Statistical Learning
GeoAdaLer: Geometric Insights into Adaptive Stochastic Gradient Descent Algorithms
Eleh, Chinedu, Mwanza, Masuzyo, Aguegboh, Ekene, van Wyk, Hans-Werner
The Adam optimization method has achieved remarkable success in addressing contemporary challenges in stochastic optimization. This method falls within the realm of adaptive sub-gradient techniques, yet the underlying geometric principles guiding its performance have remained shrouded in mystery, and have long confounded researchers. In this paper, we introduce GeoAdaLer (Geometric Adaptive Learner), a novel adaptive learning method for stochastic gradient descent optimization, which draws from the geometric properties of the optimization landscape. Beyond emerging as a formidable contender, the proposed method extends the concept of adaptive learning by introducing a geometrically inclined approach that enhances the interpretability and effectiveness in complex optimization scenarios.
Position: Why We Must Rethink Empirical Research in Machine Learning
Herrmann, Moritz, Lange, F. Julian D., Eggensperger, Katharina, Casalicchio, Giuseppe, Wever, Marcel, Feurer, Matthias, Rรผgamer, David, Hรผllermeier, Eyke, Boulesteix, Anne-Laure, Bischl, Bernd
In practice, that leads to non-replicable results, makes it may jeopardize applied empirical researchers' confidence findings unreliable, and threatens to undermine in experimental results and discourage them from applying progress in the field. To overcome this alarming ML methods, even though these novel approaches might be situation, we call for more awareness of the beneficial. For example, ML is increasingly being used in plurality of ways of gaining knowledge experimentally the medical domain, and this is often promising in terms of but also of some epistemic limitations.
Risk Factor Identification In Osteoporosis Using Unsupervised Machine Learning Techniques
In this study, the reliability of identified risk factors associated with osteoporosis is investigated using a new clustering-based method on electronic medical records. This study proposes utilizing a new CLustering Iterations Framework (CLIF) that includes an iterative clustering framework that can adapt any of the following three components: clustering, feature selection, and principal feature identification. The study proposes using Wasserstein distance to identify principal features, borrowing concepts from the optimal transport theory. The study also suggests using a combination of ANOVA and ablation tests to select influential features from a data set. Some risk factors presented in existing works are endorsed by our identified significant clusters, while the reliability of some other risk factors is weakened.
Recasting Generic Pretrained Vision Transformers As Object-Centric Scene Encoders For Manipulation Policies
Qian, Jianing, Panagopoulos, Anastasios, Jayaraman, Dinesh
Generic re-usable pre-trained image representation encoders have become a standard component of methods for many computer vision tasks. As visual representations for robots however, their utility has been limited, leading to a recent wave of efforts to pre-train robotics-specific image encoders that are better suited to robotic tasks than their generic counterparts. We propose Scene Objects From Transformers, abbreviated as SOFT, a wrapper around pre-trained vision transformer (PVT) models that bridges this gap without any further training. Rather than construct representations out of only the final layer activations, SOFT individuates and locates object-like entities from PVT attentions, and describes them with PVT activations, producing an object-centric embedding. Across standard choices of generic pre-trained vision transformers PVT, we demonstrate in each case that policies trained on SOFT(PVT) far outstrip standard PVT representations for manipulation tasks in simulated and real settings, approaching the state-of-the-art robotics-aware representations. Code, appendix and videos: https://sites.google.com/view/robot-soft/
Dissecting the Interplay of Attention Paths in a Statistical Mechanics Theory of Transformers
Tiberi, Lorenzo, Mignacco, Francesca, Irie, Kazuki, Sompolinsky, Haim
Despite the remarkable empirical performance of Transformers, their theoretical understanding remains elusive. Here, we consider a deep multi-head self-attention network, that is closely related to Transformers yet analytically tractable. We develop a statistical mechanics theory of Bayesian learning in this model, deriving exact equations for the network's predictor statistics under the finite-width thermodynamic limit, i.e., $N,P\rightarrow\infty$, $P/N=\mathcal{O}(1)$, where $N$ is the network width and $P$ is the number of training examples. Our theory shows that the predictor statistics are expressed as a sum of independent kernels, each one pairing different 'attention paths', defined as information pathways through different attention heads across layers. The kernels are weighted according to a 'task-relevant kernel combination' mechanism that aligns the total kernel with the task labels. As a consequence, this interplay between attention paths enhances generalization performance. Experiments confirm our findings on both synthetic and real-world sequence classification tasks. Finally, our theory explicitly relates the kernel combination mechanism to properties of the learned weights, allowing for a qualitative transfer of its insights to models trained via gradient descent. As an illustration, we demonstrate an efficient size reduction of the network, by pruning those attention heads that are deemed less relevant by our theory.
Derivatives of Stochastic Gradient Descent
Iutzeler, Franck, Pauwels, Edouard, Vaiter, Samuel
The differentiation of iterative algorithms has been a subject of research since the 1990s (Gilbert, 1992; Christianson, 1994; Beck, 1994), and was succinctly described as "piggyback differentiation" by Griewank and Faure (2003). This idea has gained renewed interest within the machine learning community, particularly for applications such as hyperparameter optimization (Maclaurin et al., 2015; Franceschi et al., 2017), metalearning (Finn et al., 2017; Rajeswaran et al., 2019), and learning discretization of total variation (Chambolle and Pock, 2021; Bogensperger et al., 2022). When applied to an optimization problem, an important theoretical concern is the convergence of the derivatives of iterates to the derivatives of the solution. Traditional guarantees focus on asymptotic convergence to the solution derivative, as described by the implicit function theorem (Gilbert, 1992; Christianson, 1994; Beck, 1994). This issue has inspired recent works for smooth optimization algorithms (Mehmood and Ochs, 2020, 2022), generic nonsmooth iterations (Bolte et al., 2022), and second-order methods (Bolte et al., 2023).
E2Vec: Feature Embedding with Temporal Information for Analyzing Student Actions in E-Book Systems
Miyazaki, Yuma, ล vรกbenskรฝ, Valdemar, Taniguchi, Yuta, Okubo, Fumiya, Minematsu, Tsubasa, Shimada, Atsushi
Digital textbook (e-book) systems record student interactions with textbooks as a sequence of events called EventStream data. In the past, researchers extracted meaningful features from EventStream, and utilized them as inputs for downstream tasks such as grade prediction and modeling of student behavior. Previous research evaluated models that mainly used statistical-based features derived from EventStream logs, such as the number of operation types or access frequencies. While these features are useful for providing certain insights, they lack temporal information that captures fine-grained differences in learning behaviors among different students. This study proposes E2Vec, a novel feature representation method based on word embeddings. The proposed method regards operation logs and their time intervals for each student as a string sequence of characters and generates a student vector of learning activity features that incorporates time information. We applied fastText to generate an embedding vector for each of 305 students in a dataset from two years of computer science courses. Then, we investigated the effectiveness of E2Vec in an at-risk detection task, demonstrating potential for generalizability and performance.
Towards a Probabilistic Fusion Approach for Robust Battery Prognostics
Alcibar, Jokin, Aizpurua, Jose I., Zugasti, Ekhi
In this context, robust and reliable battery Batteries are a key enabling technology for the decarbonization prognostics models support the development of accurate of transport and energy sectors. The estimation of the state-of-health (SOH) of batteries is a In this direction, the development of accurate and robust battery key activity for the design of RUL prognostics models. SOHbased state-of-health prognostics models can unlock the potential prognostics models focus on capturing the run-to-failure of autonomous systems for complex, remote and reliable ageing dynamics and battery health state estimation (Toughzaoui operations. It is frequently used to determine age-related modelling concepts and ensemble learning strategies, form degradation that reduces energy capacity and rises safety risks, a valuable prognostics framework to combine uncertainty in including overheating and explosions (Wang et al., 2022). Accordingly, this paper introduces Therefore, accurate SOH monitoring and forecasting are key a Bayesian ensemble learning approach to predict activities to design and operate safe, reliable and effective the capacity depletion of lithium-ion batteries. SOH estimation is an ongoing area of research (Yang, Chen, The proposed Bayesian ensemble methodology employs Chen, & Huang, 2023). SOH refers to the ratio of the current a stacking technique, integrating multiple Bayesian neural maximum capacity relative to its original specified capacity networks (BNNs) as base learners, which have been trained (X. SOH can be quantified on data diversity.
Dimension-free deterministic equivalents for random feature regression
Defilippis, Leonardo, Loureiro, Bruno, Misiakiewicz, Theodor
In this work we investigate the generalization performance of random feature ridge regression (RFRR). Our main contribution is a general deterministic equivalent for the test error of RFRR. Specifically, under a certain concentration property, we show that the test error is well approximated by a closed-form expression that only depends on the feature map eigenvalues. Notably, our approximation guarantee is non-asymptotic, multiplicative, and independent of the feature map dimension -- allowing for infinite-dimensional features. We expect this deterministic equivalent to hold broadly beyond our theoretical analysis, and we empirically validate its predictions on various real and synthetic datasets. As an application, we derive sharp excess error rates under standard power-law assumptions of the spectrum and target decay. In particular, we provide a tight result for the smallest number of features achieving optimal minimax error rate.
Towards Precision Healthcare: Robust Fusion of Time Series and Image Data
Rasekh, Ali, Heidari, Reza, Rezaie, Amir Hosein Haji Mohammad, Sedeh, Parsa Sharifi, Ahmadi, Zahra, Mitra, Prasenjit, Nejdl, Wolfgang
With the increasing availability of diverse data types, particularly images and time series data from medical experiments, there is a growing demand for techniques designed to combine various modalities of data effectively. Our motivation comes from the important areas of predicting mortality and phenotyping where using different modalities of data could significantly improve our ability to predict. To tackle this challenge, we introduce a new method that uses two separate encoders, one for each type of data, allowing the model to understand complex patterns in both visual and time-based information. Apart from the technical challenges, our goal is to make the predictive model more robust in noisy conditions and perform better than current methods. We also deal with imbalanced datasets and use an uncertainty loss function, yielding improved results while simultaneously providing a principled means of modeling uncertainty. Additionally, we include attention mechanisms to fuse different modalities, allowing the model to focus on what's important for each task. We tested our approach using the comprehensive multimodal MIMIC dataset, combining MIMIC-IV and MIMIC-CXR datasets. Our experiments show that our method is effective in improving multimodal deep learning for clinical applications. The code will be made available online.