ldots,n-1$$.

The corresponding past-the-end iterator is get_fl()+get_n(). If *(get_fl()+j) has value $$true$$, the variable $$x_j$$ has a lower bound given by *(get_l()+j), otherwise it has no lower bound.

## ◆ get_fu()

 FU_iterator LinearProgram::get_fu ( ) const

returns an iterator over the existence of the upper bounds $$u_j, j=0,\ldots,n-1$$.

The corresponding past-the-end iterator is get_fu()+get_n(). If *(get_fu()+j) has value $$true$$, the variable $$x_j$$ has an upper bound given by *(get_u()+j), otherwise it has no upper bound.

## ◆ get_l()

 L_iterator LinearProgram::get_l ( ) const

returns an iterator over the entries of $$\qpl$$.

The corresponding past-the-end iterator is get_l()+get_n(). If *(get_fl()+j) has value $$false$$, the value *(get_l()+j) is not accessed.

Precondition
if both *(get_fl()+j) and *(get_fu()+j) have value $$true$$, then *(get_l()+j) <= *(get_u()+j).

## ◆ get_r()

 R_iterator LinearProgram::get_r ( ) const

returns an iterator over the entries of $$\qprel$$.

The corresponding past-the-end iterator is get_r()+get_m(). The value CGAL::SMALLER stands for $$\leq$$, CGAL::EQUAL stands for $$=$$, and CGAL::LARGER stands for $$\geq$$.

## ◆ get_u()

 L_iterator LinearProgram::get_u ( ) const

returns an iterator over the entries of $$\qpu$$.

The corresponding past-the-end iterator is get_u()+get_n(). If *(get_fu()+j) has value $$false$$, the value *(get_u()+j) is not accessed.

Precondition
if both *(get_fl()+j) and *(get_fu()+j) have value $$true$$, then *(get_l()+j) <= *(get_u()+j).