arXiv AI

MGE-PO: Entropy-Aware Credit Assignment for Mathematical Reasoning

MGE-PO introduces an entropy-aware credit assignment framework for mathematical reasoning, using a four-quadrant advantage shaping that blends verified correctness with rollout generation entropy. The method assigns larger bonuses to low-entropy successful responses and larger penalties to high-entropy failures, guided by an online entropy-based question curriculum. Experiments on Qwen3-8B-Base and Qwen2.5-7B-Base show significant macro average and pass rate improvements across multiple benchmarks.

arXiv AI
Oct 1

Advancing Entropy-Level Credit Assignment in RLVR via Proximal Entropy Policy Optimization

The paper introduces Proximal Entropy Policy Optimization (PEPO), a method that assigns token‑level advantages in reinforcement learning for language models based on a local measure of entropy called proximal entropy. Unlike prior approaches that use global token entropy, PEPO evaluates importance relative to neighboring tokens, making it invariant to prompt difficulty and positional effects. Experiments on Qwen3 and Llama‑3.2 models show PEPO outperforms GRPO and other entropy‑based baselines in mathematical reasoning tasks.

By Yun Kim, Nojun Kwak
arXiv Machine Learning
Oct 19

Grounded Credit Assignment in Reinforcement Learning for Multi-Turn Search Agents

The paper introduces Grounded Credit Assignment (GCA) for reinforcement learning in multi‑turn search agents. GCA separates credit for evidence retrieval and answer correctness, correcting the bias in GRPO that favors evidence‑retrieving rollouts only proportionally to accuracy gains. Applying GCA to Search‑R1 boosts average EM by 5.7–6.3 points and increases the proportion of evidence‑supported correct answers from 76.9% to 93.4%.

By Qirui Liu, Hao Chen, Yi Wen, Weijie Shi, Yao Zhao, Xianhe Chen, Hao Zhao, Xing Tang, Weihong Luo, Yuyu Luo
arXiv AI
Sep 24

When and Where to Trust the Teacher: Unifying On-Policy Distillation and GRPO through Entropy-Calibrated Credit Assignment

The paper introduces UECR-GRPO, a method that unifies on‑policy distillation and verifier‑based reinforcement learning for mathematical reasoning. It combines verifier rewards and teacher‑derived log‑ratios into a single KL‑regularized objective (Path‑Utility Unification) and then redistributes credit at the token level using entropy‑calibrated redistribution, preserving total task credit. Experiments on five benchmarks show that UECR‑GRPO improves average accuracy by up to 0.89 percentage points over the best baseline for both Qwen3‑1.7B and Qwen3‑4B students.

By Jie Zhang, Jingxiao Yang, Zhehao Huang, Yuhang Liu, Xiaolin Huang
arXiv AI
Sep 15

HISPO: Hierarchical Importance-Sampling Policy Optimization with Entropy-Derived Segments

HISPO introduces a segment‑level policy‑optimization technique for reinforcement learning with verifiable rewards, creating entropy‑derived contiguous segments during rollout and applying clipped importance‑sampling correction at this granularity. It bridges the gap between token‑level and sequence‑level corrections, offering a middle‑ground approach for credit assignment in long‑form mathematical reasoning. Evaluated on Qwen3‑1.7B‑Base across six benchmarks, HISPO consistently outperforms or matches the strongest baselines in Pass@8 and Acc@8 metrics, notably improving AIME25 scores over GRPO and GSPO.

By Quoc-Vinh Lai-Dang, Hyo-Sang Shin
arXiv AI
Oct 15

Selective Successor Eligibility Traces for RLVR

The paper introduces Selective Successor Eligibility Traces (S-trace), a critic‑free eligibility trace method designed to improve temporal credit assignment in Reinforcement Learning with Verifiable Rewards (RLVR). S-trace reweights successor importance to recover downstream credit signals under PPO-style clipping and selectively propagates them to historical tokens using entropy-based token selection. Experiments on Qwen3 models show that S-trace yields significant absolute gains in average pass@16 over GRPO and trace-style GRPO, while also producing shorter responses.

By Chaoli Mou, Xinning Chen, Zhan Zhuang, Qinghe Zheng, Deyuan Kong, Yu Zhang