[scripts] add script to compute dev PPL on kaldi-rnnlm (#3340)

scripts/rnnlm/compute_perplexity.sh

@@ -0,0 +1,48 @@
+#!/bin/bash
+
+# This script computes perplexity of text on the specified RNNLM model. 
+
+[ -f ./path.sh ] && . ./path.sh
+. utils/parse_options.sh
+
+if [ $# != 2 ]; then
+  echo "Usage: $0 <rnn-dir> <input-text>"
+  exit 1
+fi
+
+dir=$1
+text_in=$2
+
+# the format of the $text_in file is one sentence per line, without explicit
+# <s> or </s> symbols, and without utterance-id's, for example:
+
+# ====== begin file ======
+# well western new york is supposed to be used to this kind of weather but
+# yeah you are right
+# in um anaheim california you know just
+# ====== end file ======
+
+if [ -f $dir/word_embedding.final.mat ]; then
+  word_embedding=$dir/word_embedding.final.mat
+else
+  [ ! -f $dir/feat_embedding.final.mat ] &&
+             echo "$0: expect file $dir/feat_embedding.final.mat to exit"
+  word_embedding="rnnlm-get-word-embedding $dir/word_feats.txt $dir/feat_embedding.final.mat -|"
+fi
+
+for x in final.raw config/words.txt; do
+  if [ ! -f $dir/$x ]; then 
+    echo "$0: expected file $dir/$x to exist."
+    exit 1;
+  fi
+done
+
+special_symbol_opts=$(cat $dir/special_symbol_opts.txt)
+
+ppl=$(rnnlm-sentence-probs --normalize-probs=true \
+       $special_symbol_opts $dir/final.raw "$word_embedding" \
+       <(cat $text_in | sym2int.pl $dir/config/words.txt | awk '{print "utt_id ", $0}') | \
+       awk '{for(i=2;i<=NF;i++) a+=$i; b+=NF-1}END{print exp(-a / b)}')
+
+echo "$0: perplexity is $ppl"
+