Manas-64M · GRPO

The SFT model trained with GRPO: 6 samples per prompt, scored by Skywork-Reward-V2-Qwen3-0.6B, advantages relative to the group mean, no critic.

Try it: chat Space · Every stage: collection · Code: github.com/kuluruvineeth/manas · Data: manas_dataset

Results

first 3 log points last 3 log points
mean reward -2.21 -1.50
KL to the SFT reference 0.003 0.005
response length (tokens) 257 141

600 steps in 60 minutes, one log point every 50 steps. Each point is a small batch, so read the trend, not single values. Responses got shorter as the reward rose; part of the gain may be the reward model preferring short answers.

training curves

Benchmarks

Zero-shot multiple choice, 500 items per task, scored by comparing answer log-likelihoods (scripts/evaluate.py).

benchmark accuracy random chance items
arc_challenge 21.4% 25.1% 500
arc_easy 32.6% 25.0% 500
hellaswag 34.6% 25.0% 500
mmlu 25.8% 25.0% 500
openbookqa 25.4% 25.0% 500
average 28.0%

A 64M model has far less capacity than these benchmarks assume, so scores sit near random chance. They are published because hiding them would be dishonest, and they move by about a point between stages, which is within noise at 500 items.

Use

from transformers import AutoModelForCausalLM, AutoTokenizer

repo = "kuluruvineeth/manas-64m-grpo"
tokenizer = AutoTokenizer.from_pretrained(repo)
model = AutoModelForCausalLM.from_pretrained(repo)

messages = [{"role": "user", "content": "What is the capital of France?"}]
inputs = tokenizer.apply_chat_template(messages, add_generation_prompt=True, return_tensors="pt", return_dict=True)
out = model.generate(**inputs, max_new_tokens=60, do_sample=False)
print(tokenizer.decode(out[0][inputs["input_ids"].shape[1]:], skip_special_tokens=True))

The export is a standard transformers checkpoint, so vLLM and SGLang load it with no custom code (vllm serve kuluruvineeth/manas-64m-grpo).

Training

  • Lineage: starts from manas-64m-full-sft.
  • Method: GRPO, 6 generations per prompt, β = 0.1 KL to the SFT reference, up to 512 new tokens, temperature 0.8.
  • Data: rlaif.jsonl: prompts only; completions are sampled during training (sources and licenses).
  • Trainer: trainer/train_grpo.py, peak learning rate 3e-7 (from the training log).
  • Hardware: one A100 or H100 GPU on Modal (gpu/modal_train.py).
  • Architecture: Qwen3 layout: 768 hidden, 8 layers, 8 query / 4 key-value heads (head dim 96), SwiGLU MLP of width 2,432, RoPE θ = 10⁶, tied embeddings, 6,400-token byte-level BPE vocabulary. 63,912,192 parameters.

Limitations

English only. At this size the model has little world knowledge: it is confidently wrong about facts that need it, loses the thread in long conversations, and should not be used for anything that matters. It is a teaching and research artifact for studying how each training stage changes a model.

Files

  • model.safetensors, config.json, tokenizer.json, chat_template.jinja: the transformers export
  • grpo_768.pth: the raw training checkpoint for the training code
  • grpo_768_metrics.jsonl, grpo_768_curves.png: the training log and its plot
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