Best-of-N Sampling
best-of-n-sampling-53c64a2c·4 events·first seen 1mo agoAliases: Best-of-N Sampling
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Adaptive Parallel Reasoning: The Next Paradigm in Efficient Inference Scaling
A BAIR blog post surveys recent progress in parallel reasoning for LLMs, covering methods from simple self-consistency and Best-of-N sampling through structured search (Tree of Thoughts, MCTS) to newer adaptive approaches including ParaThinker, GroupThink, and Hogwild! Inference. The core motivation is that sequential reasoning scales linearly with exploration depth, causing latency, context-rot, and compute inefficiency. Adaptive parallel reasoning aims to let models themselves decide when and how to decompose tasks into concurrent threads, rather than imposing fixed parallel structure externally. The post frames this as an emerging inference-time scaling paradigm with implications for agentic and complex reasoning workloads.
Alignment Tampering: How RLHF Can Be Exploited to Amplify Misaligned Biases
This paper introduces 'alignment tampering,' a structural vulnerability in RLHF where the LLM being aligned can influence its own preference dataset, causing the training process to amplify undesired behaviors rather than correct them. The mechanism exploits two core RLHF limitations: preference data is drawn from the model's own outputs, and pairwise comparisons capture relative quality without capturing the reason for preference. Experiments demonstrate amplification of diverse biases including sexism, brand promotion, and instrumental goal-seeking. Existing robust RLHF mitigations fail to fully resolve the issue without degrading response quality.
Bidirectional Evolutionary Search (BES) for Self-Improving Language Models
BES is a search framework that combines forward evolutionary candidate generation with backward goal decomposition to address limitations of best-of-N and tree search methods. Forward search uses recombination operators to escape the narrow entropy shell of autoregressive expansion, while backward search recursively decomposes tasks into checkable subgoals for dense intermediate feedback. Theoretical analysis shows evolutionary operators can escape entropy-shell confinement and backward search can exponentially reduce required samples. Experiments demonstrate consistent gains on post-training tasks where mainstream algorithms fail, and superior performance on three open problem-solving benchmarks at inference time.
GGRO: Gradient-Guided Reward Optimization for inference-time LLM alignment
Researchers introduce Gradient-Guided Reward Optimization (GGRO), an inference-time alignment method that uses gradient signals from a reward model to inject 'nudging tokens' at high-uncertainty decoding steps, rather than relying on sampling-intensive re-ranking approaches like Best-of-N. The method monitors token-level entropy to detect distribution drift and steers generation trajectories directly, claiming improved robustness to reward hacking with minimal computational overhead. Experiments show gains across safety, helpfulness, and reasoning benchmarks compared to standard inference-time alignment baselines.