Building Ensemble of Deep Networks: Convolutional Networks and Transformers

This paper presents a study on an automated system for image classification, which is based on the fusion of various deep learning methods. The study explores how to create an ensemble of different Convolutional Neural Network (CNN) models and transformer topologies that are fine-tuned on several datasets to leverage their diversity. The research question addressed in this work is whether different optimization algorithms can help in developing robust and efficient machine learning systems to be used in different domains for classification purposes. To do that, we introduce novel Adam variants. We employed these new approaches, coupled with several CNN topologies, for building an ensemble of classifiers that outperforms both other Adam-based methods and stochastic gradient descent. Additionally, the study combines the ensemble of CNNs with an ensemble of transformers based on different topologies, such as Deit, Vit, Swin, and Coat. To the best of our knowledge, this is the first work in which an in-depth study of a set of transformers and convolutional neural networks in a large set of small/medium-sized images is carried out. The experiments performed on several datasets demonstrate that the combination of such different models results in a substantial performance improvement in all tested problems. All resources are available at https://github.com/LorisNanni.