FastFLUX: Pruning FLUX with Block-wise Replacement and Sandwich Training

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Main Authors: Cai, Fuhan, Guo, Yong, Li, Jie, Li, Wenbo, Chen, Jian, Fang, Xiangzhong
Format: Preprint
Published: 2025
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author Cai, Fuhan
Guo, Yong
Li, Jie
Li, Wenbo
Chen, Jian
Fang, Xiangzhong
author_facet Cai, Fuhan
Guo, Yong
Li, Jie
Li, Wenbo
Chen, Jian
Fang, Xiangzhong
contents Recent advancements in text-to-image (T2I) generation have led to the emergence of highly expressive models such as diffusion transformers (DiTs), exemplified by FLUX. However, their massive parameter sizes lead to slow inference, high memory usage, and poor deployability. Existing acceleration methods (e.g., single-step distillation and attention pruning) often suffer from significant performance degradation and incur substantial training costs. To address these limitations, we propose FastFLUX, an architecture-level pruning framework designed to enhance the inference efficiency of FLUX. At its core is the Block-wise Replacement with Linear Layers (BRLL) method, which replaces structurally complex residual branches in ResBlocks with lightweight linear layers while preserving the original shortcut connections for stability. Furthermore, we introduce Sandwich Training (ST), a localized fine-tuning strategy that leverages LoRA to supervise neighboring blocks, mitigating performance drops caused by structural replacement. Experiments show that our FastFLUX maintains high image quality under both qualitative and quantitative evaluations, while significantly improving inference speed, even with 20\% of the hierarchy pruned. Our code will be available soon.
format Preprint
id arxiv_https___arxiv_org_abs_2506_10035
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle FastFLUX: Pruning FLUX with Block-wise Replacement and Sandwich Training
Cai, Fuhan
Guo, Yong
Li, Jie
Li, Wenbo
Chen, Jian
Fang, Xiangzhong
Graphics
Artificial Intelligence
Recent advancements in text-to-image (T2I) generation have led to the emergence of highly expressive models such as diffusion transformers (DiTs), exemplified by FLUX. However, their massive parameter sizes lead to slow inference, high memory usage, and poor deployability. Existing acceleration methods (e.g., single-step distillation and attention pruning) often suffer from significant performance degradation and incur substantial training costs. To address these limitations, we propose FastFLUX, an architecture-level pruning framework designed to enhance the inference efficiency of FLUX. At its core is the Block-wise Replacement with Linear Layers (BRLL) method, which replaces structurally complex residual branches in ResBlocks with lightweight linear layers while preserving the original shortcut connections for stability. Furthermore, we introduce Sandwich Training (ST), a localized fine-tuning strategy that leverages LoRA to supervise neighboring blocks, mitigating performance drops caused by structural replacement. Experiments show that our FastFLUX maintains high image quality under both qualitative and quantitative evaluations, while significantly improving inference speed, even with 20\% of the hierarchy pruned. Our code will be available soon.
title FastFLUX: Pruning FLUX with Block-wise Replacement and Sandwich Training
topic Graphics
Artificial Intelligence
url https://arxiv.org/abs/2506.10035