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Scalable Influence and Fact Tracing for Large Language Model Pretraining
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Scales gradient-based training data attribution (TrackStar) to retrieve influential C4 pretraining examples for an 8B LLM over 160B tokens, combining optimizer second-moment correction, a task-specific mixed Hessian, and unit normalization, and compares attribution vs. influence on fact tracing.
Problem
Training data attribution has been hard to apply to the full scale of LLM pretraining (billions of parameters, hundreds of billions of tokens, thousands of queries), and it is unclear whether influential examples align with examples that entail a fact.
Approach
Refines gradient-based influence (TRAK/TracIn/EK-FAC-style) with per-parameter optimizer second-moment correction applied before random projection, a task-specific mixed Hessian approximation that downweights template-shared gradient components, unit normalization, and token-level loss gradients, enabling exact scoring over all of C4 without prefiltering.
Key results
- On T-REx closed set (8B model, 19.6M sentences), TrackStar reaches MRR 0.365 and tail-patch +0.90%, versus BM25 at MRR 0.592 and tail-patch +0.41%.
- On full C4 (365M examples), TrackStar achieves tail-patch +2.11% vs +0.83% for BM25 and +0.54% for Gecko, while BM25 has higher MRR (0.687 vs 0.338).
- Attribution (MRR) of TrackStar improves with model size and training tokens, so influence aligns more closely with factual attribution for larger models.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use TrackStar instead of BM25 | 8B model proponent retrieval · T-REx closed set | Tail-patch: +0.41% -> +0.90% | Helped |
| Use TrackStar instead of BM25 | 8B model proponent retrieval · C4 open set | Tail-patch: +0.83% -> +2.11% | Helped |
| Use BM25 instead of TrackStar | 8B model proponent retrieval · T-REx closed set | MRR: 0.365 -> 0.592 | Helped |
| Use BM25 instead of TrackStar | 8B model proponent retrieval · C4 open set | MRR: 0.338 -> 0.687 | Helped |
| Add unit normalization (ablation) | gradient-based retrieval · T-REx closed set | MRR: 0.064 -> 0.266 | Helped |
| Add task-specific Hessian approximation (ablation) | TrackStar · C4 open set | MRR: 0.252 -> 0.338 | Helped |
| Add task-specific Hessian approximation (ablation) | TrackStar · C4 open set | Tail-patch: +1.95% -> +2.11% | Helped |
| Add optimizer second moment correction (ablation) | gradient-based retrieval with unit normalization · T-REx closed set | MRR: 0.266 -> 0.300 | Helped |
| Combine optimizer correction with Hessian approximation (ablation) | gradient-based retrieval with unit normalization · T-REx closed set | MRR: 0.290 -> 0.295 | No clear effect |
| Use loss rather than margin output function (ablation) | TrackStar gradient computation · T-REx closed set | MRR: 0.293 -> 0.295 | Helped |
| Use loss rather than logit output function (ablation) | TrackStar gradient computation · T-REx closed set | Tail-patch: +0.71% -> +0.87% | Helped |
Surprising findings
- Classical BM25 retrieves entailing passages better than gradient methods but its proponents have much less influence on model predictions, showing a misalignment between attribution and influence.
- Applying the TRAK per-example Q correction instead of per-token drops MRR from about 0.122 to 0.001 at scale, so methods that work on small classification settings may fail at LLM scale.
Experimental setup
Datasets: C4 T-REx KILT COPA PIQA arithmetic word problems
Benchmarks: T-REx fact tracing C4 open set fact tracing COPA PIQA
Metrics: MRR Recall@10 tail-patch score
Baselines: BM25 Gecko TRAK Gradient cosine ablation Gradient dot product ablation
Builds on: TRAK TracIn EK-FAC LoGra Datamodels
Closest papers by meaning
- DATE-LM: Benchmarking Data Attribution Evaluation for Large Language Models (NeurIPS 2025 · similarity 0.89)
- Sketching the Readout of Large Language Models for Scalable Data Attribution and Valuation (NeurIPS 2026 · similarity 0.89)
- On Linear Representations and Pretraining Data Frequency in Language Models (ICLR 2025 · similarity 0.89)
- Fixing It in Post: A Comparative Study of LLM Post-Training Data Quality and Model Performance (NeurIPS 2025 · similarity 0.88)
- MATES: Model-Aware Data Selection for Efficient Pretraining with Data Influence Models (NeurIPS 2024 · similarity 0.88)
- MASS: Mathematical Data Selection via Skill Graphs for Pretraining Large Language Models (ICML 2025 · similarity 0.88)
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