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Pretraining

As explained in Reinforcement Learning from Human Feedback

Pretraining is the initial large-scale optimization of a model on broad data, commonly through next-token prediction.

Pretraining is the large-scale phase that produces a base model with broad knowledge and capabilities through next-token prediction. Its output establishes most of the potential later cultivated by post-training. section 1.4

Next-token prediction does not automatically yield useful conversation. Post-training reshapes that behavior toward question-answering and attempts to expose capabilities that pretraining makes available but does not directly express. section 1.4

Pretraining establishes the starting point for later optimization:

  • Produces a static base model whose knowledge and capabilities constrain the final model’s potential. section 1.4
  • Leaves substantial performance gains to mid-training, high-quality end-of-pretraining data, instruction tuning, RLVR, and preference tuning. section 1.4

OLMoE comparison

OLMoE Instruct’s second version changed little in pretraining but improved its popular-benchmark average from 35 to 48 through post-training, illustrating the distinction between creating capability and eliciting it. section 1.4

How Reinforcement Learning from Human Feedback covers it

How deep it goes
Contrasts pretraining with post-training and next-token prediction, but does not detail datasets, optimization procedures, or model internals.
Examples
Uses the OLMoE Instruct version comparison to show how post-training can improve a mostly unchanged pretrained foundation.
What you can do after
Evaluate pretraining as capability creation and distinguish it from post-training’s elicitation of that capability.
How it connects
Connects pretraining to base models, next-token prediction, post-training, instruction tuning, RLVR, and preference tuning.

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Related concepts

This explainer was generated by Manning's knowledge graph from the text of Reinforcement Learning from Human Feedback. The section links point to the parts of the book it draws on.