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Improve HF tokenization hack to cover multiple special tokens #649

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Improve HF tokenization hack to cover multiple special tokens #649

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c4fc9d5
Improve HF tokenization hack to cover multiple tokens
shawnz Feb 21, 2024
1f74135
Oops, include last token in loop
shawnz Feb 21, 2024
e17bb18
Get list of special tokens from tokenizer
shawnz Feb 22, 2024
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25 changes: 20 additions & 5 deletions guidance/models/_model.py
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Original file line number Diff line number Diff line change
Expand Up @@ -613,13 +613,28 @@ def _cleanup_tokens(self, token_ids, token_byte_positions):
for i,id in enumerate(joint_token_ids):
pos += len(self.tokenizer.tokens[id])
token_byte_positions.append(pos)

# ugly hack to deal with sentence peice craziness of space hiding after special tokens TODO: figure out how to make this more robust
if token_byte_positions[-1] == last_pos + 1 and self.tokenizer.tokens[token_ids[0]] == b'<s>' and self.tokenizer.tokens[token_ids[1]][0:1] == b' ':
for i in range(1, len(token_byte_positions)):
token_byte_positions[i] -= 1
if (
hasattr(self.tokenizer, "_orig_tokenizer")
and hasattr(self.tokenizer._orig_tokenizer, "all_special_tokens")
and token_byte_positions[-1] > last_pos
):
special_tokens = [
bytes(s, encoding="utf8")
for s in self.tokenizer._orig_tokenizer.all_special_tokens
]
spaces_hidden = 0
for i in range(0, len(token_byte_positions)):
token_byte_positions[i] -= spaces_hidden
if (
self.tokenizer.tokens[token_ids[i]] in special_tokens
and len(token_ids) > i + 1
and self.tokenizer.tokens[token_ids[i + 1]][0:1] == b" "
):
spaces_hidden += 1
assert token_byte_positions[-1] == last_pos

return token_ids, token_byte_positions

def get_logits(self, token_ids, forced_bytes, current_temp):
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11 changes: 6 additions & 5 deletions guidance/models/transformers/_transformers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -95,13 +95,14 @@ def _model_and_tokenizer(self, model, tokenizer, **kwargs):
def _joint_tokenize(self, token_ids):
# first_decode = self.tokenizer._orig_tokenizer.decode(token_ids)
first_decode = b''.join([self.tokenizer.tokens[id] for id in token_ids]).decode("utf8")

# HACK: work around a bug in the HuggingFace tokenizer (that will just add extra spaces during an encode-decode cycle)
if hasattr(self.tokenizer._orig_tokenizer, "all_special_tokens"):
for special_token in self.tokenizer._orig_tokenizer.all_special_tokens:
first_decode = first_decode.replace(f"{special_token} ", special_token)

new_ids = self.tokenizer._orig_tokenizer(first_decode, add_special_tokens=False)["input_ids"]

# HACK: check for a bug in the HuggingFace tokenizer (that will just add extra spaces during an encode-decode cycle)
second_decode = self.tokenizer._orig_tokenizer.decode(new_ids)
if second_decode != first_decode and len(second_decode) == len(first_decode) + 1 and second_decode.startswith("<s> "):
new_ids = new_ids[0:1] + new_ids[2:]

return new_ids

def get_logits(self, token_ids, forced_bytes, current_temp):
Expand Down
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