Initial commit

verl/utils/tokenizer.py

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+# Copyright 2024 Bytedance Ltd. and/or its affiliates
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Utils for tokenization."""
+import warnings
+
+__all__ = ['hf_tokenizer']
+
+
+def set_pad_token_id(tokenizer):
+    """Set pad_token_id to eos_token_id if it is None.
+
+    Args:
+        tokenizer (transformers.PreTrainedTokenizer): The tokenizer to be set.
+
+    """
+    if tokenizer.pad_token_id is None:
+        tokenizer.pad_token_id = tokenizer.eos_token_id
+        warnings.warn(f'tokenizer.pad_token_id is None. Now set to {tokenizer.eos_token_id}')
+    if tokenizer.pad_token is None:
+        tokenizer.pad_token = tokenizer.eos_token
+        warnings.warn(f'tokenizer.pad_token is None. Now set to {tokenizer.eos_token}')
+
+
+def hf_tokenizer(name_or_path, correct_pad_token=True, correct_gemma2=True, **kwargs):
+    """Create a huggingface pretrained tokenizer.
+
+    Args:
+        name (str): The name of the tokenizer.
+        correct_pad_token (bool): Whether to correct the pad token id.
+        correct_gemma2 (bool): Whether to correct the gemma2 tokenizer.
+        **kwargs: The keyword arguments for the tokenizer.
+
+    Returns:
+        transformers.PreTrainedTokenizer: The pretrained tokenizer.
+
+    """
+    from transformers import AutoTokenizer
+    if correct_gemma2 and isinstance(name_or_path, str) and 'gemma-2-2b-it' in name_or_path:
+        # the EOS token in gemma2 is ambiguious, which may worsen RL performance.
+        # https://huggingface.co/google/gemma-2-2b-it/commit/17a01657f5c87135bcdd0ec7abb4b2dece04408a
+        warnings.warn('Found gemma-2-2b-it tokenizer. Set eos_token and eos_token_id to <end_of_turn> and 107.')
+        kwargs['eos_token'] = '<end_of_turn>'
+        kwargs['eos_token_id'] = 107
+    tokenizer = AutoTokenizer.from_pretrained(name_or_path, **kwargs)
+    if correct_pad_token:
+        set_pad_token_id(tokenizer)
+    return tokenizer