UserWarning: 您正在对解码器专用模型使用 padding_side='right'。这可能会产生不正确的结果。建议设置 `tokenizer.padding_side = 'left'`。
UserWarning: You are using a decoder-only model with padding_side='right'. This may produce incorrect results. Consider setting `tokenizer.padding_side = 'left'`.
ID: huggingface/transformers-tokenizer-padding-side-mismatch
版本兼容性
| 版本 | 状态 | 引入 | 弃用 | 备注 |
|---|---|---|---|---|
| transformers>=4.30.0 | active | — | — | — |
| torch>=1.12.0 | active | — | — | — |
根因分析
解码器专用模型(如 GPT、LLaMA)在批量生成时期望左侧填充;使用右侧填充会导致模型关注序列末尾的填充标记。
English
Decoder-only models (e.g., GPT, LLaMA) expect padding on the left side for batched generation; using right padding causes the model to attend to padding tokens at the end of the sequence.
官方文档
https://huggingface.co/docs/transformers/en/pad_truncation#padding-and-truncation解决方案
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Set padding_side before tokenizing: `tokenizer.padding_side = 'left'` then tokenize the batch again. Example: `tokenizer.padding_side = 'left'; inputs = tokenizer(texts, padding=True, truncation=True, return_tensors='pt')`
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For generation, use a pipeline with `tokenizer.padding_side = 'left'` and set `pad_token_id=tokenizer.eos_token_id` if no pad token is defined.
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If using Trainer, set `tokenizer.padding_side = 'left'` in the data collator or before creating the dataset to ensure all batches are left-padded.
无效尝试
常见但无效的做法:
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80% 失败
The model will generate incorrect tokens because it attends to padding tokens at the end, especially for left-to-right generation tasks like text completion.
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60% 失败
The tokenizer's padding_side only affects future calls to tokenizer(); if you already tokenized the input, the padding direction is already set and won't change.
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50% 失败
This only sets the pad token ID; it does not change the padding direction, so the warning and incorrect behavior persist.