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LLM Data Selection and Utilization via Dynamic Bi-level Optimization
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Proposes a Data Weighting Model (DWM) that reweights samples within each batch during LLM pretraining, learned via a multi-stage bi-level optimization that maximizes validation (LAMBADA) performance, improving randomly and carefully selected data.
Problem
Existing LLM data selection methods are static and training-agnostic, selecting data before training and using selected samples indiscriminately within batches, ignoring the dynamic data preference of the model and joint effects between samples.
Approach
A plug-and-play data weighting model that assigns per-sample weights within each batch (considering inter-sample interactions) and is updated across training stages by a bi-level objective that maximizes the validation performance of the LLM trained with those weights, with the weighting model transferable to other selection methods and model sizes.
Key results
- On 370M models with random data, RANDOM+DWM reaches 46.4 two-shot average vs 45.1 for RANDOM (and 48.5 for QuRating, 48.6 for QuRating+DWM at 370M).
- At 1.3B, QuRating+DWM improves two-shot average from 50.3 to 51.0 and RANDOM+DWM from 47.6 to 48.7 when weighting model transferred from 370M.
- Ablations show the dynamic multi-stage weighting outperforms static weighting from stage 1 or stage 4 and that using LAMBADA as validation beats held-out SlimPajama validation (46.4 vs 46.1 two-shot).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add DWM to random-selected data | 370M pre-training · 9 downstream tasks, two-shot | Average accuracy: 45.1 -> 46.4 | Helped |
| Add DWM to DSIR-selected data | 370M pre-training · 9 downstream tasks, two-shot | Average accuracy: 45.3 -> 46.4 | Helped |
| Add DWM to QuRating-selected data | 370M pre-training · 9 downstream tasks, two-shot | Average accuracy: 48.5 -> 48.6 | No clear effect |
| Add transferred DWM to random-selected data | 1.3B pre-training · 9 downstream tasks, two-shot | Average accuracy: 47.6 -> 48.7 | Helped |
| Add transferred DWM to DSIR-selected data | 1.3B pre-training · 9 downstream tasks, two-shot | Average accuracy: 48.7 -> 48.7 | No clear effect |
| Add transferred DWM to QuRating-selected data | 1.3B pre-training · 9 downstream tasks, two-shot | Average accuracy: 50.3 -> 51.0 | Helped |
| Use held-out SlimPajama validation data instead of LAMBADA (ablation) | DWM with random-selected data · 9 downstream tasks, zero-shot | Average accuracy: 45.0 -> 44.6 | Hurt |
| Use held-out SlimPajama validation data instead of LAMBADA (ablation) | DWM with random-selected data · 9 downstream tasks, two-shot | Average accuracy: 46.4 -> 46.1 | Hurt |
| Use 2 training stages instead of 5 (ablation) | DWM with random-selected data · 9 downstream tasks, two-shot | Average accuracy: 46.4 -> 45.3 | Hurt |
| Use 8 training stages instead of 5 (ablation) | DWM with random-selected data · 9 downstream tasks, two-shot | Average accuracy: 46.4 -> 46.5 | Helped |
| Use 2 training stages instead of 5 (ablation) | DWM with random-selected data · 9 downstream tasks, zero-shot | Average accuracy: 45.0 -> 44.3 | Hurt |
| Use 8 training stages instead of 5 (ablation) | DWM with random-selected data · 9 downstream tasks, zero-shot | Average accuracy: 45.0 -> 45.2 | Helped |
Surprising findings
- Using only the final-stage weighting model boosts early training but reduces diversity, leading to worse overall performance than dynamic weighting.
- The DWM gain for QuRating is minor at 370M but larger at 1.3B, which the authors attribute to model capacity absorbing high-quality reasoning data.
Limitations
- Gains are small on average (about 0.1 to 1.3 points) and mixed across tasks, with some tasks degrading.
- Performance drops in the stage-2 weighting model, so consistent improvement across all stages is not guaranteed.
- Only evaluated on LAMBADA as validation task and on small models up to 1.3B.
Experimental setup
Datasets: SlimPajama LAMBADA RedPajama
Benchmarks: ARC-easy ARC-challenge SciQ LogiQA BoolQ OpenbookQA HellaSwag PIQA WinoGrande
Metrics: accuracy normalized accuracy
Baselines: RANDOM DSIR QuRating RANDOM_60B
Builds on: DSIR QuRating DsDM MATES RegMix
Closest papers by meaning
- BLADE: Scalable Bi-level Adaptive Data Selection for LLM Training (NeurIPS 2026 · similarity 0.92)
- Rethinking Data Curation in LLM Training: Online Reweighting Offers Better Generalization than Offline Methods (ICLR 2026 · similarity 0.90)
- Dynamic Loss-Based Sample Reweighting for Improved Large Language Model Pretraining (ICLR 2025 · similarity 0.90)
- Get more for less: Principled Data Selection for Warming Up Fine-Tuning in LLMs (ICLR 2024 · similarity 0.89)
- Importance Weighting Can Help Large Language Models Self-Improve (AAAI 2025 · similarity 0.89)
- Data Selection via Optimal Control for Language Models (ICLR 2025 · similarity 0.89)
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