Goto

Collaborating Authors

 Uncertainty


Improving Diffusion Models for Inverse Problems using Manifold Constraints

arXiv.org Artificial Intelligence

Recently, diffusion models have been used to solve various inverse problems in an unsupervised manner with appropriate modifications to the sampling process. However, the current solvers, which recursively apply a reverse diffusion step followed by a projection-based measurement consistency step, often produce suboptimal results. By studying the generative sampling path, here we show that current solvers throw the sample path off the data manifold, and hence the error accumulates. To address this, we propose an additional correction term inspired by the manifold constraint, which can be used synergistically with the previous solvers to make the iterations close to the manifold. The proposed manifold constraint is straightforward to implement within a few lines of code, yet boosts the performance by a surprisingly large margin. With extensive experiments, we show that our method is superior to the previous methods both theoretically and empirically, producing promising results in many applications such as image inpainting, colorization, and sparse-view computed tomography.


Movement Analytics: Current Status, Application to Manufacturing, and Future Prospects from an AI Perspective

arXiv.org Artificial Intelligence

Data-driven decision making is becoming an integral part of manufacturing companies. Data is collected and commonly used to improve efficiency and produce high quality items for the customers. IoT-based and other forms of object tracking are an emerging tool for collecting movement data of objects/entities (e.g. human workers, moving vehicles, trolleys etc.) over space and time. Movement data can provide valuable insights like process bottlenecks, resource utilization, effective working time etc. that can be used for decision making and improving efficiency. Turning movement data into valuable information for industrial management and decision making requires analysis methods. We refer to this process as movement analytics. The purpose of this document is to review the current state of work for movement analytics both in manufacturing and more broadly. We survey relevant work from both a theoretical perspective and an application perspective. From the theoretical perspective, we put an emphasis on useful methods from two research areas: machine learning, and logic-based knowledge representation. We also review their combinations in view of movement analytics, and we discuss promising areas for future development and application. Furthermore, we touch on constraint optimization. From an application perspective, we review applications of these methods to movement analytics in a general sense and across various industries. We also describe currently available commercial off-the-shelf products for tracking in manufacturing, and we overview main concepts of digital twins and their applications.


Convergence of score-based generative modeling for general data distributions

arXiv.org Artificial Intelligence

Diffusion models have gained huge popularity in recent years in machine learning, as a method to learn and generate new samples from a data distribution. Score-based generative modeling (SGM), as a particular kind of diffusion model, uses learned score functions (gradients of the log-pdf) to transform white noise to the data distribution through following a stochatic differential equation. While SGM has achieved state-of-theart performance for artificial image and audio generation [SE19; Dat+19; Gra+19; SE20; Son+20; Men+21; Son+21b; Son+21a; Jin+22], including being a key component of text-to-image systems [Ram+22], our theoretical understanding of these models is still nascent. In particular, basic questions on the convergence of the generated distribution to the data distribution remain unanswered. Recent theoretical work on SGM has attempted to answer these questions [De +21; LLT22; De 22], but they either suffer from exponential dependence on parameters or rely on strong assumptions on the data distribution such as functional inequalities or smoothness, which are rarely satisfied in practical situations. For example, considering the hallmark application of generating images from text, we expect the distribution of images to be (a) multimodal, and hence not satisfying functional inequalities with reasonable constants, and (b) supported on lower-dimensional manifolds, and hence not smooth. However, SGM still performs remarkably well in these settings. Indeed, this is one relative advantage to other approaches to generative modeling such as generative adversarial networks, which can struggle to learn multimodal distributions [ARZ18]. In this work, we aim to develop theoretical convergence guarantees with polynomial complexity for SGM under minimal data assumptions.


Belief propagation generalizes backpropagation

arXiv.org Artificial Intelligence

The two most important algorithms in artificial intelligence are backpropagation and belief propagation. In spite of their importance, the connection between them is poorly characterized. We show that when an input to backpropagation is converted into an input to belief propagation so that (loopy) belief propagation can be run on it, then the result of belief propagation encodes the result of backpropagation; thus backpropagation is recovered as a special case of belief propagation. In other words, we prove for apparently the first time that belief propagation generalizes backpropagation. Our analysis is a theoretical contribution, which we motivate with the expectation that it might reconcile our understandings of each of these algorithms, and serve as a guide to engineering researchers seeking to improve the behavior of systems that use one or the other.


Computer Vision - Richard Szeliski

#artificialintelligence

As humans, we perceive the three-dimensional structure of the world around us with apparent ease. Think of how vivid the three-dimensional percept is when you look at a vase of flowers sitting on the table next to you. You can tell the shape and translucency of each petal through the subtle patterns of light and shading that play across its surface and effortlessly segment each flower from the background of the scene (Figure 1.1). Looking at a framed group por- trait, you can easily count (and name) all of the people in the picture and even guess at their emotions from their facial appearance. Perceptual psychologists have spent decades trying to understand how the visual system works and, even though they can devise optical illusions1 to tease apart some of its principles (Figure 1.3), a complete solution to this puzzle remains elusive (Marr 1982; Palmer 1999; Livingstone 2008).


Disentangling Mixtures of Unknown Causal Interventions

arXiv.org Artificial Intelligence

In many real-world scenarios, such as gene knockout experiments, targeted interventions are often accompanied by unknown interventions at off-target sites. Moreover, different units can get randomly exposed to different unknown interventions, thereby creating a mixture of interventions. Identifying different components of this mixture can be very valuable in some applications. Motivated by such situations, in this work, we study the problem of identifying all components present in a mixture of interventions on a given causal Bayesian Network. We construct an example to show that, in general, the components are not identifiable from the mixture distribution. Next, assuming that the given network satisfies a positivity condition, we show that, if the set of mixture components satisfy a mild exclusion assumption, then they can be uniquely identified. Our proof gives an efficient algorithm to recover these targets from the exponentially large search space of possible targets. In the more realistic scenario, where distributions are given via finitely many samples, we conduct a simulation study to analyze the performance of an algorithm derived from our identifiability proof.


Bayesian Q-learning With Imperfect Expert Demonstrations

arXiv.org Artificial Intelligence

Guided exploration with expert demonstrations improves data efficiency for reinforcement learning, but current algorithms often overuse expert information. We propose a novel algorithm to speed up Q-learning with the help of a limited amount of imperfect expert demonstrations. The algorithm avoids excessive reliance on expert data by relaxing the optimal expert assumption and gradually reducing the usage of uninformative expert data. Experimentally, we evaluate our approach on a sparse-reward chain environment and six more complicated Atari games with delayed rewards. With the proposed methods, we can achieve better results than Deep Q-learning from Demonstrations (Hester et al., 2017) in most environments.


Design of Economical Fuzzy Logic Controller for Washing Machine

arXiv.org Artificial Intelligence

Things are becoming more advanced as technology advances, and machines now perform the majority of the manual work. The most often used home appliance is the washing machine for cloths. Modification and research in this field is essential since it pertains to the amount of time, water, and electricity required for washing. In this work, a Fuzzy Logic Controller has been developed for smart washing machines. The objective of this paper is to optimize the consumption of electricity, water, and detergent for washing machines. The type of dirt, volume of clothes, and type of cloth play a vital role in saving water, electricity, and detergent. However, none of the work on the Fuzzy Logic Controller provided a design procedure endowed with the specified inputs and outputs implemented in Python. In this paper, we used the Mamdani approach and created an algorithm based on multi-input multi-output. The algorithm is implemented in Python. The results of this simulation show that the washing machine provides better execution at a low computation cost.


Statistical Properties of the log-cosh Loss Function Used in Machine Learning

arXiv.org Artificial Intelligence

This paper analyzes a popular loss function used in machine learning called the log-cosh loss function. A number of papers have been published using this loss function but, to date, no statistical analysis has been presented in the literature. In this paper, we present the distribution function from which the log-cosh loss arises. We compare it to a similar distribution, called the Cauchy distribution, and carry out various statistical procedures that characterize its properties. In particular, we examine its associated pdf, cdf, likelihood function and Fisher information. Side-by-side we consider the Cauchy and Cosh distributions as well as the MLE of the location parameter with asymptotic bias, asymptotic variance, and confidence intervals. We also provide a comparison of robust estimators from several other loss functions, including the Huber loss function and the rank dispersion function. Further, we examine the use of the log-cosh function for quantile regression. In particular, we identify a quantile distribution function from which a maximum likelihood estimator for quantile regression can be derived. Finally, we compare a quantile M-estimator based on log-cosh with robust monotonicity against another approach to quantile regression based on convolutional smoothing.


Swift Markov Logic for Probabilistic Reasoning on Knowledge Graphs

arXiv.org Artificial Intelligence

We provide a framework for probabilistic reasoning in Vadalog-based Knowledge Graphs (KGs), satisfying the requirements of ontological reasoning: full recursion, powerful existential quantification, expression of inductive definitions. Vadalog is a Knowledge Representation and Reasoning (KRR) language based on Warded Datalog+/-, a logical core language of existential rules, with a good balance between computational complexity and expressive power. Handling uncertainty is essential for reasoning with KGs. Yet Vadalog and Warded Datalog+/- are not covered by the existing probabilistic logic programming and statistical relational learning approaches for several reasons, including insufficient support for recursion with existential quantification, and the impossibility to express inductive definitions. In this work, we introduce Soft Vadalog, a probabilistic extension to Vadalog, satisfying these desiderata. A Soft Vadalog program induces what we call a Probabilistic Knowledge Graph (PKG), which consists of a probability distribution on a network of chase instances, structures obtained by grounding the rules over a database using the chase procedure. We exploit PKGs for probabilistic marginal inference. We discuss the theory and present MCMC-chase, a Monte Carlo method to use Soft Vadalog in practice. We apply our framework to solve data management and industrial problems, and experimentally evaluate it in the Vadalog system.