Understanding top_p in OpenAI API: From Safe to Creative Outputs

๐Ÿ” What is top_p?

top_p controls how many tokens (words or pieces of words) the model considers when generating the next word. It uses a technique called nucleus sampling.

  • top_p: 1 โžœ The model considers all possible tokens.
  • top_p: 0.8 โžœ The model only considers the top tokens whose cumulative probability adds up to 80%.

๐Ÿง  Example:

Letโ€™s say the model is trying to predict the next word. Here’s a simplified list of possible words and their probabilities:

WordProbability
happy0.4
joyful0.3
glad0.1
sad0.08
upset0.05
furious0.03
others0.04

With different top_p settings:

  • top_p: 1
    • All of these tokens are included in the selection pool.
    • The model can choose even rare, unexpected, or creative words.
    • Output is more diverse, but sometimes less predictable.
  • top_p: 0.8
    • Only the top tokens (happy, joyful, glad) are considered.
    • Output will be more focused, safer, and more expected.

๐Ÿค” top_p vs temperature

ParameterWhat it controlsTypical rangeBehavior
top_pSampling pool (limits candidate tokens)0.8โ€“1Lower = safer
temperatureSampling randomness (how “creative”)0.2โ€“1Lower = more focused

๐Ÿ“Œ Best practice: Change either top_p or temperature, not both at the same time (unless you know what youโ€™re doing).


โœ… When to use what?

GoalRecommended setting
Precise, safe, professional outputtop_p: 0.8
Creative, diverse, surprising outputtop_p: 0.9โ€“1
Random fun text (e.g. poetry, ideas)top_p: 1, temperature: 0.9โ€“1.2

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