MoDoMoDo: Multi-Domain Data Mixtures for Multimodal LLM Reinforcement
  Learning
Authors: name: Yiqing Liang, name: Jielin Qiu, name: Wenhao Ding, name: Zuxin Liu, name: James Tompkin, name: Mengdi Xu, name: Mengzhou Xia, name: Zhengzhong Tu, name: Laixi Shi, name: Jiacheng Zhu

Reinforcement Learning with Verifiable Rewards (RLVR) has recently emerged as
a powerful paradigm for post-training large language models (LLMs), achieving
state-of-the-art performance on tasks with structured, verifiable answers.
Applying RLVR to Multimodal LLMs (MLLMs) presents significant opportunities but
is complicated by the broader, heterogeneous nature of vision-language tasks
that demand nuanced visual, logical, and spatial capabilities. As such,
training MLLMs using RLVR on multiple datasets could be beneficial but creates
challenges with conflicting objectives from interaction among diverse datasets,
highlighting the need for optimal dataset mixture strategies to improve
generalization and reasoning. We introduce a systematic post-training framework
for Multimodal LLM RLVR, featuring a rigorous data mixture problem formulation
and benchmark implementation. Specifically, (1) We developed a multimodal RLVR
framework for multi-dataset post-training by curating a dataset that contains
different verifiable vision-language problems and enabling multi-domain online
RL learning with different verifiable rewards; (2) We proposed a data mixture
strategy that learns to predict the RL fine-tuning outcome from the data
mixture distribution, and consequently optimizes the best mixture.
Comprehensive experiments showcase that multi-domain RLVR training, when
combined with mixture prediction strategies, can significantly boost MLLM
general reasoning capacities. Our best mixture improves the post-trained
model's accuracy on out-of-distribution benchmarks by an average of 5.24%
compared to the same model post-trained with uniform data mixture, and by a
total of 20.74% compared to the pre-finetuning baseline.