Sample Where You Struggle: Sharpening Base Model Reasoning via Entropy-Guided Power Sampling
- URL: http://arxiv.org/abs/2606.09926v1
- Date: Sun, 07 Jun 2026 14:06:20 GMT
- Title: Sample Where You Struggle: Sharpening Base Model Reasoning via Entropy-Guided Power Sampling
- Abstract summary: Entropy-Guided Power Sampling (EGPS) is a training-free and verifier-free sampler.<n>EGPS skips deterministic blocks, localizes each MCMC move to a high-entropy neighborhood, and applies Multiple-Try Metropolis at decision points.
- Score: 7.8682919561927065
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Sampling from the sequence-level power distribution $p^α$ elicits RL-level reasoning from base language models without any parameter updates, but the standard Metropolis--Hastings (MH), a Markov Chain Monte Carlo (MCMC) sampler, is both expensive and slow-mixing. We trace both to a structural mismatch: $p^α$ mainly departs from $p$ at a sparse, spatially clustered set of high-entropy decision points, yet MH proposes resampling positions uniformly along the prefix -- wasting compute on near-degenerate conditionals while under-mixing precisely where modes diverge. We propose Entropy-Guided Power Sampling (EGPS), a training-free and verifier-free sampler that re-derives its proposal from token-level entropy already in the forward pass. EGPS skips deterministic blocks, localizes each MCMC move to a high-entropy neighborhood, and applies Multiple-Try Metropolis at decision points -- making sampling cost scale with \emph{entropy mass rather than sequence length}. On Qwen2.5-Math-7B, EGPS reaches best or tied-best accuracy on all three benchmarks (MATH500 $75.8\%$, HumanEval $62.2\%$, GPQA $42.4\%$) at up to a $12.6\times$ wall-clock speedup over the MH baseline.
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