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 Statistical Learning


Racial/Ethnic Categories in AI and Algorithmic Fairness: Why They Matter and What They Represent

arXiv.org Artificial Intelligence

Racial diversity has become increasingly discussed within the AI The utilization of racial and ethnic categories in the development and algorithmic fairness literature, yet little attention is focused on of datasets and models facilitates the inclusion and documentation justifying the choices of racial categories and understanding how of diverse perspectives. Racial and ethnic categories are especially people are racialized into these chosen racial categories. Even less crucial for datasets and models in which race and ethnicity attention is given to how racial categories shift and how the racialization serve as relevant factors, may act as confounding variables, or enable process changes depending on the context of a dataset or the ability to audit for fairness using race and ethnicity for model. An unclear understanding of who comprises the racial categories fairness purposes. For example, understanding the racial and/or chosen and how people are racialized into these categories ethnic target of hate speech is crucial for understanding the impact can lead to varying interpretations of these categories. These varying of hate speech, as hate speech can differ based on the race interpretations can lead to harm when the understanding of and/or ethnicity of the target[48]. Similarly, in health, race is correlated racial categories and the racialization process is misaligned from with health outcomes[6], and knowledge of a patient's race the actual racialization process and racial categories used. Harm and ethnicity can help contextualize the patient's experience and can also arise if the racialization process and racial categories used health history[53]. In algorithmic fairness settings, knowledge of are irrelevant ordonot exist inthecontext they areapplied.


Can Contrastive Learning Refine Embeddings

arXiv.org Artificial Intelligence

Recent advancements in contrastive learning have revolutionized self-supervised representation learning and achieved state-of-the-art performance on benchmark tasks. While most existing methods focus on applying contrastive learning to input data modalities such as images, natural language sentences, or networks, they overlook the potential of utilizing outputs from previously trained encoders. In this paper, we introduce SIMSKIP, a novel contrastive learning framework that specifically refines input embeddings for downstream tasks. Unlike traditional unsupervised learning approaches, SIMSKIP takes advantage of the output embeddings of encoder models as its input. Through theoretical analysis, we provide evidence that applying SIMSKIP does not result in larger upper bounds on downstream task errors than those of the original embeddings, which serve as SIMSKIP's input. Experimental results on various open datasets demonstrate that the embeddings produced by SIMSKIP improve performance on downstream tasks.


Representation Learning of Tangled Key-Value Sequence Data for Early Classification

arXiv.org Artificial Intelligence

Key-value sequence data has become ubiquitous and naturally appears in a variety of real-world applications, ranging from the user-product purchasing sequences in e-commerce, to network packet sequences forwarded by routers in networking. Classifying these key-value sequences is important in many scenarios such as user profiling and malicious applications identification. In many time-sensitive scenarios, besides the requirement of classifying a key-value sequence accurately, it is also desired to classify a key-value sequence early, in order to respond fast. However, these two goals are conflicting in nature, and it is challenging to achieve them simultaneously. In this work, we formulate a novel tangled key-value sequence early classification problem, where a tangled key-value sequence is a mixture of several concurrent key-value sequences with different keys. The goal is to classify each individual key-value sequence sharing a same key both accurately and early. To address this problem, we propose a novel method, i.e., Key-Value sequence Early Co-classification (KVEC), which leverages both inner- and inter-correlations of items in a tangled key-value sequence through key correlation and value correlation to learn a better sequence representation. Meanwhile, a time-aware halting policy decides when to stop the ongoing key-value sequence and classify it based on current sequence representation. Experiments on both real-world and synthetic datasets demonstrate that our method outperforms the state-of-the-art baselines significantly. KVEC improves the prediction accuracy by up to $4.7 - 17.5\%$ under the same prediction earliness condition, and improves the harmonic mean of accuracy and earliness by up to $3.7 - 14.0\%$.


Analysis of Distributed Optimization Algorithms on a Real Processing-In-Memory System

arXiv.org Artificial Intelligence

Machine Learning (ML) training on large-scale datasets is a very expensive and time-consuming workload. Processor-centric architectures (e.g., CPU, GPU) commonly used for modern ML training workloads are limited by the data movement bottleneck, i.e., due to repeatedly accessing the training dataset. As a result, processor-centric systems suffer from performance degradation and high energy consumption. Processing-In-Memory (PIM) is a promising solution to alleviate the data movement bottleneck by placing the computation mechanisms inside or near memory. Our goal is to understand the capabilities and characteristics of popular distributed optimization algorithms on real-world PIM architectures to accelerate data-intensive ML training workloads. To this end, we 1) implement several representative centralized distributed optimization algorithms on UPMEM's real-world general-purpose PIM system, 2) rigorously evaluate these algorithms for ML training on large-scale datasets in terms of performance, accuracy, and scalability, 3) compare to conventional CPU and GPU baselines, and 4) discuss implications for future PIM hardware and the need to shift to an algorithm-hardware codesign perspective to accommodate decentralized distributed optimization algorithms. Our results demonstrate three major findings: 1) Modern general-purpose PIM architectures can be a viable alternative to state-of-the-art CPUs and GPUs for many memory-bound ML training workloads, when operations and datatypes are natively supported by PIM hardware, 2) the importance of carefully choosing the optimization algorithm that best fit PIM, and 3) contrary to popular belief, contemporary PIM architectures do not scale approximately linearly with the number of nodes for many data-intensive ML training workloads. To facilitate future research, we aim to open-source our complete codebase.


Generative Resident Separation and Multi-label Classification for Multi-person Activity Recognition

arXiv.org Artificial Intelligence

This paper presents two models to address the problem of multi-person activity recognition using ambient sensors in a home. The first model, Seq2Res, uses a sequence generation approach to separate sensor events from different residents. The second model, BiGRU+Q2L, uses a Query2Label multi-label classifier to predict multiple activities simultaneously. Performances of these models are compared to a state-of-the-art model in different experimental scenarios, using a state-of-the-art dataset of two residents in a home instrumented with ambient sensors. These results lead to a discussion on the advantages and drawbacks of resident separation and multi-label classification for multi-person activity recognition.


Are EEG Sequences Time Series? EEG Classification with Time Series Models and Joint Subject Training

arXiv.org Artificial Intelligence

As with most other data domains, EEG data analysis relies on rich domain-specific preprocessing. Beyond such preprocessing, machine learners would hope to deal with such data as with any other time series data. For EEG classification many models have been developed with layer types and architectures we typically do not see in time series classification. Furthermore, typically separate models for each individual subject are learned, not one model for all of them. In this paper, we systematically study the differences between EEG classification models and generic time series classification models. We describe three different model setups to deal with EEG data from different subjects, subject-specific models (most EEG literature), subject-agnostic models and subject-conditional models. In experiments on three datasets, we demonstrate that off-the-shelf time series classification models trained per subject perform close to EEG classification models, but that do not quite reach the performance of domain-specific modeling. Additionally, we combine time-series models with subject embeddings to train one joint subject-conditional classifier on all subjects. The resulting models are competitive with dedicated EEG models in 2 out of 3 datasets, even outperforming all EEG methods on one of them.


AI-Guided Feature Segmentation Techniques to Model Features from Single Crystal Diamond Growth

arXiv.org Artificial Intelligence

Process refinement to consistently produce high-quality material over a large area of the grown crystal, enabling various applications from optics crystals to quantum detectors, has long been a goal for diamond growth. Machine learning offers a promising path toward this goal, but faces challenges such as the complexity of features within datasets, their time-dependency, and the volume of data produced per growth run. Accurate spatial feature extraction from image to image for real-time monitoring of diamond growth is crucial yet complicated due to the low-volume and high feature complexity nature of the datasets. This paper compares various traditional and machine learning-driven approaches for feature extraction in the diamond growth domain, proposing a novel deep learning-driven semantic segmentation approach to isolate and classify accurate pixel masks of geometric features like diamond, pocket holder, and background, along with their derivative features based on shape and size. Using an annotation-focused human-in-the-loop software architecture for training datasets, with modules for selective data labeling using active learning, data augmentations, and model-assisted labeling, our approach achieves effective annotation accuracy and drastically reduces labeling time and cost. Deep learning algorithms prove highly efficient in accurately learning complex representations from datasets with many features. Our top-performing model, based on the DeeplabV3plus architecture, achieves outstanding accuracy in classifying features of interest, with accuracies of 96.31% for pocket holder, 98.60% for diamond top, and 91.64% for diamond side features.


Formation-Controlled Dimensionality Reduction

arXiv.org Artificial Intelligence

Dimensionality reduction represents the process of extracting low dimensional structure from high dimensional data. High dimensional data include multimedia databases, gene expression microarrays, and financial time series, for example. In order to deal with such real-world data properly, it is better to reduce its dimensionality to avoid undesired properties of high dimensions such as the curse of dimensionality [14, 11]. As a result, classification, visualization, and compression of data can be expedited, for example [14]. In many problems, it is presumed that the dimensionality of the measured data is only artificially high; the measured data are high-dimensional but data nearly have a lower-dimensional structure, since they are multiple, indirect measurements of an underlying factors, which typically cannot be directly calibrated [4].


The Sample Complexity of Gradient Descent in Stochastic Convex Optimization

arXiv.org Artificial Intelligence

Stochastic Convex Optimization (SCO) is a theoretical model that depicts a learner that minimizes a (Lipschitz) convex function, given finite noisy observations of the objective [22]. While often considered simplistic, in recent years SCO has become a focus of theoretical research, partly, because of its importance to the study of first-order optimization methods. But, also, it has become focus of study because it is one of few theoretical settings that exhibit overparameterized learning. In more detail, classical learning theory often focuses on the tension between number of samples, or training data, and the complexity of the model to be learnt. A common wisdom of classical theories [1, 7, 14, 24] is that, to avoid overfitting, the complexity of a model should be adjusted in proportion to the amount of training data. However, recent advances in Machine Learning have challenged this viewpoint. Evidently [18, 25], state-of-the-art algorithms generalize well but without, explicitly, controlling the capacity of the model to be learnt. In turn, today, it is one of the most emerging challenges, for learning theory, to understand learnability when the number of parameters in a learnt model exceeds the number of examples, and when, seemingly, nothing withholds the algorithm from overfitting. Towards this, we look at SCO.


Error Mitigation for TDoA UWB Indoor Localization using Unsupervised Machine Learning

arXiv.org Artificial Intelligence

Indoor positioning systems based on Ultra-wideband (UWB) technology are gaining recognition for their ability to provide cm-level localization accuracy. However, these systems often encounter challenges caused by dense multi-path fading, leading to positioning errors. To address this issue, in this letter, we propose a novel methodology for unsupervised anchor node selection using deep embedded clustering (DEC). Our approach uses an Auto Encoder (AE) before clustering, thereby better separating UWB features into separable clusters of UWB input signals. We furthermore investigate how to rank these clusters based on their cluster quality, allowing us to remove untrustworthy signals. Experimental results show the efficiency of our proposed method, demonstrating a significant 23.1% reduction in mean absolute error (MAE) compared to without anchor exclusion. Especially in the dense multi-path area, our algorithm achieves even more significant enhancements, reducing the MAE by 26.6% and the 95th percentile error by 49.3% compared to without anchor exclusion.