corpus.pm.svn-base

解码器是基于短语的统计机器翻译系统的核心模块

	#calculate first two moments for subset scores for each n-gram precision, and t statistic
	my $fullCorpusBLEU = $self->{'bleuScores'}->{$sysname}->{$factorName}->[0]; #an arrayref
	my @means = (0) x 4;
	my @devs = (0) x 4;
	my $t = []; #t statistics for all n-gram orders
	if(!exists $self->{'bleuConfidence'}->{$sysname}) {$self->{'bleuConfidence'}->{$sysname} = {};}
	$self->{'bleuConfidence'}->{$sysname}->{$factorName} = [[], []]; #lower-bound p-values for whole corpus vs. subset average; confidence intervals for all n-gram orders
	for(my $i = 0; $i < 4; $i++) #run through n-gram orders
	{
		for(my $j = 0; $j < $k; $j++) #run through subsets
		{
			$means[$i] += $subsetStats->[$j]->[2 * $i] / $subsetStats->[$j]->[2 * $i + 1]; #matching / total n-grams
		}
		$means[$i] /= $k;
		for(my $j = 0; $j < $k; $j++) #run through subsets
		{
			$devs[$i] += ($subsetStats->[$j]->[2 * $i] / $subsetStats->[$j]->[2 * $i + 1] - $means[$i]) ** 2;
		}
		$devs[$i] = sqrt($devs[$i] / ($k - 1));
		$t->[$i] = ($fullCorpusBLEU->[$i + 1] / 100 - $means[$i]) / $devs[$i];
		push @{$self->{'bleuConfidence'}->{$sysname}->{$factorName}->[0]}, getLowerBoundPValue($t->[$i]); #p-value for overall score vs. subset average
		push @{$self->{'bleuConfidence'}->{$sysname}->{$factorName}->[1]}, 
							[$means[$i] - $criticalTStat * $devs[$i] / sqrt($k), $means[$i] + $criticalTStat * $devs[$i] / sqrt($k)]; #the confidence interval
	}
	
	return $self->{'bleuConfidence'}->{$sysname}->{$factorName};
}

#arguments: system name, factor name
#return: perplexity of language model (specified in a config file) wrt given system output
sub calcPerplexity
{
	my ($self, $sysname, $factorName) = @_;
	print STDERR "ppl $sysname $factorName\n";
	#check in-memory cache first
	if(exists $self->{'perplexity'}->{$sysname} && exists $self->{'perplexity'}->{$sysname}->{$factorName})
	{
		return $self->{'perplexity'}->{$sysname}->{$factorName};
	}
	warn "calcing perplexity\n";
	
	$self->ensureFilenameDefined($sysname);
	my $sysoutFilename;
	if($sysname eq 'truth' || $sysname eq 'input') {$sysoutFilename = $self->{"${sysname}Filename"};}
	else {$sysoutFilename = $self->{'sysoutFilenames'}->{$sysname};}
	my $lmFilename;
	if($sysname eq 'input') {$lmFilename = $self->{'inputLMs'}->{$factorName};}
	else {$lmFilename = $self->{'outputLMs'}->{$factorName};}
	my $tmpfile = ".tmp" . time;
	my $cmd = "perl ./extract-factors.pl $sysoutFilename " . $self->{'factorIndices'}->{$factorName} . " > $tmpfile";
	`$cmd`; #extract just the factor we're interested in; ngram doesn't understand factored notation
	my @output = `./ngram -lm $lmFilename -ppl $tmpfile`; #run the SRI n-gram tool
	`rm -f $tmpfile`;
	$output[1] =~ /ppl1=\s*([0-9\.]+)/;
	$self->{'perplexity'}->{$sysname}->{$factorName} = $1;
	return $self->{'perplexity'}->{$sysname}->{$factorName};
}

#run a paired t test and a sign test on BLEU statistics for subsets of both systems' outputs
#arguments: system name 1, system name 2, factor name
#return: arrayref of [arrayref of confidence levels for t test at which results differ, arrayref of index (0/1) of better system by t test,
#                     arrayref of confidence levels for sign test at which results differ, arrayref of index (0/1) of better system by sign test], 
#     where each inner arrayref has one element per n-gram order considered
sub statisticallyCompareSystemResults
{
	my ($self, $sysname1, $sysname2, $factorName) = @_;
	#check in-memory cache first
	if(exists $self->{'comparisonStats'}->{$sysname1} && exists $self->{'comparisonStats'}->{$sysname1}->{$sysname2} 
		&& exists $self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName})
	{
		return $self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName};
	}
	warn "comparing sysoutputs\n";
	
	$self->ensureFilenameDefined($sysname1);
	$self->ensureFilenameDefined($sysname2);
	$self->ensureFactorPosDefined($factorName);
	#make sure we have tallied results for both systems
	if(!exists $self->{'subsetBLEUstats'}->{$sysname1}->{$factorName}) {$self->statisticallyTestBLEUResults($sysname1, $factorName);}
	if(!exists $self->{'subsetBLEUstats'}->{$sysname2}->{$factorName}) {$self->statisticallyTestBLEUResults($sysname2, $factorName);}
	
	if(!exists $self->{'comparisonStats'}->{$sysname1}) {$self->{'comparisonStats'}->{$sysname1} = {};}
	if(!exists $self->{'comparisonStats'}->{$sysname1}->{$sysname2}) {$self->{'comparisonStats'}->{$sysname1}->{$sysname2} = {};}
	if(!exists $self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName}) {$self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName} = [];}
	my ($tConfidences, $tWinningIndices, $signConfidences, $signWinningIndices) = ([], [], [], []);
	for(my $i = 0; $i < 4; $i++) #loop over n-gram order
	{
		#t-test stats
		my ($mean, $dev) = (0, 0); #of the difference between the first and second systems' precisions
		#sign-test stats
		my ($nPlus, $nMinus) = (0, 0);
		my $j;
		for($j = 0; $j < scalar(@{$self->{'subsetBLEUstats'}->{$sysname1}->{$factorName}}); $j++)
		{
			my ($stats1, $stats2) = ($self->{'subsetBLEUstats'}->{$sysname1}->{$factorName}->[$j], $self->{'subsetBLEUstats'}->{$sysname2}->{$factorName}->[$j]);
			my ($prec1, $prec2) = ($stats1->[2 * $i] / $stats1->[2 * $i + 1], $stats2->[2 * $i] / $stats2->[2 * $i + 1]); #n-gram precisions
			$mean += $prec1 - $prec2;
			if($prec1 > $prec2) {$nPlus++;} else {$nMinus++;}
		}
		$mean /= $j;
		for($j = 0; $j < scalar(@{$self->{'subsetBLEUstats'}->{$sysname1}->{$factorName}}); $j++)
		{
			my ($stats1, $stats2) = ($self->{'subsetBLEUstats'}->{$sysname1}->{$factorName}->[$j], $self->{'subsetBLEUstats'}->{$sysname2}->{$factorName}->[$j]);
			my ($prec1, $prec2) = ($stats1->[2 * $i] / $stats1->[2 * $i + 1], $stats2->[2 * $i] / $stats2->[2 * $i + 1]); #n-gram precisions
			$dev += ($prec1 - $prec2 - $mean) ** 2;
		}
		$dev = sqrt($dev / (($j - 1) * $j)); #need the extra j because the variance of Xbar is 1/n the variance of X
		#t test
		my $t = $mean / $dev; #this isn't the standard form; remember the difference of the means is equal to the mean of the differences
		my $cc = getUpperBoundPValue($t);
		print STDERR "comparing at n=$i: mu $mean, sigma $dev, t $t -> conf >= " . (1 - $cc) . "\n";
		push @$tConfidences, $cc;
		push @$tWinningIndices, ($mean > 0) ? 0 : 1;
		#sign test
		my %binomialCoefficients; #map (n+ - n-) to a coefficient; compute on the fly!
		for(my $k = 0; $k <= $nPlus + $nMinus; $k++)
		{
			$binomialCoefficients{$k} = binCoeff($nPlus + $nMinus, $k);
		}
		my $sumCoeffs = 0;
		foreach my $coeff (values %binomialCoefficients) #get a lower bound on the probability mass inside (n+ - n-)
		{
			if($coeff > $binomialCoefficients{$nPlus}) {$sumCoeffs += $coeff;}
		}
		push @$signConfidences, $sumCoeffs;
		push @$signWinningIndices, ($nPlus > $nMinus) ? 0 : 1;
	}
	$self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName} = [$tConfidences, $tWinningIndices, $signConfidences, $signWinningIndices];
	return $self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName};
}

#write HTML to be displayed to compare the various versions we have of each sentence in the corpus;
#allow to filter which versions will be displayed
#(we don't write the whole page, just the contents of the body)
#arguments: filehandleref to which to write, regex to filter filename extensions to be included
#return: none
sub writeComparisonPage
{
	my ($self, $fh, $filter) = @_;
	my @filteredExtensions = grep($filter, ('e', 'f', keys %{$self->{'sysoutFilenames'}}));
	my %openedFiles = $self->openFiles(@filteredExtensions);
	my $id = 1; #sentence ID string
	while(my %lines = $self->readLineFromFiles(%openedFiles))
	{
		$self->printSingleSentenceComparison($fh, $id, %lines);
		$id++;
	}
	$self->closeFiles(%openedFiles);
}

##########################################################################################################
#####     INTERNAL     ###################################################################################
##########################################################################################################

#destructor!
#arguments: none
#return: none
sub DESTROY
{
	my $self = shift;
	$self->writeCacheFile();
}

#write all scores in memory to disk
#arguments: none
#return: none
sub writeCacheFile
{
	my $self = shift;
	if(!open(CACHEFILE, ">" . $self->{'cacheFilename'}))
	{
		warn "Corpus::writeCacheFile(): can't open '" . $self->{'cacheFilename'} . "' for write\n";
		return;
	}

	#store file changetimes to disk
	print CACHEFILE "File changetimes\n";
	my $ensureCtimeIsOutput = sub
	{
		my $ext = shift;
		#check for a previously read value
		if(exists $self->{'fileCtimes'}->{$ext} && $self->cacheIsCurrentForFile($ext)) {print CACHEFILE "$ext " . $self->{'fileCtimes'}->{$ext} . "\n";}
		else {print CACHEFILE "$ext " . time . "\n";} #our info must just have been calculated
	};
	if(exists $self->{'truthFilename'}) {&$ensureCtimeIsOutput('e');}
	if(exists $self->{'inputFilename'}) {&$ensureCtimeIsOutput('f');}
	foreach my $factorName (keys %{$self->{'phraseTableFilenames'}}) {&$ensureCtimeIsOutput("pt_$factorName");}
	foreach my $sysname (keys %{$self->{'sysoutFilenames'}}) {&$ensureCtimeIsOutput($sysname);}
	#store bleu scores to disk
	print CACHEFILE "\nBLEU scores\n";
	foreach my $sysname (keys %{$self->{'bleuScores'}})
	{
		foreach my $factorName (keys %{$self->{'bleuScores'}->{$sysname}})
		{
			print CACHEFILE "$sysname $factorName " . join(' ', @{$self->{'bleuScores'}->{$sysname}->{$factorName}->[0]});
			foreach my $sentenceBLEU (@{$self->{'bleuScores'}->{$sysname}->{$factorName}->[1]})
			{
				print CACHEFILE ";" . join(' ', @$sentenceBLEU);
			}
			print CACHEFILE "\n";
		}
	}
	#store t statistics for overall BLEU score and subsets in k-fold cross-validation
	print CACHEFILE "\nBLEU statistics\n";
	foreach my $sysname (keys %{$self->{'bleuConfidence'}})
	{
		foreach my $factorName (keys %{$self->{'bleuConfidence'}->{$sysname}})
		{
			print CACHEFILE "$sysname $factorName " . join(' ', @{$self->{'bleuConfidence'}->{$sysname}->{$factorName}->[0]});
			foreach my $subsetConfidence (@{$self->{'bleuConfidence'}->{$sysname}->{$factorName}->[1]})
			{
				print CACHEFILE ";" . join(' ', @$subsetConfidence);
			}
			print CACHEFILE "\n";
		}
	}
	#store statistics comparing system outputs
	print CACHEFILE "\nStatistical comparisons\n";
	foreach my $sysname1 (keys %{$self->{'comparisonStats'}})
	{
		foreach my $sysname2 (keys %{$self->{'comparisonStats'}->{$sysname1}})
		{
			foreach my $factorName (keys %{$self->{'comparisonStats'}->{$sysname1}->{$sysname2}})
			{
				print CACHEFILE "$sysname1 $sysname2 $factorName " . join(';', map {join(' ', @$_)} @{$self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName}}) . "\n";
			}
		}
	}
	#store unknown-token counts to disk
	print CACHEFILE "\nUnknown-token counts\n";
	foreach my $factorName (keys %{$self->{'unknownCount'}})
	{
		print CACHEFILE $factorName . " " . $self->{'phraseTableFilenames'}->{$factorName} . " " . $self->{'unknownCount'}->{$factorName} . " " . $self->{'tokenCount'}->{'input'} . "\n";
	}
	#store WER, PWER to disk
	print CACHEFILE "\nWER scores\n";
	my $printWERFunc = 
	sub
	{
		my $werType = shift;
		foreach my $sysname (keys %{$self->{$werType}})
		{
			foreach my $factorName (keys %{$self->{$werType}->{$sysname}})
			{
				my ($totalWER, $sentenceWERs, $errorWords) = @{$self->{$werType}->{$sysname}->{$factorName}};
				print CACHEFILE "$werType $sysname $factorName $totalWER " . join(' ', @$sentenceWERs);
				foreach my $indices (@$errorWords)
				{
					print CACHEFILE ";" . join(' ', @$indices);
				}
				print CACHEFILE "\n";
			}
		}
	};
	&$printWERFunc('sysoutWER');
	&$printWERFunc('sysoutPWER');
	#store corpus perplexities to disk
	print CACHEFILE "\nPerplexity\n";
	foreach my $sysname (keys %{$self->{'perplexity'}})
	{
		foreach my $factorName (keys %{$self->{'perplexity'}->{$sysname}})
		{
			print CACHEFILE "$sysname $factorName " . $self->{'perplexity'}->{$sysname}->{$factorName} . "\n";
		}
	}
	print "\nNN/ADJ WER/PWER\n";
	foreach my $sysname (keys %{$self->{'nnAdjWERPWER'}})
	{
		print CACHEFILE "$sysname " . join(' ', @{$self->{'nnAdjWERPWER'}->{$sysname}}) . "\n";
	}
	print "\n";
	close(CACHEFILE);
}

#load all scores present in the cache file into the appropriate fields of $self
#arguments: none
#return: none
sub loadCacheFile
{
	my $self = shift;
	if(!open(CACHEFILE, "<" . $self->{'cacheFilename'}))
	{
		warn "Corpus::loadCacheFile(): can't open '" . $self->{'cacheFilename'} . "' for read\n";
		return;
	}
	my $mode = 'none';
	while(my $line = <CACHEFILE>)
	{
		next if $line =~ /^[ \t\n\r\x0a]*$/; #anyone know why char 10 (0x0a) shows up on empty lines, at least on solaris?
		chomp $line;
		#check for start of section
		if($line =~ /File changetimes/) {$mode = 'ctime';}
		elsif($line =~ /BLEU scores/) {$mode = 'bleu';}
		elsif($line =~ /BLEU statistics/) {$mode = 'bstats';}
		elsif($line =~ /Statistical comparisons/) {$mode = 'cmp';}
		elsif($line =~ /Unknown-token counts/) {$mode = 'unk';}
		elsif($line =~ /WER scores/) {$mode = 'wer';}
		elsif($line =~ /Perplexity/) {$mode = 'ppl';}
		elsif($line =~ /NN\/ADJ WER\/PWER/) {$mode = 'nawp';}
		#get data when in a mode already
		elsif($mode eq 'ctime')
		{
			local ($fileExtension, $ctime) = split(/\s+/, $line);
			$self->{'fileCtimes'}->{$fileExtension} = $ctime;
		}
		elsif($mode eq 'bleu')
		{
			local ($sysname, $factorName, $rest) = split(/\s+/, $line, 3);
			next if !$self->cacheIsCurrentForFile($sysname) || !$self->cacheIsCurrentForFile('e');
			if(!exists $self->{'bleuScores'}->{$sysname}) {$self->{'bleuScores'}->{$sysname} = {};}
			if(!exists $self->{'bleuScores'}->{$sysname}->{$factorName}) {$self->{'bleuScores'}->{$sysname}->{$factorName} = [[], []];}
			my @stats = map {my @tmp = split(/\s+/, $_); \@tmp;} split(/;/, $rest);
			print STDERR "bleu 1: " . join(', ', @{shift @stats}) . "\n";
			print STDERR "bleu 2: " . join(' ', map {"{" . join(', ', @$_) . "}"} @stats) . "\n";
		#	$self->{'bleuScores'}->{$sysname}->{$factorName}->[0] = shift @stats;
		#	$self->{'bleuScores'}->{$sysname}->{$factorName}->[1] = \@stats;
		}
		elsif($mode eq 'bstats')
		{
			local ($sysname, $factorName, $rest) = split(/\s+/, $line, 3);
			next if !$self->cacheIsCurrentForFile($sysname) || !$self->cacheIsCurrentForFile('e');
			if(!exists $self->{'bleuConfidence'}->{$sysname}) {$self->{'bleuConfidence'}->{$sysname} = {};}
			if(!exists $self->{'bleuConfidence'}->{$sysname}->{$factorName}) {$self->{'bleuConfidence'}->{$sysname}->{$factorName} = [[], []];}
			my @stats = map {my @tmp = split(/\s+/, $_); \@tmp;} split(/;/, $rest);
			$self->{'bleuConfidence'}->{$sysname}->{$factorName}->[0] = shift @stats;
			$self->{'bleuConfidence'}->{$sysname}->{$factorName}->[1] = \@stats;
		}
		elsif($mode eq 'cmp')
		{
			local ($sysname1, $sysname2, $factorName, $rest) = split(/\s+/, $line, 4);
			next if !$self->cacheIsCurrentForFile($sysname1) || !$self->cacheIsCurrentForFile($sysname2) || !$self->cacheIsCurrentForFile('e');
			if(!exists $self->{'comparisonStats'}->{$sysname1}) {$self->{'comparisonStats'}->{$sysname1} = {};}
			if(!exists $self->{'comparisonStats'}->{$sysname1}->{$sysname2}) {$self->{'comparisonStats'}->{$sysname1}->{$sysname2} = {};}
			if(!exists $self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName}) {$self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName} = [];}
			my @stats = map {my @x = split(' ', $_); \@x} split(/;/, $rest);
			$self->{'comparisonStats'}->{$sysname1}->{$sysname2}->{$factorName} = \@stats;