Tree-Ising Repairs LLM Weights via Discrete Optimization, Outperforming Agent-Based Edits on MATH-500

·2026.11.11 22:32

Key point

The method uses simulated annealing on BF16 weights to fix reasoning loops in Qwen3.5-0.8B, requiring only $0.90 in GPU time and zero LLM tokens.

Details

  • Tree-Ising casts LLM weight repair as a sparse discrete optimization problem over BF16 weights, decomposing it into independent QUBO problems solved via simulated annealing or quantum-inspired simulated bifurcation.
  • On Qwen3.5-0.8B, the method achieves 54.6% on MATH-500, outperforming the GPT-6 Astra agent's 51.7% and the base model's 7.9%, while modifying 13% to 17% fewer weights and reducing bit flips by a factor of 2.2 to 2.3.
  • The approach requires only four forward-pass requests and zero LLM tokens, with the annealing recipe costing approximately $0.90 in GPU time.
  • On Qwen3.5-2B, the same recipe increases greedy GSM8K accuracy from 21.6% to 69.4% when layers and dose are selected using only the base model.
  • An eight-variable repair subproblem was executed using QAOA on an IBM Heron processor as a proof of concept.

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