16 research outputs found
BOCK : Bayesian Optimization with Cylindrical Kernels
A major challenge in Bayesian Optimization is the boundary issue (Swersky,
2017) where an algorithm spends too many evaluations near the boundary of its
search space. In this paper, we propose BOCK, Bayesian Optimization with
Cylindrical Kernels, whose basic idea is to transform the ball geometry of the
search space using a cylindrical transformation. Because of the transformed
geometry, the Gaussian Process-based surrogate model spends less budget
searching near the boundary, while concentrating its efforts relatively more
near the center of the search region, where we expect the solution to be
located. We evaluate BOCK extensively, showing that it is not only more
accurate and efficient, but it also scales successfully to problems with a
dimensionality as high as 500. We show that the better accuracy and scalability
of BOCK even allows optimizing modestly sized neural network layers, as well as
neural network hyperparameters.Comment: 10 pages, 5 figures, 5 tables, 1 algorith
Combinatorial Bayesian Optimization using the Graph Cartesian Product
This paper focuses on Bayesian Optimization (BO) for objectives on
combinatorial search spaces, including ordinal and categorical variables.
Despite the abundance of potential applications of Combinatorial BO, including
chipset configuration search and neural architecture search, only a handful of
methods have been proposed. We introduce COMBO, a new Gaussian Process (GP) BO.
COMBO quantifies "smoothness" of functions on combinatorial search spaces by
utilizing a combinatorial graph. The vertex set of the combinatorial graph
consists of all possible joint assignments of the variables, while edges are
constructed using the graph Cartesian product of the sub-graphs that represent
the individual variables. On this combinatorial graph, we propose an ARD
diffusion kernel with which the GP is able to model high-order interactions
between variables leading to better performance. Moreover, using the Horseshoe
prior for the scale parameter in the ARD diffusion kernel results in an
effective variable selection procedure, making COMBO suitable for high
dimensional problems. Computationally, in COMBO the graph Cartesian product
allows the Graph Fourier Transform calculation to scale linearly instead of
exponentially. We validate COMBO in a wide array of realistic benchmarks,
including weighted maximum satisfiability problems and neural architecture
search. COMBO outperforms consistently the latest state-of-the-art while
maintaining computational and statistical efficiency.Comment: Accepted to NeurIPS 2019, code: https://github.com/QUVA-Lab/COMB
Major medical causes by breed and life stage for dogs presented at veterinary clinics in the Republic of Korea: a survey of electronic medical records
Background Age and breed are considered the greatest risk factors for disease prevalence and mortality in companion dogs. Understanding the prevalence of diseases, in relation to age and breed, would support appropriate guidance for future health care strategies and provide useful information for the early diagnosis of diseases. The purpose of this study was to investigate the major medical causes for dogs visiting primary-care veterinary clinics in the Republic of Korea, stratified by age and breed. Methods A total of 15,531 medical records of canine patients were analyzed from 11 veterinary clinics who shared data from January 1, 2016 to December 31, 2016. An electronic medical record (EMR) system was used for data collection, which included the animal identification number, age, breed, gender, neuter status, clinical information, and diagnosis. EMR data were classified using the International Classification of Disease system from the World Health Organization; presenting signs or diagnoses were identified according to breed and life stage. Results Within the age groups, preventive medicine (16.7% confidence intervals (CI) [15.9–17.5]) was the most common cause for clinic visits for the 10 year), the prevalences of heart disease, kidney disease, Cushing’s disease, and mammary tumors were higher than in the other age groups. Small and toy breed dogs comprised 67.7% of all dogs in this analysis. For all breeds, otitis externa, dermatitis or eczema, vomiting, and diarrhea were common medical problems. Discussion This study identified the most common medical disorders and differences in prevalences of diseases, according to age and breeds. The information from EMRs for dogs visiting primary-care veterinary clinics can provide background knowledge that is required to enable a better understanding of disease patterns and occurrence by age and breeds. The information from this study could enable the creation of strategies for preventing diseases and enable the identification of health problems for more effective disease management in companion dogs
A Practical Approach to International Monetary System Reform: Building Settlement Infrastructure for Regional Currencies
Regional Settlement Infrastructure and Currency Internationalization: The Case of Asia and the Renminbi
Radial and Directional Posteriors for Bayesian Deep Learning
We propose a new variational family for Bayesian neural networks. We decompose the variational posterior into two components, where the radial component captures the strength of each neuron in terms of its magnitude; while the directional component captures the statistical dependencies among the weight parameters. The dependencies learned via the directional density provide better modeling performance compared to the widely-used Gaussian mean-field-type variational family. In addition, the strength of input and output neurons learned via our posterior provides a structured way to compress neural networks. Indeed, experiments show that our variational family improves predictive performance and yields compressed networks simultaneously
Mixed Variable Bayesian Optimization with Frequency Modulated Kernels
The sample efficiency of Bayesian optimization(BO) is often boosted by
Gaussian Process(GP) surrogate models. However, on mixed variable spaces,
surrogate models other than GPs are prevalent, mainly due to the lack of
kernels which can model complex dependencies across different types of
variables. In this paper, we propose the frequency modulated (FM) kernel
flexibly modeling dependencies among different types of variables, so that BO
can enjoy the further improved sample efficiency. The FM kernel uses distances
on continuous variables to modulate the graph Fourier spectrum derived from
discrete variables. However, the frequency modulation does not always define a
kernel with the similarity measure behavior which returns higher values for
pairs of more similar points. Therefore, we specify and prove conditions for FM
kernels to be positive definite and to exhibit the similarity measure behavior.
In experiments, we demonstrate the improved sample efficiency of GP BO using FM
kernels (BO-FM).On synthetic problems and hyperparameter optimization problems,
BO-FM outperforms competitors consistently. Also, the importance of the
frequency modulation principle is empirically demonstrated on the same
problems. On joint optimization of neural architectures and SGD
hyperparameters, BO-FM outperforms competitors including Regularized
evolution(RE) and BOHB. Remarkably, BO-FM performs better even than RE and BOHB
using three times as many evaluations.Comment: Proceedings of the Thirty-Seventh Conference on Uncertainty in
Artificial Intelligence, PMLR 161:950-960, 202
Batch Bayesian Optimization on Permutations using Acquisition Weighted Kernels
In this work we propose a batch Bayesian optimization method for
combinatorial problems on permutations, which is well suited for expensive cost
functions on permutations. We introduce LAW, a new efficient batch acquisition
method based on the determinantal point process, using an acquisition weighted
kernel. Relying on multiple parallel evaluations, LAW accelerates the search
for the optimal permutation. We provide a regret analysis for our method to
gain insight in its theoretical properties. We then apply the framework to
permutation problems, which have so far received little attention in the
Bayesian Optimization literature, despite their practical importance. We call
this method LAW2ORDER. We evaluate the method on several standard combinatorial
problems involving permutations such as quadratic assignment, flowshop
scheduling and the traveling salesman, as well as on a structure learning task
Nitric Oxide Emission Reduction in Reheating Furnaces through Burner and Furnace Air-Staged Combustions
In this study, a series of experiments were conducted on a testing facility and a real-scale furnace, for analyzing the nitric oxide (NO) emission reduction. The effects of the temperature, oxygen concentration, and amount of secondary combustion air were investigated in a single-burner combustion system. Additionally, the NO-reduction rate before and after combustion modifications in both the burner and furnace air-staged combustion were evaluated for a real-scale reheating furnace. The air-to-fuel equivalence ratio (λ) of individual combustion zones for the furnace was optimized for NO reduction without any incomplete combustion. The results indicated that the NO emission for controlling the λ of a single-zone decreased linearly with a decrease in the λ values in the individual firing tests (top-heat, bottom-heat, and bottom-soak zones). Moreover, the multi-zone control of the λ values for individual combustion zones was optimized at 1.13 (top-preheat), 1.0 (bottom-preheat), 1.0 (top-heat), 0.97 (bottom-heat), 1.0 (top-soak), and 0.97 (bottom-soak). In this firing condition, the modifications reduced the NO emissions by approximately 23%, as indicated by a comparison of the data obtained before and after the modifications. Thus, the combined application of burner and furnace air-staged combustions facilitated NO-emission reduction