ResearchResearch paperLarge Language Models1 source · Oct 14, 2026

AFCS: Atomic-Fact-Conditioned Synthesis for Factual Knowledge Pretraining

We propose AFCS (Atomic-Fact-Conditioned Synthesis), a pipeline that first extracts source-supported atomic facts and then uses each retained fact to drive generation.

Key points

  • Synthetic data is increasingly used in language-model pretraining.
  • Existing knowledge-corpus synthesis pipelines, including WRAP and Nemotron-CC, usually take a source passage or document segment as input and generate rewritten or QA-style samples from that text.
  • In continued-pretraining experiments with OLMo-3-7B and a 32B base on the same FineWiki source corpus, AFCS outperforms WRAP and Nemotron-CC on SimpleQA, SimpleQA Verified, PopQA, and HotpotQA.
  • Granularity ablations show that fact-level synthesis improves over chunk-level, paragraph-level, and entity-level synthesis; and a 100B-token mid-training integration improves factual benchmarks and raises the 12-task general benchmark average by +1.09.

Sources (1)

  • [1]AFCS: Atomic-Fact-Conditioned Synthesis for Factual Knowledge Pretraining
    arXiv (AI, ML, NLP, CV, robotics, multi-agent) · Oct 14, 12:24 PM
    We propose AFCS (Atomic-Fact-Conditioned Synthesis), a pipeline that first extracts source-supported atomic facts and then uses each retained fact to drive generation.
    Synthetic data is increasingly used in language-model pretraining.

Extractive summary: sentences quoted from the sources.

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