BioCompute-ARB-Qwen3-8B-GRPO

Qwen3-8B trained to act as a tool-using research agent on BioCompute-ARB, a small Auto Research Benchmark for scientific computing in computational biology (pairwise alignment with affine gaps, stiff reaction-network simulation, SEIR change-point inference). Each task is graded by an independent program on hidden test cases.

Code, benchmark tasks, training scripts and evaluation logs: https://github.com/sc2musa/BioCompute-ARB-Qwen3-8B-GRPO

Training

  1. Rejection-sampling fine-tuning (RFT). Qwen3-8B generated agent trajectories on freshly generated training instances (new seeds; the benchmark's hidden test cases were never used). Trajectories were sampled with method guidance, scored by the task grader, and the kept ones were trained on with the goal-only instruction (guidance removed). Full-parameter, 3587 turn samples from the reaction-network task, 2 epochs, lr 1e-5.
  2. Multi-turn agentic GRPO with ROLL, starting from the RFT model: 4 attempts per training instance, turn-level samples sharing the episode return (score + 0.5 if solved), group-normalised advantages, no KL, lr 1e-6, 32 trajectories per step, 60 steps on 256 alignment and reaction-network training instances. This is the final checkpoint.

No teacher model or human-written solutions were used.

Results (held-out test set, 20 trials per task)

Configuration F: goal-only instruction, non-thinking mode, repeat guard, public self-check script.

Model Reaction network: solved / mean score Alignment: mean score SEIR: mean score
Qwen3-8B 0/20 / 0.656 0.154 0.031
+ RFT 11/20 / 0.550 0.047 0.000
+ RFT + GRPO (this model) 19/20 / 0.950 0.068 0.000

Usage

Use non-thinking mode (enable_thinking=False) with tool calling, e.g. vLLM:

vllm serve SC2meisah/BioCompute-ARB-Qwen3-8B-GRPO --enable-auto-tool-choice \
  --tool-call-parser hermes --reasoning-parser qwen3 --max-model-len 40960

and the agent harness of the benchmark repository (harness/runner.py --agent llm --guidance goal --repeat-guard --public-check), sampling with temperature 0.7, top_p 0.8.

Limitations

  • The improvement is concentrated on the reaction-network task, where the base model already succeeded occasionally. No model solves the alignment or SEIR tasks; the alignment score is below the base model.
  • With thinking mode enabled the model often writes the program inside its reasoning and submits without writing the file (10/20 on the reaction-network task instead of 19/20).
  • Evaluated with 20 trials per task on one benchmark; test instances come from the same generators as the training instances (different seeds), so out-of-distribution generalisation is untested.
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