MMR1: Enhancing Multimodal Reasoning with Variance-Aware Sampling and
  Open Resources
Authors: name: Sicong Leng; name: Jing Wang; name: Jiaxi Li; name: Hao Zhang; name: Zhiqiang Hu; name: Boqiang Zhang; name: Yuming Jiang; name: Hang Zhang; name: Xin Li; name: Lidong Bing; name: Deli Zhao; name: Wei Lu; name: Yu Rong; name: Aixin Sun; name: Shijian Lu
Published: 2025-09-25 14:58:29

Abstract: Large multimodal reasoning models have achieved rapid progress, but their
advancement is constrained by two major limitations: the absence of open,
large-scale, high-quality long chain-of-thought (CoT) data, and the instability
of reinforcement learning (RL) algorithms in post-training. Group Relative
Policy Optimization (GRPO), the standard framework for RL fine-tuning, is prone
to gradient vanishing when reward variance is low, which weakens optimization
signals and impairs convergence. This work makes three contributions: (1) We
propose Variance-Aware Sampling (VAS), a data selection strategy guided by
Variance Promotion Score (VPS) that combines outcome variance and trajectory
diversity to promote reward variance and stabilize policy optimization. (2) We
release large-scale, carefully curated resources containing ~1.6M long CoT
cold-start data and ~15k RL QA pairs, designed to ensure quality, difficulty,
and diversity, along with a fully reproducible end-to-end training codebase.
(3) We open-source a family of multimodal reasoning models in multiple scales,
establishing standardized baselines for the community. Experiments across
mathematical reasoning benchmarks demonstrate the effectiveness of both the
curated data and the proposed VAS. Comprehensive ablation studies and analyses
provide further insight into the contributions of each component. In addition,
we theoretically establish that reward variance lower-bounds the expected
policy gradient magnitude, with VAS serving as a practical mechanism to realize
this guarantee. Our code, data, and checkpoints are available at
https://github.com/LengSicong/MMR1.