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#!/usr/bin/perl -w
use utf8;
# (c) 2006-2010 Felipe Sánchez Martínez
# (c) 2006-2010 Universitat d'Alacant
#
# This software calculates the word error rate (WER) between an
# automatic translation and a reference translation.
#
# The edit_distance procedure used in this script is based on
# the Levenshtein distance implementation by Jorge Mas Trullenque
# that can be found in http://www.mgilleland.com/ld/ldperl2.htm
#
# This software is licensed under the GPL license version 3, or at
# your option any later version
use strict;
use warnings;
# Getting command line arguments:
use Getopt::Long;
# Documentation:
use Pod::Usage;
# I/O Handler
use IO::Handle;
my($test, $ref, $help, $seg, $version);
# Command line arguments
GetOptions( 'test|t=s' => \$test,
'ref|r=s' => \$ref,
'seg|s' => \$seg,
'help|h' => \$help,
'version|v' => \$version,
) || pod2usage(2);
if ($version) {
print "WER.pl 1.0\n";
exit 0;
}
pod2usage(2) if $help;
pod2usage(2) unless ($test);
pod2usage(2) unless ($ref);
open(TEST, "<$test") or die "Error: Cannot open test file \'$test\': $!\n";
open(REF, "<$ref") or die "Error: Cannot open reference file \'$ref\': $!\n";
my($ntest, $nref, $distance) = (0, 0, 0);
my(@words_test, @words_ref);
my $line = 0;
while(<TEST>) {
chomp;
s/^\s+//g;
s/\s+$//g;
@words_test = split /\s+/;
$_=<REF>;
chomp;
s/^\s+//g;
s/\s+$//g;
@words_ref = split /\s+/;
$line++;
my $this_distance = &edit_distance;
print "LINE $line ", $this_distance/@words_ref, "\n" if ($seg);
$distance += $this_distance;
$ntest += @words_test;
$nref += @words_ref;
}
close(TEST);
close(REF);
print $distance/$nref, "\n";
sub edit_distance {
my @W=(0..@words_ref);
my ($i, $j, $cur, $next);
return scalar(@words_ref) if (scalar(@words_test) == 0);
return scalar(@words_test) if (scalar(@words_ref) == 0);
for $i (0..$#words_test) {
$cur=$i+1;
for $j (0..$#words_ref){
my $cost=($words_test[$i] ne $words_ref[$j]);
$next=min($W[$j+1]+1, $cur+1, $cost+$W[$j]);
$W[$j]=$cur;
$cur=$next;
}
$W[@words_ref]=$next;
}
return $next;
}
sub min {
my @list = @_;
my $min = $list[0];
foreach my $i (@list) {
$min = $i if ($i < $min);
}
return $min;
}
__END__
=head1 NAME
=head1 SYNOPSIS
WER.pl -test testfile -ref reffile
Options:
-test|-t Specify the file with the translation to evaluate
-ref|-r Specify the file with the reference translation (only one)
-seg|-s Report WER also at segment level
-help|-h Show this help message
-version|-v Show version information and exit
This software calculates (at segment level and document level)
the word error rate (WER) between an automatic translation
and a reference translation.
(c) 2006-2010 Felipe Sánchez-Martínez
(c) 2006-2010 Universitat d'Alacant
This software is licensed under the GNU GENERAL PUBLIC LICENSE version
3, or at your option any latter version. See
http://www.gnu.org/copyleft/gpl.html for a complete version of the
license.
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