Evolutionary Token-Level Prompt Optimization for Diffusion Models

Fuente: arXiv
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Main Authors: Neto, Domício Pereira, Correia, João, Machado, Penousal
Format: Preprint
Published: 2026
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author Neto, Domício Pereira
Correia, João
Machado, Penousal
author_facet Neto, Domício Pereira
Correia, João
Machado, Penousal
contents Text-to-image diffusion models exhibit strong generative performance but remain highly sensitive to prompt formulation, often requiring extensive manual trial and error to obtain satisfactory results. This motivates the development of automated, model-agnostic prompt optimization methods that can systematically explore the conditioning space beyond conventional text rewriting. This work investigates the use of a Genetic Algorithm (GA) for prompt optimization by directly evolving the token vectors employed by CLIP-based diffusion models. The GA optimizes a fitness function that combines aesthetic quality, measured by the LAION Aesthetic Predictor V2, with prompt-image alignment, assessed via CLIPScore. Experiments on 36 prompts from the Parti Prompts (P2) dataset show that the proposed approach outperforms the baseline methods, including Promptist and random search, achieving up to a 23.93% improvement in fitness. Overall, the method is adaptable to image generation models with tokenized text encoders and provides a modular framework for future extensions, the limitations and prospects of which are discussed.
format Preprint
id arxiv_https___arxiv_org_abs_2604_09861
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Evolutionary Token-Level Prompt Optimization for Diffusion Models
Neto, Domício Pereira
Correia, João
Machado, Penousal
Artificial Intelligence
Neural and Evolutionary Computing
Text-to-image diffusion models exhibit strong generative performance but remain highly sensitive to prompt formulation, often requiring extensive manual trial and error to obtain satisfactory results. This motivates the development of automated, model-agnostic prompt optimization methods that can systematically explore the conditioning space beyond conventional text rewriting. This work investigates the use of a Genetic Algorithm (GA) for prompt optimization by directly evolving the token vectors employed by CLIP-based diffusion models. The GA optimizes a fitness function that combines aesthetic quality, measured by the LAION Aesthetic Predictor V2, with prompt-image alignment, assessed via CLIPScore. Experiments on 36 prompts from the Parti Prompts (P2) dataset show that the proposed approach outperforms the baseline methods, including Promptist and random search, achieving up to a 23.93% improvement in fitness. Overall, the method is adaptable to image generation models with tokenized text encoders and provides a modular framework for future extensions, the limitations and prospects of which are discussed.
title Evolutionary Token-Level Prompt Optimization for Diffusion Models
topic Artificial Intelligence
Neural and Evolutionary Computing
url https://arxiv.org/abs/2604.09861