Prabhant Singh

Prabhant Singh, Joaquin Vanschoren

Neural Architecture Search (NAS) methods have been shown to outperform hand-designed models and help to democratize AI. However, NAS methods often start from scratch with each new task, making them computationally expensive and limiting their applicability. Transfer learning is a practical alternative with the rise of ever-larger pretrained models. However, it is also bound to the architecture of the pretrained model, which inhibits proper adaptation of the architecture to different tasks, leading to suboptimal (and excessively large) models. We address both challenges at once by introducing a novel and practical method to \textit{transfer supernets}, which parameterize both weight and architecture priors, and efficiently finetune both to new tasks. This enables supernet transfer learning as a replacement for traditional transfer learning that also finetunes model architectures to new tasks. Through extensive experiments across multiple image classification tasks, we demonstrate that supernet transfer learning does not only drastically speed up the discovery of optimal models (3 to 5 times faster on average), but will also find better models than running NAS from scratch. The added model flexibility also increases the robustness of transfer learning, yielding positive transfer to even very different target datasets, especially with multi-dataset pretraining.

Prabhant Singh, Pieter Gijsbers, Elif Ceren Gok Yildirim et al.

In this work, we present LOTUS (Learning to Learn with Optimal Transport for Unsupervised Scenarios), a simple yet effective method to perform model selection for multiple unsupervised machine learning(ML) tasks such as outlier detection and clustering. Our intuition behind this work is that a machine learning pipeline will perform well in a new dataset if it previously worked well on datasets with a similar underlying data distribution. We use Optimal Transport distances to find this similarity between unlabeled tabular datasets and recommend machine learning pipelines with one unified single method on two downstream unsupervised tasks: outlier detection and clustering. We present the effectiveness of our approach with experiments against strong baselines and show that LOTUS is a very promising first step toward model selection for multiple unsupervised ML tasks.

Prabhant Singh, Tobias Jacobs, Sebastien Nicolas et al.

In neural architecture search, the structure of the neural network to best model a given dataset is determined by an automated search process. Efficient Neural Architecture Search (ENAS), proposed by Pham et al. (2018), has recently received considerable attention due to its ability to find excellent architectures within a comparably short search time. In this work, which is motivated by the quest to further improve the learning speed of architecture search, we evaluate the learning progress of the controller which generates the architectures in ENAS. We measure the progress by comparing the architectures generated by it at different controller training epochs, where architectures are evaluated after having re-trained them from scratch. As a surprising result, we find that the learning curves are completely flat, i.e., there is no observable progress of the controller in terms of the performance of its generated architectures. This observation is consistent across the CIFAR-10 and CIFAR-100 datasets and two different search spaces. We conclude that the high quality of the models generated by ENAS is a result of the search space design rather than the controller training, and our results indicate that one-shot architecture design is an efficient alternative to architecture search by ENAS.