Beebey/smallcoder-303m

🧠 SmallCoder (303M)

SmallCoder is a 303M parameter LLaMA-style language model trained from scratch for code generation and algorithmic reasoning.

This checkpoint represents a 6B-token Supervised Fine-Tuning (SFT) run that fixed a critical End-of-Sequence (EOS) token bug from earlier versions.

Despite its compact size, SmallCoder achieves state-of-the-art (SOTA) coding performance for <500M models, rivaling 1B–7B parameter LLMs.

Trained with support from Google’s TPU Research Cloud (TRC) program.

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🚀 Key Results

Model	Size	HumanEval (pass@1)	MBPP (pass@1)
SmallCoder (Stage 4.1)	303M	27.4 %	31.0 %
TinyLlama-1.1B	1.1B	~26.4 %	~27.6 %
MPT-1B-Instruct	1.0B	~22.0 %	~25.0 %
Zephyr-1.3B-SFT	1.3B	31.0 %	34.0 %
Mistral-7B-Base	7B	30.5 %	47.5 %

⚖️ SmallCoder nearly matches Mistral 7B on HumanEval while being 23× smaller.

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🧬 Model Architecture

A LLaMA-type causal decoder with standard Multi-Head Attention (MHA).

LlamaConfig(
  vocab_size=49152,               # StarCoder tokenizer
  hidden_size=768,
  num_hidden_layers=24,
  num_attention_heads=8,
  num_key_value_heads=8,
  intermediate_size=3072,
  max_position_embeddings=1024,
)

Parameter	Value
Total parameters	≈ 303 M
Context length	1 024 tokens
Tokenizer	bigcode/starcoder
Architecture type	LLaMA (MHA, non-GQA)
Precision	bfloat16
Optimizer	AdamW XLA
Hardware	TPU v4-32 (TRC)

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📚 Training Curriculum (4 Stages, 29.8B tokens)

Stage	Tokens (B)	Dataset	Objective	Loss ↓
1. Linguistic Base	6.3	FineWeb-Edu	General English grounding	10.87 → 2.58
2. Code Specialization	7.5	60 % Nemotron Synthetic Code / 40 % StarCoderData	Code syntax & reasoning	5.00 → 1.25
3. Math & Knowledge	10.0	Nemotron CC-Math / FineWiki / OpenWebMath	Mathematical reasoning	2.77 → 1.55
4.1 SFT (EOS Fixed)	6.0	Nemotron SFT / OpenCodeInstruct / OpenMathInstruct-2	Instruction-tuned code alignment	1.73 → ~0.70

🧩 Total ≈ 29.8 B tokens of curated curriculum learning.

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📊 Detailed Benchmarks (Stage 4.1 SFT)

Domain	Benchmark	Metric	Score
Code	HumanEval (0-shot)	pass@1	27.4 %
Code	MBPP (3-shot)	pass@1	31.0 %
Math	GSM8k (0-shot)	exact match	4.55 %
Knowledge	Wikitext-2	perplexity ↓	167.6
Reasoning	ARC (Easy/Challenge)	acc norm	34.6 / 22.8 %
Commonsense	HellaSwag	acc norm	28.3 %

humaneval/mbpp were computed with manual evaluation (max_new_tokens=512, temp=0.2) due to SFT format truncation issues in lm-eval.

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⚠️ Known Limitations

1. Code-Specialized Model Tuned for Python and algorithmic reasoning. Poor performance on general text, math, and commonsense tasks.

2. Short Context Trained on 1 024-token sequences only. Performance degrades on longer inputs.

3. Tokenizer Bias Uses bigcode/starcoder BPE vocabulary — optimized for code, not prose.

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💻 Usage Example

import torch
from transformers import AutoTokenizer, AutoModelForCausalLM

model_id = "Beebey/smallcoder-303m"
device = "cuda" if torch.cuda.is_available() else "cpu"

tokenizer = AutoTokenizer.from_pretrained(model_id)
model = AutoModelForCausalLM.from_pretrained(model_id, torch_dtype=torch.bfloat16).to(device)

prompt = """User: Write a Python function to compute Fibonacci numbers.
Assistant:"""
inputs = tokenizer(prompt, return_tensors="pt").to(device)

with torch.no_grad():
    outputs = model.generate(
        **inputs,
        max_new_tokens=512,
        eos_token_id=tokenizer.eos_token_id,
        pad_token_id=tokenizer.eos_token_id,
    )

print(tokenizer.decode(outputs[0], skip_special_tokens=True))

💡 Trained using the “User:” / “Assistant:” dialogue format.

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🧾 Citation

If you use SmallCoder (303M) in your research, please cite:

@misc{smallcoder303m,
  title  = {SmallCoder: A 303M-parameter Code LLM trained from scratch},
  author = {Da Silva, Ilan},
  year   = {2025},
  url    = {https://huggingface.co/Beebey/smallcoder-303m},
  note   = {Trained with Google TPU Research Cloud (TRC) support}
}

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🙏 Acknowledgements

This model was trained with support from the Google TPU Research Cloud (TRC) program. Special thanks to the open datasets that enabled this work: FineWeb, StarCoderData, Nemotron, and OpenWebMath.

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🧩 Summary

Category	Description
Type	Code LLM (LLaMA-style)
Parameters	303 M
Training tokens	~29.8 B
Specialty	Code generation & reasoning
Context window	1 024 tokens
Tokenizer	bigcode/starcoder
License	Apache 2.0
Hardware	TPU v4 (TRC Program)

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🔬 SmallCoder (303M) demonstrates that a carefully designed <500M model can achieve near-SOTA coding performance, matching 1B-class models on HumanEval — proving that efficient, compact, open models still matter.