tinymixtral-v1.1-0.5b β€” 0.5B-class MoE

Dense-ish small MoE (~432M total / ~176M active, top-2 of 6 routed experts) trained on the SmolLM-inspired blend β€” the "data quality" ablation that replaced C4 with FineWeb-Edu + Cosmopedia v2.

The repository name says "0.5b" (storage/coarse size class); the trained model is ~432M total parameters, of which ~176M are active per token.

Model details

Parameter Value
Type Sparse MoE, 6 routed experts (top-2)
Total params ~432M
Active params ~176M
Hidden size 896
Layers 10
Attention GQA 14 Q / 2 KV heads (head dim 64)
Vocab 32,000
Context 2,048

Training

  • Data: FineWeb-Edu + Cosmopedia v2 β‰ˆ 89:11 (sampling weights 36:4), 4B tokens.
  • LR: 7e-4 (swept over {1e-4, 3e-4, 5e-4, 7e-4} on 100M-token runs; 7e-4 best).
  • Batch: 24 Γ— 1024; cosine schedule with 2,000-step warmup.
  • Tokenizer: TinyLlama (32k SentencePiece).

Evaluation

Measured with lm-evaluation-harness v0.4.12, 0-shot (cuda, bf16).

Task Metric v1.1 (432M)
HellaSwag acc_norm 0.308
PIQA acc 0.616
WinoGrande acc 0.524
ARC-Easy acc 0.456
ARC-Challenge acc_norm 0.247
OpenBookQA acc_norm 0.288
BoolQ acc 0.606
LAMBADA acc 0.227
Mean β€” 0.409

Comparison with similar models

Same suite and settings, measured locally (lm-evaluation-harness v0.4.12, 0-shot, cuda, bf16):

Task Metric v1.1 (432M) SmolLM2-360M Qwen3-0.6B
HellaSwag acc_norm 0.308 0.563 0.473
PIQA acc 0.616 0.719 0.673
WinoGrande acc 0.524 0.587 0.563
ARC-Easy acc 0.456 0.705 0.609
ARC-Challenge acc_norm 0.247 0.383 0.340
OpenBookQA acc_norm 0.288 0.372 0.316
BoolQ acc 0.606 0.620 0.643
LAMBADA acc 0.227 0.532 0.401

SmolLM2-360M was trained on 4T tokens and Qwen3-0.6B on 36T tokens, versus 4B tokens for v1.1 (~1000Γ— less) on a single consumer GPU β€” the gap is primarily a data-budget difference.

The C4 β†’ SmolLM data-quality switch mainly improved ARC-Easy (+3.4pp) and BoolQ (+2.7pp) versus the legacy v1.0 C4 model (mean 0.403 β†’ 0.409); ARC-Challenge was unchanged (0.247).

Usage

from transformers import AutoModelForCausalLM, AutoTokenizer

model = AutoModelForCausalLM.from_pretrained("mikecovlee/tinymixtral-v1.1-0.5b", trust_remote_code=True)
tokenizer = AutoTokenizer.from_pretrained("mikecovlee/tinymixtral-v1.1-0.5b")

Requires transformers and trust_remote_code=True (custom tinymixtral architecture).

Limitations

  • Base model only: no instruction tuning or safety alignment.
  • Trained on only 4B tokens; English-centric. Superseded by v3.0.

Family

Naming. The MoE family is published under tinymixtral; the dense 276M iso-active ablation companions use the tinymistral spelling. Both belong to the same project.

Citation

@misc{tinymixtralv1.10.5b2026,
  title  = {TinyMixtral: a small Mixture-of-Experts language-model family},
  author = {Michael Lee},
  year   = {2026},
  howpublished = {\url{https://huggingface.co/mikecovlee/tinymixtral-v1.1-0.5b}}
}

License

MIT (Copyright (C) 2026 Michael Lee).

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