2nd/10_Wiki/Topics/AI_Sampling_Strategies.md

---
id: wiki-2026-0508-ai-sampling-strategies
title: AI Sampling Strategies
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [LLM Sampling, Decoding Strategies]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [llm, sampling, decoding, inference]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: python
  framework: vllm/transformers
---

# AI Sampling Strategies

## 매 한 줄
> **"매 logits → token 의 conversion 의 art — 매 quality vs diversity trade-off."** 매 greedy 의 deterministic — 매 temperature/top-k/top-p 의 stochastic — 매 2026 에 min-p, mirostat, speculative decoding 의 mainstream.

## 매 핵심

### 매 deterministic
- **Greedy**: argmax token. 매 repetitive 의 risk.
- **Beam search**: 매 top-B sequences 의 maintain. 매 translation 의 useful, 매 open-ended 의 bland.

### 매 stochastic
- **Temperature**: logits / T. T<1 sharpen, T>1 flatten.
- **Top-k**: 매 top-k tokens 의 sample.
- **Top-p (nucleus)**: 매 cumulative prob ≥ p 의 smallest set.
- **Min-p**: 매 P(top) * min_p 의 threshold — 매 top-p 의 better.
- **Typical-p**: 매 entropy-based — 매 typical tokens.
- **Mirostat**: 매 perplexity targeting feedback control.

### 매 응용
1. Creative writing — 매 high temp + top-p.
2. Code generation — 매 low temp + greedy fallback.
3. Reasoning — 매 self-consistency (sample N, majority vote).

## 💻 패턴

### Temperature + top-p
```python
import torch
import torch.nn.functional as F

def sample(logits, temperature=0.7, top_p=0.9):
    logits = logits / temperature
    probs = F.softmax(logits, dim=-1)
    sorted_probs, sorted_idx = probs.sort(descending=True)
    cumsum = sorted_probs.cumsum(-1)
    mask = cumsum - sorted_probs > top_p
    sorted_probs[mask] = 0
    sorted_probs /= sorted_probs.sum()
    pick = torch.multinomial(sorted_probs, 1)
    return sorted_idx.gather(-1, pick)
```

### Min-p
```python
def min_p_sample(logits, min_p=0.05, temperature=1.0):
    logits = logits / temperature
    probs = F.softmax(logits, dim=-1)
    threshold = probs.max(-1, keepdim=True).values * min_p
    probs = torch.where(probs >= threshold, probs, torch.zeros_like(probs))
    probs /= probs.sum(-1, keepdim=True)
    return torch.multinomial(probs, 1)
```

### Self-consistency (CoT majority vote)
```python
def self_consistency(prompt, llm, n=20):
    answers = []
    for _ in range(n):
        cot = llm.generate(prompt, temperature=0.7)
        answers.append(extract_final_answer(cot))
    from collections import Counter
    return Counter(answers).most_common(1)[0][0]
```

### Speculative decoding
```python
def speculative(target, draft, prompt, k=4):
    # Draft k tokens cheaply, target verifies in parallel
    ctx = prompt
    while not done(ctx):
        draft_tokens, draft_probs = draft.generate(ctx, k)
        target_probs = target.score(ctx, draft_tokens)
        accepted = []
        for i, (dp, tp) in enumerate(zip(draft_probs, target_probs)):
            r = torch.rand(1)
            if r < min(1, tp / dp):
                accepted.append(draft_tokens[i])
            else:
                # Reject, sample from (target - draft)+ then break
                resample = sample_diff(target_probs[i], draft_probs[i])
                accepted.append(resample)
                break
        else:
            accepted.append(target.sample(ctx + accepted))
        ctx += accepted
    return ctx
```

### Mirostat (perplexity control)
```python
def mirostat(logits, mu, tau=5.0, eta=0.1):
    # Adaptively adjusts top-k to target surprise tau
    sorted_probs, idx = F.softmax(logits, -1).sort(descending=True)
    s = -torch.log(sorted_probs)
    k = (s < mu).sum().item()
    k = max(k, 1)
    pick = torch.multinomial(sorted_probs[:k] / sorted_probs[:k].sum(), 1)
    surprise = -torch.log(sorted_probs[pick])
    mu = mu - eta * (surprise - tau)
    return idx[pick], mu
```

### Repetition penalty
```python
def apply_repetition_penalty(logits, generated_ids, penalty=1.1):
    for tok in set(generated_ids):
        if logits[tok] < 0:
            logits[tok] *= penalty
        else:
            logits[tok] /= penalty
    return logits
```

## 매 결정 기준
| 상황 | Sampler |
|---|---|
| Code, math, structured | T=0 greedy or T=0.2 |
| Chat / general | T=0.7, top-p=0.9 or min-p=0.05 |
| Creative / fiction | T=1.0+, min-p=0.02 |
| Reasoning ensemble | T=0.7, n=20, majority vote |
| Translation | Beam search (B=4-8) |
| Latency-critical | Speculative decoding (target + small draft) |

**기본값**: 매 T=0.7 + min-p=0.05.

## 🔗 Graph
- 부모: [[Decoding]]
- 응용: [[Self-Consistency]]
- Adjacent: [[LLM_Optimization_and_Deployment_Strategies|vLLM]]

## 🤖 LLM 활용
**언제**: 매 inference pipeline 의 every call — 매 task 의 sampler 의 match.
**언제 X**: 매 logprob analysis (no sampling needed).

## ❌ 안티패턴
- **High temp + greedy fallback**: 매 inconsistent — 매 single sampler.
- **Top-k=1 with high temp**: 매 contradictory.
- **No repetition penalty on long outputs**: 매 loops.
- **Speculative without acceptance check**: 매 distribution shift.

## 🧪 검증 / 중복
- Verified (Holtzman et al. nucleus sampling 2020, Leviathan et al. speculative 2023, min-p paper 2024).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — sampler taxonomy + working code |