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| """Byte pair encoding utilities""" | |
| import os | |
| import json | |
| import regex as re | |
| from functools import lru_cache | |
| def bytes_to_unicode(): | |
| """ | |
| Returns list of utf-8 byte and a corresponding list of unicode strings. | |
| The reversible bpe codes work on unicode strings. | |
| This means you need a large # of unicode characters in your vocab if you want to avoid UNKs. | |
| When you're at something like a 10B token dataset you end up needing around 5K for decent coverage. | |
| This is a signficant percentage of your normal, say, 32K bpe vocab. | |
| To avoid that, we want lookup tables between utf-8 bytes and unicode strings. | |
| And avoids mapping to whitespace/control characters the bpe code barfs on. | |
| """ | |
| bs = list(range(ord("!"), ord("~")+1))+list(range(ord("¡"), ord("¬")+1))+list(range(ord("®"), ord("ÿ")+1)) | |
| cs = bs[:] | |
| n = 0 | |
| for b in range(2**8): | |
| if b not in bs: | |
| bs.append(b) | |
| cs.append(2**8+n) | |
| n += 1 | |
| cs = [chr(n) for n in cs] | |
| return dict(zip(bs, cs)) | |
| def get_pairs(word): | |
| """Return set of symbol pairs in a word. | |
| Word is represented as tuple of symbols (symbols being variable-length strings). | |
| """ | |
| pairs = set() | |
| prev_char = word[0] | |
| for char in word[1:]: | |
| pairs.add((prev_char, char)) | |
| prev_char = char | |
| return pairs | |
| class Encoder: | |
| def __init__(self, encoder, bpe_merges, errors='replace'): | |
| self.encoder = encoder | |
| self.decoder = {v:k for k,v in self.encoder.items()} | |
| self.errors = errors # how to handle errors in decoding | |
| self.byte_encoder = bytes_to_unicode() | |
| self.byte_decoder = {v:k for k, v in self.byte_encoder.items()} | |
| self.bpe_ranks = dict(zip(bpe_merges, range(len(bpe_merges)))) | |
| self.cache = {} | |
| # Should haved added re.IGNORECASE so BPE merges can happen for capitalized versions of contractions | |
| self.pat = re.compile(r"""'s|'t|'re|'ve|'m|'ll|'d| ?\p{L}+| ?\p{N}+| ?[^\s\p{L}\p{N}]+|\s+(?!\S)|\s+""") | |
| def bpe(self, token): | |
| if token in self.cache: | |
| return self.cache[token] | |
| word = tuple(token) | |
| pairs = get_pairs(word) | |
| if not pairs: | |
| return token | |
| while True: | |
| bigram = min(pairs, key = lambda pair: self.bpe_ranks.get(pair, float('inf'))) | |
| if bigram not in self.bpe_ranks: | |
| break | |
| first, second = bigram | |
| new_word = [] | |
| i = 0 | |
| while i < len(word): | |
| try: | |
| j = word.index(first, i) | |
| new_word.extend(word[i:j]) | |
| i = j | |
| except: | |
| new_word.extend(word[i:]) | |
| break | |
| if word[i] == first and i < len(word)-1 and word[i+1] == second: | |
| new_word.append(first+second) | |
| i += 2 | |
| else: | |
| new_word.append(word[i]) | |
| i += 1 | |
| new_word = tuple(new_word) | |
| word = new_word | |
| if len(word) == 1: | |
| break | |
| else: | |
| pairs = get_pairs(word) | |
| word = ' '.join(word) | |
| self.cache[token] = word | |
| return word | |
| def encode(self, text): | |
| bpe_tokens = [] | |
| for token in re.findall(self.pat, text): | |
| token = ''.join(self.byte_encoder[b] for b in token.encode('utf-8')) | |
| bpe_tokens.extend(self.encoder[bpe_token] for bpe_token in self.bpe(token).split(' ')) | |
| return bpe_tokens | |
| def decode(self, tokens): | |
| text = ''.join([self.decoder[token] for token in tokens]) | |
| text = bytearray([self.byte_decoder[c] for c in text]).decode('utf-8', errors=self.errors) | |
| return text | |
| def get_encoder(model_name, models_dir): | |
| with open(os.path.join(models_dir, model_name, 'encoder.json'), 'r') as f: | |
| encoder = json.load(f) | |
| with open(os.path.join(models_dir, model_name, 'vocab.bpe'), 'r', encoding="utf-8") as f: | |
| bpe_data = f.read() | |
| bpe_merges = [tuple(merge_str.split()) for merge_str in bpe_data.split('\n')[1:-1]] | |
| return Encoder( | |
| encoder=encoder, | |
| bpe_merges=bpe_merges, | |
| ) | |
| def get_encoder_from_strings(vocab, bpe_data): | |
| encoder = json.loads(vocab) | |
| bpe_merges = [tuple(merge_str.split()) for merge_str in bpe_data.split('\n')[1:-1]] | |
| return Encoder( | |
| encoder=encoder, | |
| bpe_merges=bpe_merges, | |
| ) | |