sentence-by-sentence.pl.svn-base

解码器是基于短语的统计机器翻译系统的核心模块

{
	my $x = shift;
	return ($x - int($x) < .5) ? int($x) : int($x) + 1;
}

#escape HTML metacharacters for display purposes and to allow for consistent string comparison
#arguments: string to be formatted in place
#return: none
sub escapeMetachars
{
	my $str = shift;
	$str =~ s/&\s+/&amp; /;
	$str =~ s/<\s+/&lt; /;
	$str =~ s/>\s+/&gt; /;
}

###############################################################################################################################################################

#read one line from each of any number of filehandles
#arguments: arrayref of filehandles, (empty) arrayref to be filled with read lines
#return: 1 on success, 0 on failure (on failure the lines arrayref's value isn't defined)
sub readLines
{
	my ($refFilehandles, $refLines) = @_;
	foreach my $fh (@$refFilehandles)
	{
		my $line = <$fh>;
		return 0 unless defined($line);
		push @$refLines, $line;
	}
	return 1;
}

#arguments: line read from corpus file
#return: sentence (arrayref of arrayrefs of factor strings) taken from line
sub extractFactorArrays
{
	my $line = shift;
	die "" if !defined $line;
	chomp $line;
	$line =~ s/^\s*|\s*$//g; #added by Ondrej to handle moses-mert-parallel output
	my @words = split(/\s+/, $line);
	my @factors = map {my @f = split(/\|/, $_); \@f;} @words;
	return \@factors;
}

#can handle multiple reference translations; assume at least one
#arguments: sysout sentence (arrayref of arrayrefs of factor strings), truth sentences (arrayref of same), factor index to use
#return: arrayref of [arrayref of [overall BLEU score, n-gram precisions], arrayref of matching n-gram [start index, length, arrayref of indices of matching references]]
sub getBLEUSentenceDetails
{
	my $maxNgramOrder = 4;
	my ($refSysOutput, $refTruths, $factorIndex) = @_;
	my $length_translation = scalar(@$refSysOutput); #length of sysout sentence
	my @length_references = map {scalar(@$_)} @$refTruths;
	my $closestTruthLength = (sort(map {abs($_ - $length_translation)} @length_references))[0];
	my @correct = (0) x $maxNgramOrder; #n-gram counts
	my @total = (0) x $maxNgramOrder; #n-gram counts
	my $returnData = [[], []];
	my %REF_GRAM; #hash from n-gram to arrayref with # of times found in each reference
	my $ngramMatches = []; #arrayref of n-gram [start index, length]
	for(my $j = 0; $j < scalar(@$refTruths); $j++)
	{
		for(my $i = 0; $i < $length_references[$j]; $i++)
		{
			my $gram = '';
			for(my $k = 0; $k < min($i + 1, $maxNgramOrder); $k++) #run over n-gram orders
			{
				$gram = $refTruths->[$j]->[$i - $k]->[$factorIndex] . " " . $gram;
				#increment the count for the given n-gram and given reference number
				if(!exists $REF_GRAM{$gram})
				{
					my @tmp = (0) x scalar @$refTruths;
					$tmp[$j] = 1;
					$REF_GRAM{$gram} = \@tmp;
				}
				else
				{
					$REF_GRAM{$gram}->[$j]++;
				}
			}
		}
	}
	for(my $i = 0; $i < $length_translation; $i++)
	{
		my $gram = '';
		for(my $k = 0; $k < min($i + 1, $maxNgramOrder); $k++) #run over n-gram orders
		{
			$gram = $refSysOutput->[$i - $k]->[$factorIndex] . " " . $gram;
			if(exists $REF_GRAM{$gram}) #this n-gram was found in at least one reference
			{
				$correct[$k]++;
				my @indices = ();
				my $notOvercounting = 0; #make sure we don't 'match' against truth n-grams whose instances have all been used already
				for(my $m = 0; $m < scalar(@{$REF_GRAM{$gram}}); $m++)
				{
					if($REF_GRAM{$gram}->[$m] > 0)
					{
						push @indices, $m;
						$REF_GRAM{$gram}->[$m]--;
						$notOvercounting = 1;
					}
				}
				if($notOvercounting == 1) {push @$ngramMatches, [$i - $k, $k + 1, \@indices];}
			}
		}
	}
	my $brevity = ($length_translation > $closestTruthLength || $length_translation == 0) ? 1 : exp(1 - $closestTruthLength / $length_translation);
	my @pct;
	my ($logsum, $logcount) = (0, 0);
	for(my $i = 0; $i < $maxNgramOrder; $i++)
	{
		$total[$i] = max(1, $length_translation - $i);
		push @pct, ($total[$i] == 0) ? -1 : $correct[$i] / $total[$i];
		if($total[$i] > 0)
		{
			$logsum += my_log($pct[$i]);
			$logcount++;
		}
	}
	my $bleu = $brevity * exp($logsum / $logcount);
	$returnData->[0] = [$bleu, @pct];
	$returnData->[1] = $ngramMatches;
	return $returnData;
}

#can handle multiple sentence translations; assume at least one
#arguments: sysout sentence (arrayref of arrayrefs of factor strings), truth sentences (arrayref of same), factor index to use
#return: hashref of sysout word index => whether word matches
sub getPWERSentenceDetails
{
	my ($refSysOutput, $refTruths, $factorIndex) = @_;
	my $matches = {};
	my %truthWords; #hash from word to arrayref with number of times seen in each reference (but later holds only the max)
	for(my $i = 0; $i < scalar(@$refTruths); $i++)
	{
		foreach my $eWord (@{$refTruths->[$i]})
		{
			my $factor = $eWord->[$factorIndex];
			if(exists $truthWords{$factor}) {$truthWords{$factor}->[$i]++;}
			else {my @tmp = (0) x scalar(@$refTruths); $tmp[$i] = 1; $truthWords{$factor} = \@tmp;}
		}
	}
	%truthWords = map {$_ => maxN(@{$truthWords{$_}})} (keys %truthWords); #save only the max times each word is seen in a reference
	for(my $j = 0; $j < scalar(@$refSysOutput); $j++)
	{
		if(exists $truthWords{$refSysOutput->[$j]->[$factorIndex]} && $truthWords{$refSysOutput->[$j]->[$factorIndex]} > 0)
		{
			$truthWords{$refSysOutput->[$j]->[$factorIndex]}--;
			$matches->{$j} = 1;
		}
		else
		{
			$matches->{$j} = 0;
		}
	}
	return $matches;
}

#assign ranks to sentences by BLEU score
#arguments: arrayref of arrayrefs of [sentence index, arrayref of [bleu score, n-gram precisions], rank to be assigned]
#return: none
sub rankSentencesByBLEU
{
	my $bleuData = shift;
	my $i = 0;
	#sort first on score, then on 1-gram accuracy, then on sentence index
	foreach my $sentenceData (reverse sort {my $c = $a->[1]->[0] <=> $b->[1]->[0]; if($c == 0) {my $d = $a->[1]->[1] <=> $b->[1]->[1]; if($d == 0) {$a->[0] cmp $b->[0];} else {$d;}} else {$c;}} @$bleuData) {$sentenceData->[2] = $i++;}
}

###############################################################################################################################################################

#write HTML for a sentence containing factors (display words in a row)
#arguments: sentence  (arrayref of arrayrefs of factor strings), PWER results (hashref from word indices to 0/1 whether matched a truth word)
#return: HTML string
sub getFactoredSentenceHTML
{
	my $sentence = shift;
	my $pwer = 0; if(scalar(@_) > 0) {$pwer = shift;}
	my $html = "<table class=\"sentence_table\"><tr>";
	for(my $i = 0; $i < scalar(@$sentence); $i++) #loop over words
	{
		my $style = ''; #default
		if($pwer ne '0' && $pwer->{$i} == 0) {$style = 'color: #cc0000; font-weight: bold';}
		$html .= "<td align=center style=\"$style\">" . join("<br>", @{$sentence->[$i]}) . "</td>";
	}
	return $html . "</tr></table>";
}

#arguments: arrayref of [sentence index, arrayref of [bleu score, n-gram precisions], rank], number of sentences
#return: HTML color string
sub getSentenceBGColorHTML
{
	my ($scoreData, $numSentences) = @_;
	my $tier = int($scoreData->[2] / ($numSentences / scalar(@htmlColors))); #0..n-1
	return $htmlColors[$tier];
}

#display all matching n-grams in the given sentence, with all 1-grams on one line, then arranged by picking, for each, the first line on which it fits,
# where a given word position can only be filled by one n-gram per line, so that all n-grams can be shown
#arguments: sentence (arrayref of arrayrefs of factor strings), arrayref of arrayrefs of matching n-gram [start, length, arrayref of matching reference indices], 
# number of reference translations
#return: HTML string
sub getAllNgramsHTML
{
	my ($sentence, $ngrams, $numTruths) = @_;
	my $factorIndex = 0;
	my @table = (); #array or arrayrefs each of which represents a line; each position has the index of the occupying n-gram, or -1 if none
	my $n = 0; #n-gram index
	foreach my $ngram (sort {$a->[0] <=> $b->[0]} @$ngrams)
	{
		#check for an open slot in an existing row
		my $foundRow = 0;
		my $r = 0;
		foreach my $row (@table)
		{
			if(rowIsClear($row, $ngram) == 1)
			{
				@{$row}[$ngram->[0] .. ($ngram->[0] + $ngram->[1] - 1)] = ($n) x $ngram->[1];
				push @$ngram, $r; #add row index
				$foundRow = 1;
				last;
			}
			$r++;
		}
		#add row if necessary
		if($foundRow == 0)
		{
			my @row = (-1) x scalar(@$sentence);
			@row[$ngram->[0] .. ($ngram->[0] + $ngram->[1] - 1)] = ($n) x $ngram->[1];
			push @$ngram, scalar(@table); #add row index
			push @table, \@row;
		}
		$n++;
	}
	
	my $html = "<table class=\"ngram_table\"><tr><td align=center>" . join("</td><td align=center>", map {$_->[$factorIndex]} @$sentence) . "</td></tr>";
	
	my $numWords = scalar(@$sentence);
	my ($curRow, $curCol) = (0, 0); #address in table
	$html .= "<tr>";
	foreach my $ngram (sort {my $c = $a->[3] <=> $b->[3]; if($c == 0) {$a->[0] <=> $b->[0]} else {$c}} @$ngrams) #sort by row, then word num
	{
		while($ngram->[0] > $curCol || $ngram->[3] > $curRow) {$html .= "<td></td>"; $curCol = ($curCol + 1) % $numWords; if($curCol == 0) {$html .= "</tr><tr>"; $curRow++;}}
		$html .= "<td colspan=" . $ngram->[1] . " align=center class=\"ngram_cell\" style=\"background: " . getNgramColorHTML(scalar(@{$ngram->[2]}), $numTruths) . "\">" . join(' ', map {$_->[$factorIndex]} @{$sentence}[$ngram->[0] .. $ngram->[0] + $ngram->[1] - 1]) . "</td>";
		$curCol = ($curCol + $ngram->[1]) % $numWords; if($curCol == 0) {$html .= "</tr><tr>"; $curRow++;}
	}
	$html .= "</tr>";

	return $html . "</table>\n";
}

#auxiliary to getAllNgramsHTML(): check a table row for an empty piece at the right place for the given n-gram
#arguments: row (arrayref of ints), n-gram (arrayref of [start index, length])
#return: whether (0/1) row is clear
sub rowIsClear
{
	my ($row, $ngram) = @_;
	return (maxN(@{$row}[$ngram->[0] .. $ngram->[0] + $ngram->[1] - 1]) == -1) ? 1 : 0;
}

#auxiliary to getAllNgramsHTML()
#arguments: number of reference translations matching the n-gram, total number of references
#return: HTML color string
sub getNgramColorHTML
{
	my ($matches, $total) = @_;
	if($total == 1) {return $ngramSingleRefColor;}
	return $ngramMultirefColors[round($matches / $total * (scalar(@ngramMultirefColors) - 1))];
}