Results
Table with columns: metric, gpt2-muon (this), GPT-2 124M, nanoGPT / llm.c 124M (AdamW)| metric | gpt2-muon (this) | GPT-2 124M | nanoGPT / llm.c 124M (AdamW) |
|---|
| val_loss (FineWeb-Edu val shard) | 2.9653 | ~3.29 | 3.28 |
| HellaSwag (acc_norm) | 0.3238 | 0.294 | ~0.30 |
| HellaSwag (acc) | 0.2991 | — | — |
| LAMBADA (acc / ppl) | 0.2826 / 27.81 | ~0.33 / ~35 | — |
Protocol note. val_loss is 2.9653 scored on the full 100M-token FineWeb-Edu
validation shard. An earlier version of this card reported 2.99, which was the
in-training figure computed on a 10.5M-token prefix — the harness counted validation
micro-batches rather than tokens, so the budget depended on batch and world size. Absolute
val_loss is protocol-sensitive; always compare on a matched window.
Evaluated with Karpathy's exact HellaSwag method (10,042 val examples), on the same data, val shard, and tokenizer as the references. The Muon+WSD recipe clearly beats the AdamW+cosine reference on val_loss and HellaSwag at matched data and scale.
Compared head-to-head against a modern architecture
This model is rung 2 of a three-rung ladder. Rung 3,
muteptr/skyai-modern-xs, keeps the
tokenizer, data, token budget, and schedule shape identical and changes only the
architecture (RMSNorm, RoPE, SwiGLU, GQA, QK-norm, untied embeddings, logit soft-cap). On a
matched 100M-token validation shard it reaches 2.9548 vs 2.9653 here (+0.0104 nats,
paired 95% CI [+0.0102, +0.0107]) and LAMBADA ppl 26.25 vs 27.81, at ~8% fewer
FLOPs/token — while being statistically tied on all accuracy benchmarks.
Caveats (read these)
- Recipe-level, not Muon in isolation — Muon, WSD, and tuned LRs/weight-decay moved together; the WSD decay-to-zero contributes a real share of the val-loss margin.
- Single seed.
- val_loss vs GPT-2 is home-field — this model trained on FineWeb-Edu and GPT-2 did not, so the neutral comparison is HellaSwag.
- Base model, not instruction-tuned, and trained on educational text — strongest on encyclopedic/explanatory prompts.
Usage
import torch
from transformers import AutoModelForCausalLM, AutoTokenizer
tok = AutoTokenizer.from_pretrained("muteptr/gpt2-muon-124m")
model = AutoModelForCausalLM.from_pretrained("muteptr/gpt2-muon-124m").eval()
inputs = tok("Photosynthesis is the process by which", return_tensors="pt")
out = model.generate(**inputs, max_new_tokens=40, do_sample=True, top_k=50, temperature=0.8)
print(tok.decode(out[0], skip_special_tokens=True))
Sample output:
Photosynthesis is the process by which a plant absorbs carbon dioxide from the air, stores it in the soil, and uses the stored carbon to make its own food. The main function of Photosynthesis in a plant is to capture sun…
Training
Table | |
|---|
| Data | FineWeb-Edu sample-10BT (~10B tokens, gpt2 BPE) — 99 train shards + 1 val |
| Hardware | 8×A100-80GB SXM4, ~2.1h |
| Optimizer | Muon-split — Newton-Schulz orthogonalized momentum on 2D hidden matrices, AdamW on embeddings / norms / biases. Re-tuned for gpt2 (tied wte + LayerNorm): embedding_lr=0.006, matrix_lr=0.015, weight_decay=0.28 |
| Schedule | warmup-stable-decay — 715 warmup / 19,073 steps, LR decayed to 0 over the final 40% |
| Batch | 524,288 tokens/step (0.5M), context length 1024 |
|
Full, runnable recipe: configs/gpt2-muon.yaml.
License
MIT for the weights. Training data is FineWeb-Edu (ODC-BY).