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#!/usr/bin/perl -w
# $Id$
use strict;
my $lowercase = 0;
if ($ARGV[0] eq "-lc") {
$lowercase = 1;
shift;
}
my $stem = $ARGV[0];
if (!defined $stem) {
print STDERR "usage: multi-bleu.pl [-lc] reference < hypothesis\n";
print STDERR "Reads the references from reference or reference0, reference1, ...\n";
exit(1);
}
$stem .= ".ref" if !-e $stem && !-e $stem."0" && -e $stem.".ref0";
my @REF;
my $ref=0;
while(-e "$stem$ref") {
&add_to_ref("$stem$ref",\@REF);
$ref++;
}
&add_to_ref($stem,\@REF) if -e $stem;
die("ERROR: could not find reference file $stem") unless scalar @REF;
sub add_to_ref {
my ($file,$REF) = @_;
my $s=0;
open(REF,$file) or die "Can't read $file";
while(<REF>) {
chop;
push @{$$REF[$s++]}, $_;
}
close(REF);
}
my(@CORRECT,@TOTAL,$length_translation,$length_reference);
my $s=0;
while(<STDIN>) {
chop;
$_ = lc if $lowercase;
my @WORD = split;
my %REF_NGRAM = ();
my $length_translation_this_sentence = scalar(@WORD);
my ($closest_diff,$closest_length) = (9999,9999);
foreach my $reference (@{$REF[$s]}) {
# print "$s $_ <=> $reference\n";
$reference = lc($reference) if $lowercase;
my @WORD = split(' ',$reference);
my $length = scalar(@WORD);
my $diff = abs($length_translation_this_sentence-$length);
if ($diff < $closest_diff) {
$closest_diff = $diff;
$closest_length = $length;
# print STDERR "$s: closest diff ".abs($length_translation_this_sentence-$length)." = abs($length_translation_this_sentence-$length), setting len: $closest_length\n";
} elsif ($diff == $closest_diff) {
$closest_length = $length if $length < $closest_length;
# from two references with the same closeness to me
# take the *shorter* into account, not the "first" one.
}
for(my $n=1;$n<=4;$n++) {
my %REF_NGRAM_N = ();
for(my $start=0;$start<=$#WORD-($n-1);$start++) {
my $ngram = "$n";
for(my $w=0;$w<$n;$w++) {
$ngram .= " ".$WORD[$start+$w];
}
$REF_NGRAM_N{$ngram}++;
}
foreach my $ngram (keys %REF_NGRAM_N) {
if (!defined($REF_NGRAM{$ngram}) ||
$REF_NGRAM{$ngram} < $REF_NGRAM_N{$ngram}) {
$REF_NGRAM{$ngram} = $REF_NGRAM_N{$ngram};
# print "$i: REF_NGRAM{$ngram} = $REF_NGRAM{$ngram}<BR>\n";
}
}
}
}
$length_translation += $length_translation_this_sentence;
$length_reference += $closest_length;
for(my $n=1;$n<=4;$n++) {
my %T_NGRAM = ();
for(my $start=0;$start<=$#WORD-($n-1);$start++) {
my $ngram = "$n";
for(my $w=0;$w<$n;$w++) {
$ngram .= " ".$WORD[$start+$w];
}
$T_NGRAM{$ngram}++;
}
foreach my $ngram (keys %T_NGRAM) {
$ngram =~ /^(\d+) /;
my $n = $1;
# my $corr = 0;
# print "$i e $ngram $T_NGRAM{$ngram}<BR>\n";
$TOTAL[$n] += $T_NGRAM{$ngram};
if (defined($REF_NGRAM{$ngram})) {
if ($REF_NGRAM{$ngram} >= $T_NGRAM{$ngram}) {
$CORRECT[$n] += $T_NGRAM{$ngram};
# $corr = $T_NGRAM{$ngram};
# print "$i e correct1 $T_NGRAM{$ngram}<BR>\n";
}
else {
$CORRECT[$n] += $REF_NGRAM{$ngram};
# $corr = $REF_NGRAM{$ngram};
# print "$i e correct2 $REF_NGRAM{$ngram}<BR>\n";
}
}
# $REF_NGRAM{$ngram} = 0 if !defined $REF_NGRAM{$ngram};
# print STDERR "$ngram: {$s, $REF_NGRAM{$ngram}, $T_NGRAM{$ngram}, $corr}\n"
}
}
$s++;
}
my $brevity_penalty = 1;
my $bleu = 0;
my @bleu=();
for(my $n=1;$n<=4;$n++) {
if (defined ($TOTAL[$n])){
$bleu[$n]=($TOTAL[$n])?$CORRECT[$n]/$TOTAL[$n]:0;
# print STDERR "CORRECT[$n]:$CORRECT[$n] TOTAL[$n]:$TOTAL[$n]\n";
}else{
$bleu[$n]=0;
}
}
if ($length_reference==0){
printf "BLEU = 0, 0/0/0/0 (BP=0, ratio=0, hyp_len=0, ref_len=0)\n";
exit(1);
}
if ($length_translation<$length_reference) {
$brevity_penalty = exp(1-$length_reference/$length_translation);
}
$bleu = $brevity_penalty * exp((my_log( $bleu[1] ) +
my_log( $bleu[2] ) +
my_log( $bleu[3] ) +
my_log( $bleu[4] ) ) / 4) ;
printf "BLEU = %.2f, %.1f/%.1f/%.1f/%.1f (BP=%.3f, ratio=%.3f, hyp_len=%d, ref_len=%d)\n",
100*$bleu,
100*$bleu[1],
100*$bleu[2],
100*$bleu[3],
100*$bleu[4],
$brevity_penalty,
$length_translation / $length_reference,
$length_translation,
$length_reference;
sub my_log {
return -9999999999 unless $_[0];
return log($_[0]);
}
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