Hydra: Multi-head Low-rank Adaptation for Parameter Efficient Fine-tuning

The recent surge in large-scale foundation models has spurred the development of efficient methods for adapting these models to various downstream tasks. Low-rank adaptation methods, such as LoRA, have gained significant attention due to their outstanding parameter efficiency and no additional inference latency. This paper investigates a more general form of adapter module based on the analysis that parallel and sequential adaptation branches learn novel and general features during fine-tuning, respectively. The proposed method, named Hydra, due to its multi-head computational branches, combines parallel and sequential branch to integrate capabilities, which is more expressive than existing single branch methods and enables the exploration of a broader range of optimal points in the fine-tuning process. In addition, the proposed adaptation method explicitly leverages the pre-trained weights by performing a linear combination of the pre-trained features. It allows the learned features to have better generalization performance across diverse downstream tasks. Furthermore, we perform a comprehensive analysis of the characteristics of each adaptation branch with empirical evidence. Through an extensive range of experiments, encompassing comparisons and ablation studies, we substantiate the efficiency and demonstrate the superior performance of Hydra. This comprehensive evaluation underscores the potential impact and effectiveness of Hydra in a variety of applications. Our code is available on \url{https://github.com/extremebird/Hydra}

Explaining Visual Biases as Words by Generating Captions

We aim to diagnose the potential biases in image classifiers. To this end, prior works manually labeled biased attributes or visualized biased features, which need high annotation costs or are often ambiguous to interpret. Instead, we leverage two types (generative and discriminative) of pre-trained vision-language models to describe the visual bias as a word. Specifically, we propose bias-to-text (B2T), which generates captions of the mispredicted images using a pre-trained captioning model to extract the common keywords that may describe visual biases. Then, we categorize the bias type as spurious correlation or majority bias by checking if it is specific or agnostic to the class, based on the similarity of class-wise mispredicted images and the keyword upon a pre-trained vision-language joint embedding space, e.g., CLIP. We demonstrate that the proposed simple and intuitive scheme can recover well-known gender and background biases, and discover novel ones in real-world datasets. Moreover, we utilize B2T to compare the classifiers using different architectures or training methods. Finally, we show that one can obtain debiased classifiers using the B2T bias keywords and CLIP, in both zero-shot and full-shot manners, without using any human annotation on the bias.

ORA3D: Overlap Region Aware Multi-view 3D Object Detection

In multi-view 3D object detection tasks, disparity supervision over overlapping image regions substantially improves the overall detection performance. However, current multi-view 3D object detection methods often fail to detect objects in the overlap region properly, and the network's understanding of the scene is often limited to that of a monocular detection network. To mitigate this issue, we advocate for applying the traditional stereo disparity estimation method to obtain reliable disparity information for the overlap region. Given the disparity estimates as a supervision, we propose to regularize the network to fully utilize the geometric potential of binocular images, and improve the overall detection accuracy. Moreover, we propose to use an adversarial overlap region discriminator, which is trained to minimize the representational gap between non-overlap regions and overlapping regions where objects are often largely occluded or suffer from deformation due to camera distortion, causing a domain shift. We demonstrate the effectiveness of the proposed method with the large-scale multi-view 3D object detection benchmark, called nuScenes. Our experiment shows that our proposed method outperforms the current state-of-the-art methods.