format_lm.sh
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#!/usr/bin/env bash
# Copyright 2012 Arnab Ghoshal
# 2010-2011 Microsoft Corporation
# 2016-2018 Johns Hopkins University (author: Daniel Povey)
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
# WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
# MERCHANTABLITY OR NON-INFRINGEMENT.
# See the Apache 2 License for the specific language governing permissions and
# limitations under the License.
set -e
if [ $# -ne 4 ]; then
echo "Usage: $0 <lang_dir> <arpa-LM> <lexicon> <out_dir>"
echo "E.g.: $0 data/lang data/local/lm/foo.kn.gz data/local/dict/lexicon.txt data/lang_test"
echo "Convert ARPA-format language models to FSTs.";
exit 1;
fi
lang_dir=$1
lm=$2
lexicon=$3
out_dir=$4
mkdir -p $out_dir
[ -f ./path.sh ] && . ./path.sh
echo "Converting '$lm' to FST"
# the -ef test checks if source and target directory
# are two different directories in the filesystem
# if they are the same, the section guarded by the test
# would be actually harmfull (deleting the phones/ subdirectory)
if [ -e $out_dir ] && [ ! $lang_dir -ef $out_dir ] ; then
if [ -e $out_dir/phones ] ; then
rm -r $out_dir/phones
fi
for f in phones.txt words.txt topo L.fst L_disambig.fst phones oov.int oov.txt; do
cp -r $lang_dir/$f $out_dir
done
fi
lm_base=$(basename $lm '.gz')
gunzip -c $lm \
| arpa2fst --disambig-symbol=#0 \
--read-symbol-table=$out_dir/words.txt - $out_dir/G.fst
set +e
fstisstochastic $out_dir/G.fst
set -e
# The output is like:
# 9.14233e-05 -0.259833
# we do expect the first of these 2 numbers to be close to zero (the second is
# nonzero because the backoff weights make the states sum to >1).
# Everything below is only for diagnostic.
# Checking that G has no cycles with empty words on them (e.g. <s>, </s>);
# this might cause determinization failure of CLG.
# #0 is treated as an empty word.
mkdir -p $out_dir/tmpdir.g
awk '{if(NF==1){ printf("0 0 %s %s\n", $1,$1); }}
END{print "0 0 #0 #0"; print "0";}' \
< "$lexicon" > $out_dir/tmpdir.g/select_empty.fst.txt
fstcompile --isymbols=$out_dir/words.txt --osymbols=$out_dir/words.txt \
$out_dir/tmpdir.g/select_empty.fst.txt \
| fstarcsort --sort_type=olabel \
| fstcompose - $out_dir/G.fst > $out_dir/tmpdir.g/empty_words.fst
fstinfo $out_dir/tmpdir.g/empty_words.fst | grep cyclic | grep -w 'y' \
&& echo "Language model has cycles with empty words" && exit 1
rm -r $out_dir/tmpdir.g
echo "Succeeded in formatting LM: '$lm'"