YarnBetaFast
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YarnBetaFast is the “fast” boundary of YaRN’s correction range — the position-dimension index below which no correction is applied. Relevant only when RopeScalingType is Yarn.
Quick reference
| Type | float? |
| Default | null (use model default) |
| Range | Typical 30 – 50 (dimension index) |
| Category | YaRN position encoding |
| Field on | ContextParameters.YarnBetaFast |
What it does
YaRN applies different treatment to different RoPE dimensions based on their frequency (wavelength). Below YarnBetaFast, positions are treated with raw extrapolation (no correction). Between YarnBetaFast and YarnBetaSlow, YaRN blends the two regimes.
null— use model default (typical value in YaRN papers is32).- Specific float — override.
Rarely touched. The model’s metadata carries sensible values.
When to change it
| Scenario | Value |
|---|---|
| Default | null |
| Research / YaRN tuning | Per paper recipe |
Example
// Default — do not override.
var preset = new Llama32Preset();
preset.ContextParameters.RopeScalingType = RopeScalingType.Yarn;
Interactions
RopeScalingType— must beYarn.YarnBetaSlow— upper boundary of the blend range.
What’s next
- YarnBetaSlow — companion upper boundary.
- Context parameters hub — all context knobs.