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#!/usr/bin/perl -w
use strict;
use utf8;
##### EDIT THESE SETTINGS ####################################################
my $MAX_LENGTH = 99; # discard a sentence if it is longer than this
my $AUTOMATIC_INCLUDE_IF_SHORTER_THAN = 6; # if both are shorter, include
my $MAX_ZSCORE = 1.8; # how far from the mean can the (log)ratio be?
##############################################################################
die "Usage: $0 corpus.fr-en\n\n Filter sentence pairs containing sentences longer than $MAX_LENGTH words\n or whose log length ratios are $MAX_ZSCORE stddevs away from the mean log ratio.\n\n" unless scalar @ARGV == 1;
binmode(STDOUT,":utf8");
binmode(STDERR,":utf8");
my $corpus = shift @ARGV;
die "Cannot read from STDIN\n" if $corpus eq '-';
my $ff = "<$corpus";
$ff = "gunzip -c $corpus|" if $ff =~ /\.gz$/;
open F,$ff or die "Can't read $corpus: $!";
binmode(F,":utf8");
my $rat_max = log(9);
my $lrm = 0;
my $zerof = 0;
my $zeroe = 0;
my $absbadrat = 0;
my $overlene = 0;
my $overlenf = 0;
my $lines = 0;
my @lograts = ();
while(<F>) {
$lines++;
if ($lines % 100000 == 0) { print STDERR " [$lines]\n"; }
elsif ($lines % 2500 == 0) { print STDERR "."; }
my ($sf, $se, @d) = split / \|\|\| /;
die "Bad format: $_" if scalar @d != 0 or !defined $se;
my @fs = split /\s+/, $sf;
my @es = split /\s+/, $se;
my $flen = scalar @fs;
my $elen = scalar @es;
if ($flen == 0) {
$zerof++;
next;
}
if ($elen == 0) {
$zeroe++;
next;
}
if ($flen > $MAX_LENGTH) {
$overlenf++;
next;
}
if ($elen > $MAX_LENGTH) {
$overlene++;
next;
}
if ($elen >= $AUTOMATIC_INCLUDE_IF_SHORTER_THAN ||
$flen >= $AUTOMATIC_INCLUDE_IF_SHORTER_THAN) {
my $lograt = log($flen) - log($elen);
if (abs($lograt) > $rat_max) {
$absbadrat++;
next;
}
$lrm += $lograt;
push @lograts, $lograt;
}
}
close F;
print STDERR "\nComputing statistics...\n";
my $lmean = $lrm / scalar @lograts;
my $lsd = 0;
for my $lr (@lograts) {
$lsd += ($lr - $lmean)**2;
}
$lsd = sqrt($lsd / scalar @lograts);
@lograts = ();
my $pass1_discard = $zerof + $zeroe + $absbadrat + $overlene + $overlenf;
my $discard_rate = int(10000 * $pass1_discard / $lines) / 100;
print STDERR " Total lines: $lines\n";
print STDERR " Already discared: $pass1_discard\t(discard rate = $discard_rate%)\n";
print STDERR " Mean F:E ratio: " . exp($lmean) . "\n";
print STDERR " StdDev F:E ratio: " . exp($lsd) . "\n";
print STDERR "Writing...\n";
open F,$ff or die "Can't reread $corpus: $!";
binmode(F,":utf8");
my $to = 0;
my $zviol = 0;
my $worstz = -1;
my $worst = "\n";
$lines = 0;
while(<F>) {
$lines++;
if ($lines % 100000 == 0) { print STDERR " [$lines]\n"; }
elsif ($lines % 2500 == 0) { print STDERR "."; }
my ($sf, $se) = split / \|\|\| /;
my @fs = split /\s+/, $sf;
my @es = split /\s+/, $se;
my $flen = scalar @fs;
my $elen = scalar @es;
next if ($flen == 0);
next if ($elen == 0);
next if ($flen > $MAX_LENGTH);
next if ($elen > $MAX_LENGTH);
if ($elen >= $AUTOMATIC_INCLUDE_IF_SHORTER_THAN ||
$flen >= $AUTOMATIC_INCLUDE_IF_SHORTER_THAN) {
my $lograt = log($flen) - log($elen);
if (abs($lograt) > $rat_max) {
$absbadrat++;
next;
}
my $zscore = abs($lograt - $lmean) / $lsd;
if ($elen > $AUTOMATIC_INCLUDE_IF_SHORTER_THAN &&
$flen > $AUTOMATIC_INCLUDE_IF_SHORTER_THAN && $zscore > $worstz) { $worstz = $zscore; $worst = $_; }
if ($zscore > $MAX_ZSCORE) {
$zviol++;
next;
}
print;
}
$to++;
}
my $discard_rate2 = int(10000 * $zviol / ($lines - $pass1_discard)) / 100;
print STDERR "\n Lines printed: $to\n Ratio violations: $zviol\t(discard rate = $discard_rate2%)\n";
print STDERR " Worst z-score: $worstz\n sentence: $worst";
exit 0;
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