MileBench: Benchmarking MLLMs in Long Context

TL;DR

MileBench is a new benchmark designed to evaluate Multimodal Large Language Models' ability to handle long contexts and multiple images across various tasks, revealing current limitations especially in open-source models.

Contribution

This paper introduces MileBench, the first comprehensive benchmark for testing MLLMs on long-context, multi-image tasks, filling a gap in existing evaluation methods.

Findings

GPT-4o outperforms other models in long-context tasks.

Most open-source MLLMs struggle with long contexts, especially with multiple images.

Performance gaps increase as the number of images grows.

Abstract

Despite the advancements and impressive performance of Multimodal Large Language Models (MLLMs) on benchmarks, their effectiveness in real-world, long-context, and multi-image tasks is unclear due to the benchmarks' limited scope. Existing benchmarks often focus on single-image and short-text samples, and when assessing multi-image tasks, they either limit the image count or focus on specific task (e.g time-series captioning), potentially obscuring the performance challenges of MLLMs. To address these limitations, we introduce MileBench, a pioneering benchmark designed to test the MultImodal Long-contExt capabilities of MLLMs. This benchmark comprises not only multimodal long contexts, but also multiple tasks requiring both comprehension and generation. We establish two distinct evaluation sets, diagnostic and realistic, to systematically assess MLLMs' long-context adaptation capacity and their ability to complete tasks in long-context scenarios. Our experimental results, obtained from testing 22 models, revealed that while the closed-source GPT-4o outperforms others, most open-source MLLMs struggle in long-context situations. Interestingly, the performance gap tends to widen with an increase in the number of images. We strongly encourage an intensification of research efforts towards enhancing MLLMs' long-context capabilities, especially in scenarios involving multiple images.