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Sample, Scrutinize and Scale: Effective Inference-Time Search by Scaling Verification
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Shows that simply scaling a minimalist sampling-based search (random sampling plus Gemini self-verification with rewriting and pairwise tie-breaking) lets Gemini v1.5 Pro surpass o1-Preview on AIME, MATH, and LiveBench, and introduces a verification benchmark exposing weak out-of-box verification of frontier models.
Problem
Test-time compute scaling via sampling-based search depends on selecting the best candidate without ground-truth verifiers; it is unclear how performance scales with number of samples and verification effort, and how well models can self-verify.
Approach
Scale a minimalist sampling-based search with random sampling and LM self-verification (rewriting responses as theorem-lemma-proof, plus pairwise comparison tie-breaks), and identify implicit scaling: larger candidate pools improve verification accuracy on ambiguous questions.
Key results
- Gemini v1.5 Pro with Verification@200 reaches 8/15 on AIME 2024 and 135/200 on LiveBench Math, versus 1/15 and 104/200 for Pass@1 and 4/15 and 118/200 for Consistency@200; o1-Preview scores 7/15 on AIME in the table.
- Tie-breaking comparisons raise Verification@200 on MATH from 457/500 to 467/500 and LiveBench Reasoning from 94/140 to 97/140.
- On a verification benchmark, GPT-4o and Claude 3.5 Sonnet perform only marginally better than random guessing on comparison tasks, while o1-preview fails to identify 20-30% of wrong responses.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| use verification-based selection instead of majority-answer consistency | Gemini v1.5 Pro · AIME, MATH, LiveBench Math, and LiveBench Reasoning | accuracy: AIME: 4 / 15 -> 8 / 15; MATH: 460 / 500 -> 467 / 500; LiveBench Math: 118 / 200 -> 135 / 200; LiveBench Reasoning: 75 / | Helped |
| compare high-scoring candidate responses to break ties (ablation) | Gemini v1.5 Pro Verification@200 · MATH | accuracy: 457 / 500 -> 467 / 500 | Helped |
| compare high-scoring candidate responses to break ties (ablation) | Gemini v1.5 Pro Verification@200 · LiveBench Math | accuracy: 125 / 200 -> 135 / 200 | Helped |
| compare high-scoring candidate responses to break ties (ablation) | Gemini v1.5 Pro Verification@200 · LiveBench Reasoning | accuracy: 94 / 140 -> 97 / 140 | Helped |
| compare high-scoring candidate responses to break ties (ablation) | Gemini v1.5 Pro Verification@200 · AIME | accuracy: 7 / 14 -> 8 / 14 | Helped |
| rewrite candidate responses before verification (ablation) | Gemini v1.5 Pro verifier · MATH training split | false negative rate: 18% -> 17% | Helped |
| rewrite candidate responses before verification (ablation) | Gemini v1.5 Pro verifier · AIME 2023 | false negative rate: 12% -> 7% | Helped |
| set inference temperature to different tested values (ablation) | Gemini v1.5 Pro Verification@20 · MATH training split | accuracy: 82/100; 80/100; 79/100; 82/100 | No clear effect |
| set verification temperature to different tested values (ablation) | Gemini v1.5 Pro Verification@20 · MATH training split | accuracy: 76/100; 79/100; 79/100 | No clear effect |
| use Verification@200 instead of Consistency@200 | Gemini v1.5 Pro · LiveBench Olympiad | accuracy: 25.0% -> 22.7% | Hurt |
| use Verification@200 instead of Consistency@200 | Gemini v1.5 Pro · Flash model across AIME, MATH, LiveBench Math, and LiveBench Reasoning | accuracy: AIME: 3 / 15 -> 5 / 15; MATH: 440 / 500 -> 445 / 500; LiveBench Math: 92 / 200 -> 104 / 200; LiveBench Reasoning: 84 / 1 | Mixed |
Surprising findings
- Consistency@k saturates on AIME (Consistency@50 equals Consistency@10,000) while Verification@k keeps improving with power-law scaling.
- Frontier models including GPT-4o and Claude 3.5 Sonnet perform near random on the verification benchmark, and Consistency@5 often underperforms single-shot inference.
Limitations
- Each AIME result is a single run due to expense (about $200-650 per question), and the Olympiad LiveBench task shows no gain from verification.
- Verification relies on a closed Gemini model and LM-based answer scoring, with small benchmark sizes (e.g., 15 AIME questions).
- Prompts were explored only in a limited way and not optimized.
Experimental setup
Datasets: Berkeley MATH PRM800K AIME 2024 LiveBench MATH training split AIME 2023
Benchmarks: AIME 2024 Berkeley MATH LiveBench Math LiveBench Reasoning verification benchmark
Metrics: accuracy Pass@k Consistency@k Verification@k false positive rate false negative rate
Baselines: Consistency@200 Pass@1 o1-Preview Gemini v1.5 Flash GPT-4o Claude 3.5 Sonnet Gemini 2.0 Flash
Builds on: self-consistency chain-of-thought
Closest papers by meaning
- Test-Time Scaling in the Wild: Why Exploitation, Not Exploration, Is the Bottleneck (NeurIPS 2026 · similarity 0.91)
- Rethinking Optimal Verification Granularity for Compute-Efficient Test-Time Scaling (NeurIPS 2025 · similarity 0.90)
- What If We Allocate Test-Time Compute Adaptively? (ICML 2026 · similarity 0.90)
- Scaling Test-Time Compute Without Verification or RL is Suboptimal (ICML 2025 · similarity 0.90)
- V1: Unifying Generation and Self-Verification for Parallel Reasoners (ICML 2026 · similarity 0.89)
- Every Rollout Counts: Optimal Resource Allocation for Efficient Test-Time Scaling (NeurIPS 2025 · similarity 0.89)
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