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[SFT] Add seq_lengths to signature columns #3699

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Merged
merged 3 commits into from
Jul 8, 2025
Merged

[SFT] Add seq_lengths to signature columns #3699

merged 3 commits into from
Jul 8, 2025

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LeonEricsson
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@LeonEricsson LeonEricsson commented Jul 6, 2025 •
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What does this PR do?

To avoid cross-contamination when training with packed sequences, we pass position_ids to FA2. This was introduced in PR #3526, which calculated position_ids during packing and added them to the dataset. To ensure these are retained, position_ids must be set as a signature column; otherwise, the Trainer will discard them as unused.

https://github.com/huggingface/transformers/blob/ca7e1a3756c022bf31429c452b2f313f043f32de/src/transformers/trainer.py#L1007

While this was implemented correctly, PR #3649 introduced an optimized approach where position_ids are computed within the data collator using a new dataset column, seq_lengths. However, the latter PR failed to update the signature column from position_ids to seq_lengths. As a result, seq_lengths is not passed to the collator, causing it to behave as if the sequences are not packed.

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@LeonEricsson LeonEricsson requested review from lewtun and kashif July 6, 2025 13:11
@LeonEricsson LeonEricsson added 🏋 SFT Related to SFT and removed 🏋 SFT Related to SFT labels Jul 7, 2025
@kashif kashif mentioned this pull request Jul 8, 2025
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@LeonEricsson
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LeonEricsson commented Jul 8, 2025 •
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waiting to merge until we've confirmed this fixes the issues raised in #3705

qgallouedec
qgallouedec approved these changes Jul 8, 2025
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Good!

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jiosephlee commented Jul 8, 2025 •
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if args.use_liger_kernel:
    dataset = dataset.select_columns(
        {"input_ids", "position_ids", "completion_mask"}.intersection(dataset.column_names)
    )

This line of code may need to be adjusted as well (edit: nvm just saw the new commit)

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kashif commented Jul 8, 2025

@jiosephlee fixed and tested and works thanks!

@kashif kashif merged commit 0462dd7 into huggingface:main Jul 8, 2025
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marcandrelarochelle pushed a commit to marcandrelarochelle/trl that referenced this pull request Jul 29, 2025
@LeonEricsson @kashif @marcandrelarochelle
[SFT] Add seq_lengths to signature columns (huggingface#3699)
15d7a0f 
Co-authored-by: Kashif Rasul <kashif.rasul@gmail.com>
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@kashif kashif kashif approved these changes

@qgallouedec qgallouedec qgallouedec approved these changes

@lewtun lewtun Awaiting requested review from lewtun

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@LeonEricsson @HuggingFaceDocBuilderDev @jiosephlee @kashif @qgallouedec