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Scaling Test-Time Compute Without Verification or RL is Suboptimal

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arxiv 2502.12118 v2 pith:G7MHQXAT submitted 2025-02-17 cs.LG cs.CL

classification cs.LGcs.CL
keywords computetest-timemethodsscalingsearchtracesverificationapproaches
verification ladder T0 review T1 audit T2 compute T3 formal
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Despite substantial advances in scaling test-time compute, an ongoing debate in the community is how it should be scaled up to enable continued and efficient improvements with scaling. There are largely two approaches: first, distilling successful search or thinking traces; and second, using verification (e.g., 0/1 outcome rewards, reward models, or verifiers) to guide reinforcement learning (RL) and search algorithms. In this paper, we prove that finetuning LLMs with verifier-based (VB) methods based on RL or search is far superior to verifier-free (VF) approaches based on distilling or cloning search traces, given a fixed amount of compute/data budget. Further, we show that as we scale test-time compute (measured as the output token length) and training data, suboptimality of VF methods scales poorly compared to VB when the base pre-trained LLM presents a heterogeneous distribution over correct solution traces (e.g., different lengths, styles, etc.) and admits a non-sharp distribution over rewards on traces sampled from it. We formalize this condition using anti-concentration [Erd\H{o}s, 1945]. This implies a stronger result that VB methods scale better asymptotically, with the performance gap between VB and VF methods widening as test-time budget grows. We corroborate our theory empirically on both didactic and math reasoning problems with 3/8/32B-sized pre-trained LLMs, where we find verification is crucial for scaling test-time compute.

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Forward citations

Cited by 16 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Oracle Gap and Signal Fidelity: A Fixed-Pool Diagnostic for Test-Time Collaboration

    cs.CL 2026-07 conditional novelty 6.0 of 10

    Training-free LLM collaboration gains are bounded by the fixed pool's oracle gap and then by signal coverage, fidelity, and harm, measurable with a small labeled audit.

  2. Asking LLMs to Verify First is Almost Free Lunch

    cs.CL 2025-11 conditional novelty 6.0 of 10

    Prompting an LLM to first verify a random/trivial candidate answer before generating its solution consistently improves accuracy over chain-of-thought prompting at small extra token cost.

  3. Learn from What We HAVE: History-Aware VErifier that Reasons about Past Interactions Online

    cs.RO 2025-08 conditional novelty 6.0 of 10

    A history-aware verifier that scores candidate actions using past interactions cuts failure rates in ambiguous robot manipulation tasks compared to using the generator alone.

  4. e3: Learning to Explore Enables Extrapolation of Test-Time Compute for LLMs

    cs.LG 2025-06 conditional novelty 6.0 of 10

    e3 couples asymmetric skill chaining, negative-gradient RL, and a difficulty/budget curriculum so a 1.7B model extrapolates test-time compute to 2x its training budget and sets reported <2B state-of-the-art on AIME/HMMT 2025.

  5. Thinking vs. Doing: Agents that Reason by Scaling Test-Time Interaction

    cs.LG 2025-06 conditional novelty 6.0 of 10

    Scaling the number of interaction steps, trained via a curriculum over rollout horizon, improves web-agent task success and outperforms scaling per-step reasoning under fixed token budgets.

  6. Sample Complexity and Representation Ability of Test-time Scaling Paradigms

    cs.LG 2025-06 conditional novelty 6.0 of 10

    Best-of-n sampling provably needs about 1/Δ samples versus 1/Δ² for self-consistency, and a constructed Transformer can route among experts using verifier feedback to reach near-optimal final responses.

  7. Generalizable LLM Learning of Graph Synthetic Data with Post-training Alignment

    cs.LG 2025-06 conditional novelty 6.0 of 10

    Post-training alignment on synthetic graph data yields statistically significant gains on some real-world implicit-graph tasks, but gains are inconsistent and multi-step reasoning remains fragile.

  8. Test-Time Scaling for Small VLMs on Multilingual Visual MCQ

    cs.CL 2026-07 accept novelty 5.5 of 10

    On EXAMS-V, token budget and parseability dominate chain count, PRM-guided search, and selectors for small VLMs; the policy model itself yields the largest gain.

  9. RaC: Robot Learning for Long-Horizon Tasks by Scaling Recovery and Correction

    cs.RO 2025-09 conditional novelty 5.0 of 10

    Robot policies trained on human interventions that rewind to a familiar state and then correct the mistake achieve higher long-horizon success and better data efficiency than imitation on full demonstrations alone.

  10. OpenCodeReasoning-II: A Simple Test Time Scaling Approach via Self-Critique

    cs.CL 2025-07 conditional novelty 5.0 of 10

    A 2.5M-example code reasoning dataset with critique traces enables Qwen2.5-based models to surpass prior open-weight distilled models on LiveCodeBench via test-time self-critique selection.

  11. Revisiting Test-Time Scaling: A Survey and a Diversity-Aware Method for Efficient Reasoning

    cs.CL 2025-06 conditional novelty 5.0 of 10

    ADAPT, a diversity-aware prefix fine-tuning method, improves best-of-N sampling efficiency for a 1.5B reasoning model, reaching 80% accuracy at N=32 versus N=256 for the baseline.

  12. Faster and Better LLMs via Latency-Aware Test-Time Scaling

    cs.CL 2025-05 conditional novelty 5.0 of 10

    Test-time scaling should be tuned for wall-clock latency rather than token count; branches plus speculative decoding win under time budgets.

  13. Why Does Reasoning Length Converge? Unveiling the Underfitting-Overfitting Trade-off in Chain-of-Thought

    cs.AI 2025-09 reject novelty 4.0 of 10

    LLM chain-of-thought length converges to an optimum because of an underfitting-overfitting tradeoff, formalized in a continuous reasoning-space framework and tested with RL.

  14. Continuous Self-Improvement of Large Language Models by Test-time Training with Verifier-Driven Sample Selection

    cs.CL 2025-05 reject novelty 4.0 of 10

    A test-time training method that fine-tunes LoRA adapters on verifier-selected high-confidence pseudo-labels, reporting large gains on math benchmarks, but evaluated on the same queries it adapts on.

  15. Scaling over Scaling: Exploring Test-Time Scaling Plateau in Large Reasoning Models

    cs.AI 2025-05 reject novelty 2.0 of 10

    A probabilistic saturation model for test-time scaling is proposed and fitted to reasoning benchmarks, but the plateau 'prediction' is computed from the same per-problem data used to measure it.

  16. Risk-Guided Diffusion: Toward Deploying Robot Foundation Models in Space, Where Failure Is Not An Option

    cs.RO 2025-06

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