122,138 research outputs found
Representation Learning on Unstructured Data
Representation learning, which transfers real world data such as graphs, images and texts, into representations that can be effectively processed by machine learning algorithms, has became a new focus in machine learning community. Traditional machine learning algorithms usually focus on modeling hand-crafted feature representations manually extracted from the raw data and performance of the model highly depends on the quality of the data representation. However, feature engineering is laborious, hardly accurate, and less generalizable. Thus the weakness of many current learning algorithms is not how well they can model the data, but how good their input data representation are.In this thesis, we adopt learning algorithms both on representing and modeling the graph data in two different applications. In the first work, We first developed representation on nodes, and later apply a well-known VG kernel on this representation. In the second work, we show the power of representation captured by applying jointly optimization on the nodes representations and the model. The results of both work show significant improvement over traditional machine learning methods
Learning parametric dictionaries for graph signals
In sparse signal representation, the choice of a dictionary often involves a
tradeoff between two desirable properties -- the ability to adapt to specific
signal data and a fast implementation of the dictionary. To sparsely represent
signals residing on weighted graphs, an additional design challenge is to
incorporate the intrinsic geometric structure of the irregular data domain into
the atoms of the dictionary. In this work, we propose a parametric dictionary
learning algorithm to design data-adapted, structured dictionaries that
sparsely represent graph signals. In particular, we model graph signals as
combinations of overlapping local patterns. We impose the constraint that each
dictionary is a concatenation of subdictionaries, with each subdictionary being
a polynomial of the graph Laplacian matrix, representing a single pattern
translated to different areas of the graph. The learning algorithm adapts the
patterns to a training set of graph signals. Experimental results on both
synthetic and real datasets demonstrate that the dictionaries learned by the
proposed algorithm are competitive with and often better than unstructured
dictionaries learned by state-of-the-art numerical learning algorithms in terms
of sparse approximation of graph signals. In contrast to the unstructured
dictionaries, however, the dictionaries learned by the proposed algorithm
feature localized atoms and can be implemented in a computationally efficient
manner in signal processing tasks such as compression, denoising, and
classification
Multi-level 3D CNN for Learning Multi-scale Spatial Features
3D object recognition accuracy can be improved by learning the multi-scale
spatial features from 3D spatial geometric representations of objects such as
point clouds, 3D models, surfaces, and RGB-D data. Current deep learning
approaches learn such features either using structured data representations
(voxel grids and octrees) or from unstructured representations (graphs and
point clouds). Learning features from such structured representations is
limited by the restriction on resolution and tree depth while unstructured
representations creates a challenge due to non-uniformity among data samples.
In this paper, we propose an end-to-end multi-level learning approach on a
multi-level voxel grid to overcome these drawbacks. To demonstrate the utility
of the proposed multi-level learning, we use a multi-level voxel representation
of 3D objects to perform object recognition. The multi-level voxel
representation consists of a coarse voxel grid that contains volumetric
information of the 3D object. In addition, each voxel in the coarse grid that
contains a portion of the object boundary is subdivided into multiple
fine-level voxel grids. The performance of our multi-level learning algorithm
for object recognition is comparable to dense voxel representations while using
significantly lower memory.Comment: CVPR 2019 workshop on Deep Learning for Geometric Shape Understandin
Learning over Knowledge-Base Embeddings for Recommendation
State-of-the-art recommendation algorithms -- especially the collaborative
filtering (CF) based approaches with shallow or deep models -- usually work
with various unstructured information sources for recommendation, such as
textual reviews, visual images, and various implicit or explicit feedbacks.
Though structured knowledge bases were considered in content-based approaches,
they have been largely neglected recently due to the availability of vast
amount of data, and the learning power of many complex models.
However, structured knowledge bases exhibit unique advantages in personalized
recommendation systems. When the explicit knowledge about users and items is
considered for recommendation, the system could provide highly customized
recommendations based on users' historical behaviors. A great challenge for
using knowledge bases for recommendation is how to integrated large-scale
structured and unstructured data, while taking advantage of collaborative
filtering for highly accurate performance. Recent achievements on knowledge
base embedding sheds light on this problem, which makes it possible to learn
user and item representations while preserving the structure of their
relationship with external knowledge. In this work, we propose to reason over
knowledge base embeddings for personalized recommendation. Specifically, we
propose a knowledge base representation learning approach to embed
heterogeneous entities for recommendation. Experimental results on real-world
dataset verified the superior performance of our approach compared with
state-of-the-art baselines
Model Debiasing via Gradient-based Explanation on Representation
Machine learning systems produce biased results towards certain demographic
groups, known as the fairness problem. Recent approaches to tackle this problem
learn a latent code (i.e., representation) through disentangled representation
learning and then discard the latent code dimensions correlated with sensitive
attributes (e.g., gender). Nevertheless, these approaches may suffer from
incomplete disentanglement and overlook proxy attributes (proxies for sensitive
attributes) when processing real-world data, especially for unstructured data,
causing performance degradation in fairness and loss of useful information for
downstream tasks. In this paper, we propose a novel fairness framework that
performs debiasing with regard to both sensitive attributes and proxy
attributes, which boosts the prediction performance of downstream task models
without complete disentanglement. The main idea is to, first, leverage
gradient-based explanation to find two model focuses, 1) one focus for
predicting sensitive attributes and 2) the other focus for predicting
downstream task labels, and second, use them to perturb the latent code that
guides the training of downstream task models towards fairness and utility
goals. We show empirically that our framework works with both disentangled and
non-disentangled representation learning methods and achieves better
fairness-accuracy trade-off on unstructured and structured datasets than
previous state-of-the-art approaches
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