Sebastian Raschka, Qwen3 0.6B GRPO Experiment: Collapse to 0.4% at 100 Steps with KL Term, Achieves 47.4% Without It

·2026.10.28 08:30

Key point

Confirmed that removing the KL term is essential for preventing performance collapse and improving efficiency when training Qwen3 0.6B with GRPO.

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Details

  • Sebastian Raschka released an 11-hour video lecture and code demonstrating how to directly implement inference models using PyTorch
  • On the MATH-500 benchmark, the Qwen3 0.6B base model (15.2%) improved to 47.4% after 50 steps of GRPO training with the KL term removed
  • The original GRPO configuration (including the KL term) was observed to collapse to 0.4% performance after 100 steps of training
  • When applying inference-time scaling (CoT, self-consistency), the base model's accuracy rose to 52.0%, but the required time increased by 85 times
  • In the distillation process, teacher model data selection had a greater impact on results than the number of epochs
  • Distilling with one epoch of Qwen3 235B A22B data achieved 45.0%, with training possible in approximately 30 minutes on a single H100
  • The target audience is those proficient in Python and PyTorch, limited to tasks with mechanically verifiable solutions such as math problems
  • The code is available on GitHub under the Apache 2.0 license, permitting commercial use

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