# gfprimfd

Find primitive polynomials for Galois field

## Syntax

`pol = gfprimfd(m,`

* opt*,p)

## Description

**Note**

This function performs computations in GF(p^{m}), where
p is prime. To work in GF(2^{m}), use the
`primpoly`

function. For details, see *Finding
Primitive Polynomials* in Primitive Polynomials and Element Representations.

If

`m`

= 1,`pol`

= [1 1].A polynomial is represented as a row containing the coefficients in order of ascending powers.

`pol = gfprimfd(m,`

searches
for one or more primitive polynomials for GF(* opt*,p)

`p^m`

),
where `p`

is a prime number and `m`

is
a positive integer. If `m`

= 1, `pol`

= [1
1]. If `m `

> 1,
the output `pol`

depends on the argument *as shown in the table below. Each polynomial is represented in*

`opt`

`pol`

as
a row containing the coefficients in order of ascending powers. opt | Significance of pol | Format of pol |
---|---|---|

`'min'` | One primitive polynomial
for GF(`p^m` ) having the smallest possible number
of nonzero terms | The row vector representing the polynomial |

`'max'` | One primitive polynomial
for GF(`p^m` ) having the greatest possible number
of nonzero terms | The row vector representing the polynomial |

`'all'` | All primitive polynomials
for GF(`p^m` ) | A matrix, each row of which represents one such polynomial |

A positive integer | All primitive polynomials
for GF(`p^m` ) that have nonzero
terms `opt` | A matrix, each row of which represents one such polynomial |

## Examples

The code below seeks primitive polynomials for GF(81) having
various other properties. Notice that `fourterms`

is
empty because no primitive polynomial for GF(81) has exactly four
nonzero terms. Also notice that `fewterms`

represents
a *single* polynomial having three terms, while `threeterms`

represents *all* of
the three-term primitive polynomials for GF(81).

p = 3; m = 4; % Work in GF(81). fewterms = gfprimfd(m,'min',p) threeterms = gfprimfd(m,3,p) fourterms = gfprimfd(m,4,p)

The output is below.

fewterms = 2 1 0 0 1 threeterms = 2 1 0 0 1 2 2 0 0 1 2 0 0 1 1 2 0 0 2 1 No primitive polynomial satisfies the given constraints. fourterms = []

## Algorithms

`gfprimfd`

tests for primitivity using `gfprimck`

. If * opt* is

`'min'`

, `'max'`

, or omitted, polynomials are
constructed by converting decimal integers to base `p`

. Based on the
decimal ordering, `gfprimfd`

returns the first polynomial it finds
that satisfies the appropriate conditions.## Version History

**Introduced before R2006a**