simhash+漢明距離計算文本類似度

****因爲最近須要作大規模的文本類似度的計算，因此用到了simhash+漢明距離來快速計算文本的類似度。**
**simhash的原理以下圖:其中的weight採用的是jieba的tf-idf的結果。****

**附上python3的源代碼:**

import math
import jieba
import jieba.analyse

class SimHash(object):

def __init__(self):
    pass
def getBinStr(self, source):
    if source == "":
        return 0
    else:
        x = ord(source[0]) << 7
        m = 1000003
        mask = 2 ** 128 - 1
        for c in source:
            x = ((x * m) ^ ord(c)) & mask
        x ^= len(source)
        if x == -1:
            x = -2
        x = bin(x).replace('0b', '').zfill(64)[-64:]
        return str(x)

def getWeight(self, source):
    # fake weight with keyword
    return ord(source)
def unwrap_weight(self, arr):
    ret = ""
    for item in arr:
        tmp = 0
        if int(item) > 0:
            tmp = 1
        ret += str(tmp)
    return ret

def simHash(self, rawstr):
    seg = jieba.cut(rawstr)
    keywords = jieba.analyse.extract_tags("|".join(seg), topK=100, withWeight=True)
    ret = []
    for keyword, weight in keywords:
        binstr = self.getBinStr(keyword)
        keylist = []
        for c in binstr:
            weight = math.ceil(weight)
            if c == "1":
                keylist.append(int(weight))
            else:
                keylist.append(-int(weight))
        ret.append(keylist)
    # 對列表進行"降維"
    rows = len(ret)
    cols = len(ret[0])
    result = []
    for i in range(cols):
        tmp = 0
        for j in range(rows):
            tmp += int(ret[j][i])
        if tmp > 0:
            tmp = "1"
        elif tmp <= 0:
            tmp = "0"
        result.append(tmp)
    return "".join(result)

def getDistince(self, hashstr1, hashstr2):
    length = 0
    for index, char in enumerate(hashstr1):
        if char == hashstr2[index]:
            continue
        else:
            length += 1
    return length

if name == "__main__":

simhash = SimHash()
s1 = u'I am very happy'
s2 = u'I am very happu'

hash1 = simhash.simHash(s1)
hash2 = simhash.simHash(s2)
distince = simhash.getDistince(hash1, hash2)
value = 5
print("海明距離：", distince, "斷定距離：", value, "是否類似：", distince<=value)