arXiv AI

GAC: Noise-Aware Adaptive Mixing for Hybrid SFT-RL Post-Training

The paper introduces GAC, a noise‑aware adaptive mixing controller that dynamically balances supervised fine‑tuning (SFT) and reinforcement learning (RL) gradients during hybrid post‑training of large language models. By deriving a closed‑form mixing weight that minimizes an MSE upper bound on the mixed gradient, GAC incorporates EMA smoothing, a schedule prior, and capped updates, all estimated online from training tensors. Experiments show that GAC outperforms rule‑based controllers, improving performance on diverse benchmarks by up to 3.8 percentage points, reducing KL‑drift by 28%, and cutting large mixing‑weight changes by over 70% with negligible overhead, with gains scaling from 1.5 B to 14 B parameters.

arXiv Machine Learning
Aug 4

AOS: Adaptive Optimizer Switching via Training-State Signals for Faster Convergence and Better Generalization

arXiv:2608. 01997v1 Announce Type: new Abstract: Single-optimizer training is a poor fit for the distinct phases of deep network optimization: adaptive methods handle noisy early gradients well but overshoot flat minima, while SGD with momentum generalizes better in the late phase but converges slowly early on.

By Alok Kumar Pandey, Umang Chaturvedi, Aatish Rana, Gopi Krishna Nedanuri
arXiv Machine Learning
Oct 8

COPC: Coupled Off-Policy Correction for Asynchronous LLM Reinforcement Learning

The paper introduces COPC, a Coupled Off-Policy Correction method for asynchronous reinforcement learning of large language models. COPC coordinates policy-side and advantage-side corrections by combining token-level ratio masking with two-sided clipped-ratio weighting of TD residuals, addressing both policy mismatch and advantage staleness. Experiments show COPC outperforms existing asynchronous baselines on tool-integrated mathematical reasoning and search tasks, while maintaining training stability and minimal overhead.

By Zicheng Hu, Zhijian Zhou, Xuan Zhang, Yuchen Liu, Cheng Chen, Yuan Li, Qi Gu, Yan Feng, Hongyan Hao, Chao Qu
arXiv AI
Sep 2

WHALE: A Simple Recipe for Joint Harness-Weight Optimization

The paper introduces WHALE, a method that alternates between updating a language model’s weights and searching for a better harness (the code that manages context and control flow). By iteratively fine‑tuning the model under the current harness and then optimizing the harness under the updated model, WHALE improves performance across search QA, math reasoning, and chess puzzles, outperforming weight‑only, harness‑only, and Fast‑Slow Training by 4.15–24.38 percentage points in mean@8 accuracy. The approach uses either fixed phase lengths or an adaptive patience rule to decide when to switch phases, and the authors provide code on GitHub.

By Haechan Kim, Yoonho Lee, Gisang Lee, Chelsea Finn, Kangwook Lee
arXiv Machine Learning
Sep 16

GrowMTP: Can RL Grow Its Own Draft Head?

GrowMTP is a method that trains a draft head entirely within the reinforcement learning (RL) loop, using supervision from the RL verification step and a rollout distribution that is narrower than pretraining. By detaching draft‑head updates from the policy backbone, it enables online training of the draft head from scratch. Experiments on Qwen3‑4B, MiMo‑7B‑SFT, and Qwen3.5‑4B‑Base show rollout speedups ranging from 1.36× to 2.13× and overall end‑to‑end speedups from 1.20× to 1.60×, making it a modular acceleration component for RL frameworks lacking pretrained draft heads.

By Minghua He, Lingzhe Zhang, Yuan Liu, Xiao Zhou, Aiwei Liu
arXiv AI
Sep 17

EfficientTDMPC: Improved MPC Objectives for Sample-Efficient Continuous Control

EfficientTDMPC is a sample‑efficient, model‑based reinforcement learning method for continuous control that builds on the TD‑MPC family. It reduces estimation error by using an ensemble of dynamics models and averaging return estimates across models and rollout depths, and it can penalize uncertainty in the planner objective. Practical improvements such as fresher buffer data and reduced compute enable the algorithm to benefit from a higher update‑to‑data ratio, achieving state‑of‑the‑art sample efficiency on HumanoidBench‑Hard and DMC hard while matching state‑of‑the‑art on DMC easy.

By Thomas Evers, Cristian Meo, Wendelin Bohmer, Justin Dauwels, Yaniv Oren
arXiv Machine Learning
Sep 2

Accelerating Reinforcement Learning via MPC Solver-Gradient Guidance for Weights-varying MPC

The paper introduces Solver-Gradient Guided Reinforcement Learning (SG‑RL), a method that augments standard RL with bounded gradients from a differentiable MPC solver to adapt cost‑function weights online. SG‑RL integrates solver‑gradient guidance into PPO through actor‑update scaling, policy loss, advantage estimation, and value‑function learning, achieving comparable or superior closed‑loop performance while requiring up to 70.6% fewer samples. Experiments on two autonomous racing platforms with intentional model mismatch demonstrate that SG‑RL outperforms both RL and gradient‑based policy learning baselines and generalizes zero‑shot to unseen environments.

By Baha Zarrouki, Arslan Thobani, Jasper Hoffmann, Mattia Piccinini, Rudolf Reiter, Felix Jahncke, S\'ebastien Gros, Davide Scaramuzza, Johannes Betz