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#!/usr/bin/python3
import os
import os.path
import sqlite3
from argparse import ArgumentParser
from operator import itemgetter
from math import log
from sys import float_info
import utils
from myconfig import MyConfig
from dirwalk import walkIndex
config = MyConfig()
#change cwd to the word recognizer directory
words_dir = config.getWordRecognizerDir()
os.chdir(words_dir)
#chdir done
############################################################
# Create Bigram Database #
############################################################
CREATE_BIGRAM_DDL = '''
CREATE TABLE bigram (
prefix TEXT NOT NULL,
postfix TEXT NOT NULL,
freq INTEGER NOT NULL
);
'''
CREATE_BIGRAM_PREFIX_INDEX_DDL = '''
CREATE INDEX bigram_prefix_index on bigram(prefix);
'''
CREATE_BIGRAM_POSTFIX_INDEX_DDL = '''
CREATE INDEX bigram_postfix_index on bigram(postfix);
'''
SELECT_ALL_NGRAM_DML = '''
SELECT words, freq FROM ngram;
'''
INSERT_BIGRAM_DML = '''
INSERT INTO bigram(prefix, postfix, freq) VALUES (?, ?, ?);
'''
def createBigramSqlite(workdir):
print(workdir, 'create bigram')
filename = config.getBigramFileName()
filepath = workdir + os.sep + filename
print(filepath)
if os.access(filepath, os.F_OK):
os.unlink(filepath)
conn = sqlite3.connect(filepath)
cur = conn.cursor()
cur.execute(CREATE_BIGRAM_DDL)
cur.execute(CREATE_BIGRAM_PREFIX_INDEX_DDL)
cur.execute(CREATE_BIGRAM_POSTFIX_INDEX_DDL)
conn.commit()
if conn:
conn.close()
def populateBigramSqlite(workdir):
print(workdir, 'populate bigram')
sep = config.getWordSep()
filename = config.getBigramFileName()
filepath = workdir + os.sep + filename
bigram_conn = sqlite3.connect(filepath)
bigram_cur = bigram_conn.cursor()
length = 2
filename = config.getNgramFileName(length)
filepath = workdir + os.sep + filename
ngram_conn = sqlite3.connect(filepath)
ngram_cur = ngram_conn.cursor()
#begin processing
rows = ngram_cur.execute(SELECT_ALL_NGRAM_DML).fetchall()
for row in rows:
(words_str, freq) = row
words = words_str.strip(sep).split(sep, 1)
assert len(words) == length
(prefix, postfix) = words
bigram_cur.execute(INSERT_BIGRAM_DML, (prefix, postfix, freq))
#print(prefix, postfix, freq)
bigram_conn.commit()
ngram_conn.commit()
if bigram_conn:
bigram_conn.close()
if ngram_conn:
ngram_conn.close()
############################################################
# Information Entropy Model #
############################################################
def computeEntropy(freqs):
#print(freqs)
totalfreq = sum(freqs)
freqs = [ freq / float(totalfreq) for freq in freqs ]
assert abs(1 - sum(freqs)) < len(freqs) * float_info.epsilon
entropy = - sum([ freq * log(freq) for freq in freqs ])
return entropy
############################################################
# Get Threshold Pass #
############################################################
SELECT_PREFIX_DML = '''
SELECT prefix, freq FROM bigram WHERE postfix = ? ;
'''
SELECT_POSTFIX_DML = '''
SELECT postfix, freq FROM bigram WHERE prefix = ? ;
'''
def computePrefixEntropy(cur, word):
rows = cur.execute(SELECT_PREFIX_DML, (word, )).fetchall()
if 0 == len(rows):
return 0.
freqs = []
for row in rows:
(prefix, freq) = row
assert freq >= 1
freqs.append(freq)
return computeEntropy(freqs)
def computePostfixEntropy(cur, word):
rows = cur.execute(SELECT_POSTFIX_DML, (word, )).fetchall()
if 0 == len(rows):
return 0.
freqs = []
for row in rows:
(postfix, freq) = row
assert freq >= 1
freqs.append(freq)
return computeEntropy(freqs)
def computeThreshold(cur, tag):
wordswithentropy = []
wordlistfile = open(config.getWordsListFileName(), "r")
for oneline in wordlistfile.readlines():
oneline = oneline.rstrip(os.linesep)
if len(oneline) == 0:
continue
word = oneline
entropy = 0.
if "prefix" == tag:
entropy = computePrefixEntropy(cur, word)
elif "postfix" == tag:
entropy = computePostfixEntropy(cur, word)
else:
raise "invalid tag value."
#print(word, entropy)
if entropy < config.getMinimumEntropy():
continue
wordswithentropy.append((word, entropy))
wordlistfile.close()
#ascending sort
wordswithentropy.sort(key=itemgetter(1))
pos = int(len(wordswithentropy) * config.getNewWordThreshold())
(word, threshold) = wordswithentropy[-pos]
print(word, threshold)
return threshold
############################################################
# Get Word Pass #
############################################################
|
