arXiv AI

T-Router: Learning Thalamic Routing for Reasoning with Parameter-Efficient Reinforcement Learning

The paper introduces T‑Router, a parameter‑efficient reinforcement learning framework that learns thalamic routing to improve reasoning with a pretrained model. T‑Router focuses adaptation on reusing completed computations via a compressed, addressable bank and a depth‑recurrent controller, allocating only 0.466% of the backbone parameters while achieving higher MathAvg scores on GSM8K and improving AIME accuracy. The study demonstrates that controlled computation reuse can outperform full‑parameter and LoRA approaches in reasoning tasks.

arXiv Machine Learning
3d ago

Route-and-Generate: KL-Regularized Router Improvement for Reasoning Routing in LLMs

Route-and-Generate (Rouge) is a hierarchical training framework that lets large language models decide how much reasoning to apply to each input. It separates reasoning effort from answer generation by using a routing policy that distributes a fixed sampling budget across different reasoning formats, while the base model is trained with GRPO and per-sample rewards. The method employs a rank‑based reward favoring shorter correct solutions and updates the router through a closed‑form KL‑regularized policy improvement, leading to more concise answers on easy tasks and longer reasoning on harder ones, thereby improving accuracy‑efficiency trade‑offs on multiple reasoning benchmarks.

By Tien-Phat Nguyen, Truong Nguyen, Thanh-Thien Le, Hoang Phan, Thien Huu Nguyen, Linh Ngo Van, Trung Le
arXiv AI
Sep 25

CounterRoute: Self-Routed Reasoning via Hierarchical Counterfactual Credit Assignment

CounterRoute is an online reinforcement‑learning framework that jointly learns how to route a language model’s reasoning between a ‘think’ and a ‘direct answer’ mode, using a single shared policy derived from a dual‑mode checkpoint. It employs counterfactual rollouts to credit routing decisions and a curriculum that starts with forced dual‑mode rollouts before shifting to self‑routed updates, achieving better accuracy‑efficiency trade‑offs across nine benchmarks. The method reduces generated tokens by up to 51% on Qwen3‑8B while improving macro‑average accuracy, and its routing strategy generalizes to unseen coding, science, and commonsense tasks.

By Ruochen Jiao, Besnik Fetahu, Zhenyu Shi, Priyanka Nigam
arXiv Machine Learning
Aug 14

RoutePack: Expert Placement and Attention-Aware Data Packing for MoE Reinforcement Learning

arXiv:2608. 12146v1 Announce Type: cross Abstract: Training Mixture-of-Experts (MoE) models for reinforcement learning (RL) couples two load-balancing problems: sequence composition determines dense attention work in each data-parallel microbatch, while token routing determines sparse expert work on expert-parallel ranks.

By Yibo Shen, Xudong Han, Xiaowei Zhu, Gen Li, Zhenxuan Pan
arXiv AI
Sep 18

When2Think: Learning Difficulty-Aware Length Control for Efficient Hybrid Reasoning Models

When2Think introduces a post‑training framework that dynamically allocates reasoning depth in Large Reasoning Models based on instance difficulty. The method uses Instance‑level Difficulty‑Aware Control (IDAC) to shape rewards with pre‑computed accuracy and token usage statistics, enabling stable, critic‑free optimization without learned reward models. Experiments on mathematical benchmarks show that When2Think improves accuracy‑efficiency trade‑offs, achieving higher Pass@3 scores while reducing token usage compared to baseline models.

By Jaejun Shim, HyunJin Kim, Young Jin Kim, JinYeong Bak