AI Glossary Term

What does “Repetition Penalty” mean?

Definition

A decoding setting that lowers the probability of tokens the model has already produced to reduce loops.

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How Repetition Penalty works

Diagram for Repetition Penalty, steps in order: Model has already written 'very very'; then Penalty lowers probability of repeating those tokens; then Different word is more likely; then Less looping text.Model has already written 'very very'Penalty lowers probability ofrepeating those tokensDifferent word is more likelyLess looping text

Example

Without a penalty, a model might loop with 'the best of the best of the best'. A modest penalty on repeated tokens nudges it to move on.

Why it matters

Repetition loops make text unreadable. Too strong a penalty can stop the model from reusing words it legitimately needs, such as names.

Common questions

Repetition vs frequency penalty?

They are similar. Frequency penalty scales with how many times a token appeared; repetition penalty is often applied once to any seen token.

Typical values?

Slightly above 1 in some systems; scales differ by software, so check the documentation.

Does it fix all loops?

Not always. It helps with simple loops but can distort legitimate repeats.

Related terms

Frequency PenaltyA decoding setting that reduces the probability of tokens proportionally to how often they've appeared so far.Presence PenaltyA decoding setting that reduces the probability of tokens that have appeared at all, encouraging new topics.Top-k SamplingA decoding strategy that samples only from the k most likely next tokens.Guarded DecodingA generation strategy that constrains output tokens to valid structures or policy-compliant choices.Speculative DecodingAn inference acceleration method where a small draft model proposes tokens that a larger model verifies in parallel.Sliding Window AttentionAn attention pattern where each token attends only to a fixed-size window of nearby tokens to reduce compute.

Learn more in our free guides

Repetition Penalty and Decoding ControlsAI Flashcards and Spaced Repetition

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Repetition Penalty and Decoding Controls QuizAI Flashcards and Spaced Repetition Quiz

See also

Beam SearchParent-Document RetrievalMulti-Query RetrievalRAG-FusionSelf-PlayPost-trainingMid-trainingWatermarking