Calculating coverage

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Simple bidix-trimmed coverage testing

First install apertium-cleanstream:

svn checkout https://svn.code.sf.net/p/apertium/svn/trunk/apertium-tools/apertium-cleanstream
cd apertium-cleanstream
make
sudo cp apertium-cleanstream /usr/local/bin

Note - After Apertium's migration to GitHub, this tool is read-only on the SourceForge repository and does not exist on GitHub. If you are interested in migrating this tool to GitHub, see Migrating tools to GitHub.

Then save this as coverage.sh:

#!/bin/bash
mode=$1
outfile=/tmp/$mode.clean
apertium -d . $mode | apertium-cleanstream -n > $outfile
total=$(grep -c '^\^' $outfile)
unknown=$(grep -c '/\*' $outfile)
bidix_unknown=$(grep -c '/@' $outfile)
known_percent=$(calc -p  "round( 100*($total-$unknown-$bidix_unknown)/$total, 3)")
echo "$known_percent % known tokens ($unknown unknown, $bidix_unknown bidix-unknown of total $total tokens)"
echo "Top unknown words:"
grep '/[*@]' $outfile | sort | uniq -c | sort -nr | head

And run it like

cat asm.corpus | bash coverage.sh asm-eng-biltrans

(The bidix-unknown count should always be 0 if your pair uses automatic analyser trimming.)

TODO: paradigm-coverage (less naïve)

On an analysed corpus, we can sum frequencies into bins for each lemma+mainpos, so if the analysed corpus contains

musa/mus<n><f><sg><def>/muse<vblex><past>
mus/mus<n><f><sg><ind>/mus<n><f><pl><ind>/muse<vblex><imp>
musene/mus<n><f><pl><def>

then output has

3 mus<n><f>
2 muse<vblex>

and we can find paradigms that are likely to mess up disambiguation, or where we need to ensure that the bidix contains the highest-frequency paradigm (since the bidix is typically smaller than the monodix).

We could also weight these numbers by number of unique forms in the pardef; if the verb pardef has 6 unique forms and then noun only 3, then the above output should be even more skewed:

0.33 mus<n><f>
0.75 muse<vblex>

Faster coverage testing with frequency lists

If words appear several times in your corpus, why bother analysing them several times? We can make a frequency list first and add together the frequencies. This script does some very stupid tokenisation and creates a frequency list:

make-freqlist.sh:

#!/bin/bash

if [[ -t 0 ]]; then
    echo "Expecting a corpus on stdin"
    exit 2
fi

tr '[:space:][:punct:]' '\n' | grep . | sort | uniq -c | sort -nr

And this script runs your analyser, summing up the frequencies:

freqlist-coverage.sh:

#!/bin/bash

set -e -u

if [[ $# -eq 0 || -t 0 ]]; then
    echo "Expecting apertium arguments and a 'sort|uniq -c|sort -nr' style frequency list on stdin"
    echo "For example:"
    echo "\$ < spa.freqlist $0 -d . spa-morph"
    exit 2
fi

sed 's%^ *%<apertium-notrans>%;s% %</apertium-notrans>%;s%$% .%' |
apertium -f html-noent "$@" |
awk -F'</?apertium-notrans>| *\\^\\./\\.<sent><clb>\\$' '
/[/][*@]/ {
    unknown+=$2
    if(!printed) print "Top unknown tokens:"
    if(++printed<10) print $2,$3
    next
}
{
    known+=$2
}
END {
    total=known+unknown
    known_pct=100*known/total
    unk_pct=100*unknown/total
    print known_pct" % known of total "total" tokens"
}'

Usage:

$ chmod +x make-freqlist.sh freqlist-coverage.sh
$ bzcat ~/corpora/nno.txt.bz2 |./make-freqlist.sh > nno.freqlist
$ <nno.freqlist ./freqlist-coverage.sh -d ~/apertium-svn/languages/apertium-nno/ nno-morph

coverage.py

https://svn.code.sf.net/p/apertium/svn/trunk/apertium-tools/coverage.py is a coverage script that wraps curl and bzcat (?)

See also

• Wikipedia dumps
• Cleanstream