Non-Deterministic Behavior

Non-Deterministic Behavior

Why your prompt works today but fails tomorrow.

Non-Deterministic Behavior

LLMs are probabilistic machines. If you ask the same question twice, you might get two different answers.

The Temperature Effect

At temperature=0, the model is mostly deterministic, but floating point drift on GPUs can still cause minor variations. At temperature=1, the model takes creative liberties.

graph LR
    Input[Input Prompt] --> LLM{LLM}
    LLM -- "Run 1" --> OutputA[Output A: Correct]
    LLM -- "Run 2" --> OutputB[Output B: Hallucination]
    LLM -- "Run 3" --> OutputC[Output C: Refusal]
    
    style OutputB fill:#ffcdd2,stroke:#d32f2f
    style OutputA fill:#c8e6c9,stroke:#2e7d32

The Chain Reaction

In a linear chain A -> B -> C, a small variation in A becomes a large deviation in B, and a complete failure in C.

  • Step 1: "Summarize this." -> (Variation: Skips a key detail).
  • Step 2: "Extract entities from summary." -> (Misses the entity entirely).
  • Step 3: "Look up entity in DB." -> Crash.

Graph structures help mitigate this by adding validation loops (if C crashes, go back to A), treating non-determinism as a feature to be managed rather than a bug to be feared.

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