synthetic-data-generation

name	synthetic-data-generation
description	Generates synthetic instruction-response training data using Self-Instruct, Evol-Instruct, and distillation from strong models via OpenAI/Anthropic APIs or vLLM batch inference. Use when creating instruction-tuning datasets, evolving seed tasks for complexity, filtering for quality and diversity, or generating domain-specific training data (code, math, reasoning). Do not use for human annotation pipeline design.
license	Apache-2.0
compatibility	{"clients":["openai-codex","gemini-cli","opencode","github-copilot"]}
metadata	{"owner":"codex","domain":"synthetic-data-generation","maturity":"draft","risk":"low","tags":["synthetic","data","generation","self-instruct","distillation"]}

Purpose

Generate high-quality synthetic instruction-response pairs at scale for fine-tuning LLMs. Covers Self-Instruct (bootstrapping from seed tasks), Evol-Instruct (iteratively evolving complexity), and distillation-based generation (using strong model outputs as training data). Includes quality filtering, deduplication, and formatting for training pipelines.

When to use this skill

Use this skill when:

• bootstrapping an instruction-tuning dataset from a small set of seed examples (Self-Instruct)
• evolving instructions for increasing complexity and diversity (Evol-Instruct / WizardLM approach)
• distilling outputs from a strong model (GPT-4, Claude) into training data for a smaller model
• generating domain-specific synthetic data: code, math, reasoning chains, or multi-turn conversations
• filtering and deduplicating generated data for training quality
• running batch inference with vLLM or API calls for large-scale generation

Do not use this skill when

• the task is fine-tuning on the generated data — prefer instruction-tuning
• the task is creating preference pairs for RLHF — prefer reward-modeling or safety-alignment
• the task is cleaning and labeling human-collected data — prefer data-cleaning-labeling

Operating procedure

1. Design seed tasks. Create 50–200 diverse, high-quality seed examples with instruction, input (optional), and output. Cover task types (QA, summarization, code, math), complexity levels (factual → multi-step reasoning), and target domains.
2. Generate via Self-Instruct. Prompt the teacher model with 3–5 seeds to generate new instruction-response pairs. Generate 5–10× the seed count per iteration. Filter and add high-quality outputs back as seeds for the next round.
3. Apply Evol-Instruct for complexity. Evolve existing instructions by adding constraints, deepening reasoning, increasing specificity, or adding edge cases. Run 2–4 evolution rounds. Discard incoherent outputs (filter by perplexity or LLM judge).
4. Distill from strong models. For highest quality, generate responses using a frontier model:

   from openai import OpenAI
   client = OpenAI()
   response = client.chat.completions.create(
       model="gpt-4o",
       messages=[{"role": "user", "content": instruction}],
       temperature=0.7,
       max_tokens=2048,
   )
   

   For batch generation at scale, use vLLM offline inference:

   from vllm import LLM, SamplingParams
   llm = LLM(model="meta-llama/Llama-3.1-70B-Instruct")
   params = SamplingParams(temperature=0.7, max_tokens=2048)
   outputs = llm.generate(prompts, params)
   

5. Filter for quality. Apply multi-stage filtering:
   • Deduplication: MinHash or embedding-based near-duplicate removal (>0.85 cosine similarity)
   • Coherence: Discard responses that don't address the instruction (use a classifier or LLM judge)
   • Length filtering: Remove very short (<20 tokens) or excessively long responses
   • Safety filtering: Remove toxic, biased, or harmful content with a safety classifier
   • Consistency: Generate 2–3 responses per instruction, keep only those with consistent information
6. Format for training. Convert to the target chat template (ChatML, Llama, etc.):
   Save as JSONL. Include metadata: generation model, temperature, timestamp, and quality scores.

Decision rules

• Use Self-Instruct when starting from scratch with limited seed data (<200 examples).
• Use Evol-Instruct when the base dataset exists but lacks complexity or diversity.
• Use distillation when quality matters more than cost — frontier model outputs produce the best training signal.
• Prefer vLLM batch inference over API calls when generating >10K examples (10–100× cheaper).
• Always deduplicate before training — duplicate examples cause memorization and reduce generalization.
• If generating code data, validate syntax by attempting to parse (AST parsing for Python, compilation for compiled languages).
• For math data, verify answers with a symbolic solver or separate model before including.

Output requirements

1. Dataset Manifest — total examples, category distribution, generation method per subset, and quality filter pass rates
2. Seed Task Documentation — the seed examples used, diversity analysis, and coverage gaps
3. Quality Report — deduplication rate, coherence filter rejection rate, sample quality audit results
4. Training-Ready Files — JSONL formatted data with chat template applied, split into train/validation

References

Read these only when relevant:

• Wang et al., "Self-Instruct: Aligning Language Models with Self-Generated Instructions"
• Xu et al., "WizardLM: Empowering Large Language Models to Follow Complex Instructions" (Evol-Instruct)
• Taori et al., "Stanford Alpaca: An Instruction-following LLaMA Model"
• vLLM offline inference: https://docs.vllm.ai/en/latest/getting_started/examples/offline_inference.html
• OpenAI Batch API: https://platform.openai.com/docs/guides/batch

Related skills

• instruction-tuning — fine-tuning on the generated data
• data-cleaning-labeling — cleaning and annotating raw human data
• eval-dataset-design — creating evaluation sets (not training data)
• reward-modeling — generating preference pairs for RLHF

Failure handling

• If generated instructions are repetitive despite diverse seeds, increase temperature (0.8–1.0) and add explicit diversity prompts ("Generate a task different from all previous ones").
• If quality filter rejects >50% of generated data, the teacher model or prompt template is poor — revise the generation prompt before scaling up.
• If Evol-Instruct produces incoherent outputs after 2+ rounds, cap evolution depth and use the last coherent version.
• If API rate limits block large-scale generation, switch to vLLM batch inference with an open-weight model or use the OpenAI Batch API (50% cost reduction, 24-hour turnaround).