10,012 research outputs found
UMSL Bulletin 2023-2024
The 2023-2024 Bulletin and Course Catalog for the University of Missouri St. Louis.https://irl.umsl.edu/bulletin/1088/thumbnail.jp
Non-parametric online market regime detection and regime clustering for multidimensional and path-dependent data structures
In this work we present a non-parametric online market regime detection
method for multidimensional data structures using a path-wise two-sample test
derived from a maximum mean discrepancy-based similarity metric on path space
that uses rough path signatures as a feature map. The latter similarity metric
has been developed and applied as a discriminator in recent generative models
for small data environments, and has been optimised here to the setting where
the size of new incoming data is particularly small, for faster reactivity.
On the same principles, we also present a path-wise method for regime
clustering which extends our previous work. The presented regime clustering
techniques were designed as ex-ante market analysis tools that can identify
periods of approximatively similar market activity, but the new results also
apply to path-wise, high dimensional-, and to non-Markovian settings as well as
to data structures that exhibit autocorrelation.
We demonstrate our clustering tools on easily verifiable synthetic datasets
of increasing complexity, and also show how the outlined regime detection
techniques can be used as fast on-line automatic regime change detectors or as
outlier detection tools, including a fully automated pipeline. Finally, we
apply the fine-tuned algorithms to real-world historical data including
high-dimensional baskets of equities and the recent price evolution of crypto
assets, and we show that our methodology swiftly and accurately indicated
historical periods of market turmoil.Comment: 65 pages, 52 figure
Networked Time Series Prediction with Incomplete Data
A networked time series (NETS) is a family of time series on a given graph,
one for each node. It has a wide range of applications from intelligent
transportation, environment monitoring to smart grid management. An important
task in such applications is to predict the future values of a NETS based on
its historical values and the underlying graph. Most existing methods require
complete data for training. However, in real-world scenarios, it is not
uncommon to have missing data due to sensor malfunction, incomplete sensing
coverage, etc. In this paper, we study the problem of NETS prediction with
incomplete data. We propose NETS-ImpGAN, a novel deep learning framework that
can be trained on incomplete data with missing values in both history and
future. Furthermore, we propose Graph Temporal Attention Networks, which
incorporate the attention mechanism to capture both inter-time series and
temporal correlations. We conduct extensive experiments on four real-world
datasets under different missing patterns and missing rates. The experimental
results show that NETS-ImpGAN outperforms existing methods, reducing the MAE by
up to 25%
EmbedDistill: A Geometric Knowledge Distillation for Information Retrieval
Large neural models (such as Transformers) achieve state-of-the-art
performance for information retrieval (IR). In this paper, we aim to improve
distillation methods that pave the way for the resource-efficient deployment of
such models in practice. Inspired by our theoretical analysis of the
teacher-student generalization gap for IR models, we propose a novel
distillation approach that leverages the relative geometry among queries and
documents learned by the large teacher model. Unlike existing teacher
score-based distillation methods, our proposed approach employs embedding
matching tasks to provide a stronger signal to align the representations of the
teacher and student models. In addition, it utilizes query generation to
explore the data manifold to reduce the discrepancies between the student and
the teacher where training data is sparse. Furthermore, our analysis also
motivates novel asymmetric architectures for student models which realizes
better embedding alignment without increasing online inference cost. On
standard benchmarks like MSMARCO, we show that our approach successfully
distills from both dual-encoder (DE) and cross-encoder (CE) teacher models to
1/10th size asymmetric students that can retain 95-97% of the teacher
performance
An advanced deep learning models-based plant disease detection: A review of recent research
Plants play a crucial role in supplying food globally. Various environmental factors lead to plant diseases which results in significant production losses. However, manual detection of plant diseases is a time-consuming and error-prone process. It can be an unreliable method of identifying and preventing the spread of plant diseases. Adopting advanced technologies such as Machine Learning (ML) and Deep Learning (DL) can help to overcome these challenges by enabling early identification of plant diseases. In this paper, the recent advancements in the use of ML and DL techniques for the identification of plant diseases are explored. The research focuses on publications between 2015 and 2022, and the experiments discussed in this study demonstrate the effectiveness of using these techniques in improving the accuracy and efficiency of plant disease detection. This study also addresses the challenges and limitations associated with using ML and DL for plant disease identification, such as issues with data availability, imaging quality, and the differentiation between healthy and diseased plants. The research provides valuable insights for plant disease detection researchers, practitioners, and industry professionals by offering solutions to these challenges and limitations, providing a comprehensive understanding of the current state of research in this field, highlighting the benefits and limitations of these methods, and proposing potential solutions to overcome the challenges of their implementation
Modular lifelong machine learning
Deep learning has drastically improved the state-of-the-art in many important fields, including computer vision and natural language processing (LeCun et al., 2015). However, it is expensive to train a deep neural network on a machine learning problem. The overall training cost further increases when one wants to solve additional problems. Lifelong machine learning (LML) develops algorithms that aim to efficiently learn to solve a sequence of problems, which become available one at a time. New problems are solved with less resources by transferring previously learned knowledge. At the same time, an LML algorithm needs to retain good performance on all encountered problems, thus avoiding catastrophic forgetting. Current approaches do not possess all the desired properties of an LML algorithm. First, they primarily focus on preventing catastrophic forgetting (Diaz-Rodriguez et al., 2018; Delange et al., 2021). As a result, they neglect some knowledge transfer properties. Furthermore, they assume that all problems in a sequence share the same input space. Finally, scaling these methods to a large sequence of problems remains a challenge.
Modular approaches to deep learning decompose a deep neural network into sub-networks, referred to as modules. Each module can then be trained to perform an atomic transformation, specialised in processing a distinct subset of inputs. This modular approach to storing knowledge makes it easy to only reuse the subset of modules which are useful for the task at hand.
This thesis introduces a line of research which demonstrates the merits of a modular approach to lifelong machine learning, and its ability to address the aforementioned shortcomings of other methods. Compared to previous work, we show that a modular approach can be used to achieve more LML properties than previously demonstrated. Furthermore, we develop tools which allow modular LML algorithms to scale in order to retain said properties on longer sequences of problems.
First, we introduce HOUDINI, a neurosymbolic framework for modular LML. HOUDINI represents modular deep neural networks as functional programs and accumulates a library of pre-trained modules over a sequence of problems. Given a new problem, we use program synthesis to select a suitable neural architecture, as well as a high-performing combination of pre-trained and new modules. We show that our approach has most of the properties desired from an LML algorithm. Notably, it can perform forward transfer, avoid negative transfer and prevent catastrophic forgetting, even across problems with disparate input domains and problems which require different neural architectures.
Second, we produce a modular LML algorithm which retains the properties of HOUDINI but can also scale to longer sequences of problems. To this end, we fix the choice of a neural architecture and introduce a probabilistic search framework, PICLE, for searching through different module combinations. To apply PICLE, we introduce two probabilistic models over neural modules which allows us to efficiently identify promising module combinations.
Third, we phrase the search over module combinations in modular LML as black-box optimisation, which allows one to make use of methods from the setting of hyperparameter optimisation (HPO). We then develop a new HPO method which marries a multi-fidelity approach with model-based optimisation. We demonstrate that this leads to improvement in anytime performance in the HPO setting and discuss how this can in turn be used to augment modular LML methods.
Overall, this thesis identifies a number of important LML properties, which have not all been attained in past methods, and presents an LML algorithm which can achieve all of them, apart from backward transfer
Representation Learning With Hidden Unit Clustering For Low Resource Speech Applications
The representation learning of speech, without textual resources, is an area
of significant interest for many low resource speech applications. In this
paper, we describe an approach to self-supervised representation learning from
raw audio using a hidden unit clustering (HUC) framework. The input to the
model consists of audio samples that are windowed and processed with 1-D
convolutional layers. The learned "time-frequency" representations from the
convolutional neural network (CNN) module are further processed with long short
term memory (LSTM) layers which generate a contextual vector representation for
every windowed segment. The HUC framework, allowing the categorization of the
representations into a small number of phoneme-like units, is used to train the
model for learning semantically rich speech representations. The targets
consist of phoneme-like pseudo labels for each audio segment and these are
generated with an iterative k-means algorithm. We explore techniques that
improve the speaker invariance of the learned representations and illustrate
the effectiveness of the proposed approach on two settings, i) completely
unsupervised speech applications on the sub-tasks described as part of the
ZeroSpeech 2021 challenge and ii) semi-supervised automatic speech recognition
(ASR) applications on the TIMIT dataset and on the GramVaani challenge Hindi
dataset. In these experiments, we achieve state-of-art results for various
ZeroSpeech tasks. Further, on the ASR experiments, the HUC representations are
shown to improve significantly over other established benchmarks based on
Wav2vec, HuBERT and Best-RQ
The State of the Art in Deep Learning Applications, Challenges, and Future Prospects::A Comprehensive Review of Flood Forecasting and Management
Floods are a devastating natural calamity that may seriously harm both infrastructure and people. Accurate flood forecasts and control are essential to lessen these effects and safeguard populations. By utilizing its capacity to handle massive amounts of data and provide accurate forecasts, deep learning has emerged as a potent tool for improving flood prediction and control. The current state of deep learning applications in flood forecasting and management is thoroughly reviewed in this work. The review discusses a variety of subjects, such as the data sources utilized, the deep learning models used, and the assessment measures adopted to judge their efficacy. It assesses current approaches critically and points out their advantages and disadvantages. The article also examines challenges with data accessibility, the interpretability of deep learning models, and ethical considerations in flood prediction. The report also describes potential directions for deep-learning research to enhance flood predictions and control. Incorporating uncertainty estimates into forecasts, integrating many data sources, developing hybrid models that mix deep learning with other methodologies, and enhancing the interpretability of deep learning models are a few of these. These research goals can help deep learning models become more precise and effective, which will result in better flood control plans and forecasts. Overall, this review is a useful resource for academics and professionals working on the topic of flood forecasting and management. By reviewing the current state of the art, emphasizing difficulties, and outlining potential areas for future study, it lays a solid basis. Communities may better prepare for and lessen the destructive effects of floods by implementing cutting-edge deep learning algorithms, thereby protecting people and infrastructure
Improving Heterogeneous Graph Learning with Weighted Mixed-Curvature Product Manifold
In graph representation learning, it is important that the complex geometric
structure of the input graph, e.g. hidden relations among nodes, is well
captured in embedding space. However, standard Euclidean embedding spaces have
a limited capacity in representing graphs of varying structures. A promising
candidate for the faithful embedding of data with varying structure is product
manifolds of component spaces of different geometries (spherical, hyperbolic,
or euclidean). In this paper, we take a closer look at the structure of product
manifold embedding spaces and argue that each component space in a product
contributes differently to expressing structures in the input graph, hence
should be weighted accordingly. This is different from previous works which
consider the roles of different components equally. We then propose
WEIGHTED-PM, a data-driven method for learning embedding of heterogeneous
graphs in weighted product manifolds. Our method utilizes the topological
information of the input graph to automatically determine the weight of each
component in product spaces. Extensive experiments on synthetic and real-world
graph datasets demonstrate that WEIGHTED-PM is capable of learning better graph
representations with lower geometric distortion from input data, and performs
better on multiple downstream tasks, such as word similarity learning, top-
recommendation, and knowledge graph embedding
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