Cornstarch: Distributed Multimodal Training Must Be Multimodality-Aware

Abstract: Multimodal LLMs (MLLMs) extend the capabilities of LLMs by combining heterogeneous model architectures to handle diverse modalities like images and audio. However, this inherent heterogeneity in MLLM model structure and data types makes makeshift extensions to existing LLM training frameworks unsuitable for efficient MLLM training. In this paper, we present Cornstarch, the first general-purpose distributed MLLM training framework. Cornstarch facilitates modular MLLM construction, enables composable parallelization of constituent models, and introduces MLLM-specific optimizations to pipeline and context parallelism for efficient distributed MLLM training. Our evaluation shows that Cornstarch outperforms state-of-the-art solutions by up to $1.57\times$ in terms of training throughput. Cornstarch is an open-source project available at https://github.com/cornstarch-org/Cornstarch.