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shingles.py
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shingles.py
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# -*- coding: UTF-8 -*-
from optparse import OptionParser
import random
import itertools
MAXGENPRIMEINDEX = 20
MINGENPRIMTINDEX = 5
HASH_COUNT = 84
SUPERGROUPS = 6
SUPER_SIZE = HASH_COUNT / SUPERGROUPS
def gen_prime(index):
D = {}
q = 2
gen_index = 0
while True:
if q not in D:
gen_index += 1
if gen_index == index:
return q
D[q * q] = [q]
else:
for p in D[q]:
D.setdefault(p + q, []).append(p)
del D[q]
q += 1
def readfile(filename):
with open(filename) as f:
return f.read().replace('\n', ' ')
def canonize(source):
stop_symbols = '.,!?:;-\n\r()'
stop_words = (u'это', u'как', u'так', u'и', u'в', u'над', u'к', u'до', u'не', u'на', u'но', u'за', u'то', u'с',
u'ли', u'а', u'во', u'от', u'со', u'для', u'о', u'же', u'ну', u'вы', u'бы', u'что', u'кто', u'он', u'она')
return ([x for x in [y.strip(stop_symbols).decode('UTF-8') for y in source.lower().split()] if x and (x not in stop_words)])
def gen_hash():
prime = gen_prime(random.randint(MINGENPRIMTINDEX, MAXGENPRIMEINDEX))
base = random.randint(prime, 2*prime)
return (base, prime)
def prepare_hashes(count):
return [gen_hash() for i in xrange(count)]
def calc_hash(shingle, func):
s = ''.join(shingle)
base, prime = func
value = 0
for i in xrange(len(s)):
value += ord(s[i])*pow(base, i) % prime
return value
def calc_shingles(text, size, hashes):
matrix = []
for i in xrange(len(text) - (size - 1)):
shignle = [x for x in text[i:i + size]]
matrix.append([calc_hash(shignle, func) for func in hashes])
transposed = map(list, zip(*matrix))
return [min(transposed[i]) for i in xrange(HASH_COUNT)]
def compare_shingles(shingles1, shingles2):
same = 0.0
for h1, h2 in zip(shingles1, shingles2):
if h1 == h2:
same += 1.0
return same / HASH_COUNT
def gen_super_map():
m = [None]*HASH_COUNT
used = [False]*HASH_COUNT
for i in xrange(SUPERGROUPS):
for j in xrange(SUPER_SIZE):
k = random.randint(0, HASH_COUNT - 1)
while used[k]:
k = random.randint(0, HASH_COUNT - 1)
used[k] = True
m[k] = (i, j)
return m
def calc_super(shingles, mapping):
ret = [[None]*SUPER_SIZE]*SUPERGROUPS
for i in xrange(HASH_COUNT):
num, idx = mapping[i]
ret[num][idx] = shingles[i]
return ret
def compare_super(sup1, sup2):
sum = 0.0
for i in xrange(SUPERGROUPS):
eq = True
for j in xrange(SUPER_SIZE):
if sup1[i][j] != sup2[i][j]:
eq = False
if eq:
sum += 1.0
return sum / SUPERGROUPS
def calc_mega(supers, combinations):
megas = []
for i, j in combinations:
m = list(supers[i])
m.extend(supers[j])
megas.append(m)
return megas
def compare_mega(megas1, megas2):
same = 0.0
for m1, m2 in zip(megas1, megas2):
eq = True
for e1, e2 in zip(m1, m2):
if e1 != e2:
eq = False
if eq:
same += 1.0
return same / len(megas1)
def main():
parser = OptionParser()
parser.add_option("-a", "--file1")
parser.add_option("-b", "--file2")
parser.add_option("-s", "--size", type='int', default=10)
(options, args) = parser.parse_args()
text1 = canonize(readfile(options.file1))
text2 = canonize(readfile(options.file2))
hashes = prepare_hashes(HASH_COUNT)
shingles1 = calc_shingles(text1, options.size, hashes)
shingles2 = calc_shingles(text2, options.size, hashes)
print "shingles compare: ", compare_shingles(shingles1, shingles2)
m = gen_super_map()
sup1 = calc_super(shingles1, m)
sup2 = calc_super(shingles2, m)
print "super compare: ", compare_super(sup1, sup2)
comb = list(itertools.combinations(xrange(SUPERGROUPS), 2))
mega1 = calc_mega(sup1, comb)
mega2 = calc_mega(sup2, comb)
print "mega compare: ", compare_mega(mega1, mega2)
if __name__ == '__main__':
main()