135 research outputs found
Ridge Regression, Hubness, and Zero-Shot Learning
This paper discusses the effect of hubness in zero-shot learning, when ridge
regression is used to find a mapping between the example space to the label
space. Contrary to the existing approach, which attempts to find a mapping from
the example space to the label space, we show that mapping labels into the
example space is desirable to suppress the emergence of hubs in the subsequent
nearest neighbor search step. Assuming a simple data model, we prove that the
proposed approach indeed reduces hubness. This was verified empirically on the
tasks of bilingual lexicon extraction and image labeling: hubness was reduced
with both of these tasks and the accuracy was improved accordingly.Comment: To be presented at ECML/PKDD 201
Generalized Zero-Shot Learning via Synthesized Examples
We present a generative framework for generalized zero-shot learning where
the training and test classes are not necessarily disjoint. Built upon a
variational autoencoder based architecture, consisting of a probabilistic
encoder and a probabilistic conditional decoder, our model can generate novel
exemplars from seen/unseen classes, given their respective class attributes.
These exemplars can subsequently be used to train any off-the-shelf
classification model. One of the key aspects of our encoder-decoder
architecture is a feedback-driven mechanism in which a discriminator (a
multivariate regressor) learns to map the generated exemplars to the
corresponding class attribute vectors, leading to an improved generator. Our
model's ability to generate and leverage examples from unseen classes to train
the classification model naturally helps to mitigate the bias towards
predicting seen classes in generalized zero-shot learning settings. Through a
comprehensive set of experiments, we show that our model outperforms several
state-of-the-art methods, on several benchmark datasets, for both standard as
well as generalized zero-shot learning.Comment: Accepted in CVPR'1
HAL: Improved Text-Image Matching by Mitigating Visual Semantic Hubs
The hubness problem widely exists in high-dimensional embedding space and is
a fundamental source of error for cross-modal matching tasks. In this work, we
study the emergence of hubs in Visual Semantic Embeddings (VSE) with
application to text-image matching. We analyze the pros and cons of two widely
adopted optimization objectives for training VSE and propose a novel
hubness-aware loss function (HAL) that addresses previous methods' defects.
Unlike (Faghri et al.2018) which simply takes the hardest sample within a
mini-batch, HAL takes all samples into account, using both local and global
statistics to scale up the weights of "hubs". We experiment our method with
various configurations of model architectures and datasets. The method exhibits
exceptionally good robustness and brings consistent improvement on the task of
text-image matching across all settings. Specifically, under the same model
architectures as (Faghri et al. 2018) and (Lee at al. 2018), by switching only
the learning objective, we report a maximum R@1improvement of 7.4% on MS-COCO
and 8.3% on Flickr30k.Comment: AAAI-20 (to appear
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