Reinforcement Learning with Verifiable Rewards (RLVR) has become the leading paradigm for enhancing reasoning in Large Language Models (LLMs). However, standard RLVR algorithms suffer from a well-documented pathology: while they improve Pass@1 accuracy through sharpened sampling, they simultaneously narrow the model's reasoning boundary and reduce generation diversity. We identify a root cause that existing methods overlook: the uniform penalization of errors. Current approaches -- whether data-filtering methods that select prompts by difficulty, or advantage normalization schemes -- treat all incorrect rollouts within a group identically. We show that this uniformity allows overconfident errors (incorrect reasoning paths that the RL process has spuriously reinforced) to persist and monopolize probability mass, ultimately suppressing valid exploratory trajectories. To address this, we propose the Asymmetric Confidence-aware Error Penalty (ACE). ACE introduces a per-rollout confidence shift metric, c_i = log(pi_theta(y_i|x) / pi_ref(y_i|x)), to dynamically modulate negative advantages. Theoretically, we demonstrate that ACE's gradient can be decomposed into the gradient of a selective regularizer restricted to overconfident errors, plus a well-characterized residual that partially moderates the regularizer's strength. We conduct extensive experiments fine-tuning Qwen2.5-Math-7B, Qwen3-8B-Base, and Llama-3.1-8B-Instruct on the DAPO-Math-17K dataset using GRPO and DAPO within the VERL framework. Evaluated on MATH-500 and AIME 2025, ACE composes seamlessly with existing methods and consistently improves the full Pass@k spectrum across all three model families and benchmarks.
Figures & tables
Figure 1: ACE Method Overview. Top: Incorrect rollouts fall into three regimes based on the confidence shift ci=log(πθ(yi∣x)/πref(yi∣x)) . Bottom-left: Standard GRPO assigns a uniform penalty ∣A^−∣ to all errors regardless of regime. Bottom-right: ACE modulates the penalty via Softplus(ci) , strongly penalizing overconfident errors while leaving self-correcting errors nearly untouched.
Model
@1
@2
@4
@8
@16
@32
Qwen2.5-Math-7B
63.0
76.3
83.2
88.1
91.2
93.5
Qwen2.5-Math-7B + GRPO
73.4 ± 0.8
79.5 ± 0.7
83.2 ± 0.7
86.2 ± 0.5
89.7 ± 0.5
91.3 ± 0.5
Qwen2.5-Math-7B + DAPO
74.5 ± 1.0
80.8 ± 0.9
84.8 ± 0.8
89.5 ± 0.7
93.0 ± 0.7
94.6 ± 0.6
Qwen2.5-Math-7B + ACE-GRPO
74.2 ± 0.7
80.9 ± 0.7
84.5 ± 0.6
88.9 ± 0.5
92.6 ± 0.5
94.3 ± 0.4
Qwen2.5-Math-7B + ACE-DAPO
75.1 ± 0.8
82.4 ± 0.8
86.2 ± 0.6
91.2 ± 0.5
94.7 ± 0.5
96.1 ± 0.5
Qwen3-8B-Base
60.2
72.5
78.8
83.9
87.2
90.6
Table 1: Pass@ k (%) on MATH-500. We report mean ± 95% confidence interval over 5 independent training runs. Bold = best within each model group; underline = second best.
Model
1
2
4
8
16
32
Qwen2.5-Math-7B
6.3
9.9
13.8
17.5
21.9
26.7
Qwen2.5-Math-7B + GRPO
10.5
14.9
19.7
23.9
28.6
33.7
Qwen2.5-Math-7B + DAPO
11.5
16.7
22.5
27.5
31.8
37.1
Qwen2.5-Math-7B + ACE-GRPO
11.2
16.0
21.2
26.1
30.6
36.4
Qwen2.5-Math-7B + ACE-DAPO
11.7
17.4
23.8
28.5
33.1
38.6
Qwen3-8B-Base
5.1
9.2
11.6
14.2
17.0
19.6
Table 2: Pass@ k (%) on AIME 2025. AIME 2025 contains 30 problems; we report point estimates as confidence intervals are dominated by test-set size rather than training variance. Bold = best within each model group; underline = second best.
Figure 2: Performance Comparison across Benchmarks. Pass@ k curves for all five methods on MATH-500 (left column) and AIME 2025 (right column) across three model families: Qwen2.5-Math-7B (top row), Qwen3-8B-Base (middle row), and Llama-3.1-8B-Instruct (bottom row). ACE-GRPO and ACE-DAPO consistently outperform their respective baselines (GRPO and DAPO) across all sampling budgets, model families, and benchmarks, with larger gains at higher k values. ACE-DAPO achieves the best overall performance, confirming that ACE’s rollout-level correction composes with DAPO’s token-level diversity preservation and generalizes across model families.
Figure 3: Overconfident Error Dynamics. Left: Overconfident error fraction (OEF) over training. Right: Mean overconfidence magnitude for ci>0 errors. ACE-GRPO effectively suppresses both metrics compared to standard GRPO.
Figure 4: Entropy Dynamics. Token-level entropy over the first 20 training steps. Left: On Qwen2.5-Math-7B, ACE-GRPO retains substantially more entropy than standard GRPO, which suffers rapid entropy collapse. Right: On Qwen3-8B-Base, ACE-GRPO maintains more stable entropy, demonstrating consistency across architectures. We report entropy dynamics for the two Qwen models only; Llama-3.1-8B-Instruct is excluded because its lower baseline accuracy makes the entropy signal less directly comparable (see § 5 for discussion).
Method
@1
@2
@4
@8
@16
@32
GRPO (baseline)
73.4
79.5
83.2
86.2
89.7
91.3
ACE-ReLU
73.2
80.3
83.9
87.6
91.2
93.1
ACE-Softplus (ours)
74.2
80.9
84.5
88.9
92.6
94.3
Table 3: Ablation: modulation function on MATH-500 (Qwen2.5-Math-7B, α=1.0 ).
Appendix figures & tables2 assets
Supplementary material from the paper’s appendix.
Appendix
α
Pass@1 (%)
Pass@32 (%)
0.0 (GRPO)
73.4
91.3
0.1
73.5
91.9
0.5
73.8
93.2
1.0 (default)
74.2
94.3
2.0
73.5
93.5
5.0
72.4
92.0
Appendix
Table 4: Sensitivity to α on MATH-500 (Qwen2.5-Math-7B). α=1.0 achieves optimal Pass@32 while preserving Pass@1.
Hyperparameter
Qwen2.5-Math-7B
Qwen3-8B-Base
Llama-3.1-8B-Instruct
Total epochs
10
10
10
Training batch size
2048
1024
1024
Mini-batch size
1024
1024
1024
Micro-batch size per GPU
16
16
16
Learning rate
1×10−5
5×10−7
1×10−6
Optimizer
AdamW
AdamW
AdamW
Appendix
Table 5: Training hyperparameters for ACE-GRPO experiments.