Synthetic Data Pipelines for LLM Post-Training: Generation, Quality Filtering, Deduplication, and Contamination Auditing
As frontier model post-training expands beyond the limits of human-annotated datasets, synthetic data generation (SDG) has become the core driver of alignment. Public disclosures from major research labs confirm that synthetic data now comprises the vast majority of tokens used in supervised fine-tuning (SFT) and preference alignment. For example, NVIDIA reported that over 98% of the data used in the alignment pipeline for Nemotron-4 340B was synthetically generated. Similarly, models across the
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