PenaltyContextSize

PenaltyContextSize sets the number of recent tokens considered when applying repetition, presence, and frequency penalties. Only the last PenaltyContextSize tokens influence penalty calculations.

Quick reference


Type	`int`
Default	`-1` (use the model’s full context size)
Range	`-1` or positive integer
Category	Penalty window
Field on	`SamplerParameters.PenaltyContextSize`

What it does

Before each sampling step, the three penalty knobs (RepetitionPenalty, PresencePenalty, FrequencyPenalty) need to know which prior tokens to examine. PenaltyContextSize defines that window.

PenaltyContextSize = -1 — use the full context (equivalent to ContextParameters.ContextSize). Maximum recall; penalties apply across the entire conversation.
PenaltyContextSize = 256 — only the last 256 tokens contribute. Penalties are local; the model can freely reuse words that appeared earlier than that.
PenaltyContextSize = 64 — very local window; penalties essentially prevent immediate repetition only.

Narrow windows make penalties local (avoid recent verbatim repeats); wide windows make them global (avoid any mention of a token anywhere in history).

When to change it

Scenario	Value
Default — penalize repetition across full context	`-1`
Fresh-style writing that can revisit topics	`256` – `512`
Strict anti-repetition for short outputs	`128`
Very local penalty (only consecutive repeats)	`64`

Longer conversations may benefit from a smaller penalty window so the model isn’t punished for reusing common words across a long dialogue. For short-form answers, the default -1 is usually fine.

Example

var preset = new Qwen25Preset();
preset.SamplerParameters.PenaltyContextSize = 256;
preset.SamplerParameters.RepetitionPenalty = 1.15f;
// Discourage repetition within the last 256 tokens; older history doesn't trigger the penalty.

using var api = AsposeLLMApi.Create(preset);

Interactions

RepetitionPenalty — applied within this window.
PresencePenalty — same window.
FrequencyPenalty — same window.
ContextParameters.ContextSize — upper bound; at -1, PenaltyContextSize equals this.

What’s next

Sampler parameters hub — all sampler knobs at a glance.
RepetitionPenalty — the main penalty that uses this window.
Garbled output — repetition loops — when penalty tuning helps.

TopNSigma RepetitionPenalty