97 строки
2.7 KiB
Python
97 строки
2.7 KiB
Python
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# Copyright (c) Microsoft Corporation. All rights reserved.
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# Licensed under the MIT license.
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import nltk
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def get_pairs(word):
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""" Return set of symbol pairs in a word.
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word is represented as tuple of symbols (symbols being variable-length strings)
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"""
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pairs = set()
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prev_char = word[0]
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for char in word[1:]:
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pairs.add((prev_char, char))
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prev_char = char
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return pairs
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class BPEEncoder(object):
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""" Byte Pair Encoding
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"""
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def __init__(self, bpe_path):
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merges = open(bpe_path, encoding='utf-8').read().split('\n')[1:-1]
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merges = [tuple(merge.split()) for merge in merges]
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self.bpe_ranks = dict(zip(merges, range(len(merges))))
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self.cache = dict()
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def encode(self, sentence):
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tokens = nltk.word_tokenize(sentence)
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bpe_tokens = []
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for token in tokens:
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bpe_tokens.extend(self.bpe(token))
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return bpe_tokens
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def bpe(self, token):
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"""
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Args:
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token (string): a word token
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Returns:
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list: byte pair encodings
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"""
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word = tuple(token[:-1]) + (token[-1] + '</w>',)
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if token in self.cache:
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return self.cache[token]
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pairs = get_pairs(word)
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if not pairs:
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return token+'</w>'
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while True:
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bigram = min(pairs, key = lambda pair: self.bpe_ranks.get(pair, float('inf')))
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if bigram not in self.bpe_ranks:
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break
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first, second = bigram
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new_word = []
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i = 0
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while i < len(word):
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try:
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j = word.index(first, i)
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new_word.extend(word[i:j])
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i = j
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except:
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new_word.extend(word[i:])
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break
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if word[i] == first and i < len(word)-1 and word[i+1] == second:
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new_word.append(first+second)
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i += 2
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else:
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new_word.append(word[i])
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i += 1
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new_word = tuple(new_word)
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word = new_word
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if len(word) == 1:
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break
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else:
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pairs = get_pairs(word)
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word = ' '.join(word)
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if word == '\n </w>':
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word = '\n</w>'
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self.cache[token] = word
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return word.split(' ')
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if __name__ == '__main__':
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sentences = 'trip cost to beijing'
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import nltk
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tokens = nltk.word_tokenize(sentences)
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bpe_encoder = BPEEncoder('../dataset/bpe/vocab_40000.bpe')
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bpe_tokens = []
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for token in tokens:
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print(token)
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bpe_tokens.extend(bpe_encoder.bpe(token))
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print(bpe_tokens)
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