perl-scripts/Math/matrix_determinant_bareiss.pl at master · trizen/perl-scripts · GitHub

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#!/usr/bin/perl

# Daniel "Trizen" Șuteu

# License: GPLv3

# Date: 20 November 2016

# https://github.com/trizen

# The Bareiss algorithm for computing the determinant of a (square) matrix.

# Algorithm from:

# https://apidock.com/ruby/v1_9_3_125/Matrix/determinant_bareiss

# See also:

# https://en.wikipedia.org/wiki/Bareiss_algorithm

use 5.010;

use strict;

use warnings;

use List::Util qw(first);

sub det {

my ($m) = @_;

my @m = map { [@$_] } @$m;

my $sign = +1;

my $pivot = 1;

my $end = $#m;

foreach my $k (0 .. $end) {

my @r = ($k + 1 .. $end);

my $prev_pivot = $pivot;

$pivot = $m[$k][$k];

if ($pivot == 0) {

my $i = (first { $m[$_][$k] } @r) // return 0;

@m[$i, $k] = @m[$k, $i];

$pivot = $m[$k][$k];

$sign = -$sign;

}

foreach my $i (@r) {

foreach my $j (@r) {

(($m[$i][$j] *= $pivot) -= $m[$i][$k] * $m[$k][$j]) /= $prev_pivot;

}

$sign * $pivot;

}

my $matrix = [

[2, -1, 5, 1],

[3, 2, 2, -6],

[1, 3, 3, -1],

[5, -2, -3, 3],

];

say det($matrix); #=> 684

perl-scripts/Math/matrix_determinant_bareiss.pl at master · trizen/perl-scripts · GitHub

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