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LongChart VQA: A Comprehensive Benchmark for MLLMs with Complex Multi-Chart Reasoning

Aug 2026 · 0 citations · 35 references
Computer Science

TL;DR

This work evaluates 10 state-of-the-art MLLMs and examines three factors that influence performance: reasoning patterns, auxiliary tools, and robustness to image perturbations, showing that MLLM accuracy decreases and varies substantially as computational complexity increases.

Abstract

Multimodal large language models (MLLMs) are rapidly evolving with expanded context windows and stronger reasoning capabilities, enabling multi-chart understanding and multi-step inference. These abilities are increasingly important as MLLMs are adopted in complex agentic tasks. However, existing benchmarks largely emphasize single-chart perception, while simple chart-to-chart connections are insufficient to evaluate these capabilities. To capture multi-chart complexity while ensuring consistency and validity, we design a synthesis pipeline supported by latent graphs. Building on this pipeline, we introduce LongChart, a benchmark whose VQA sets contain an average of 6.5 images and 31.2 questions. We evaluate 10 state-of-the-art MLLMs and examine three factors that influence performance: reasoning patterns, auxiliary tools, and robustness to image perturbations. Our results show that MLLM accuracy decreases and varies substantially as computational complexity increases, highlighting directions for future research in multi-chart reasoning.

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