arXiv subjects

Riccardo Doyle

Publications and source records attributed to Riccardo Doyle.

3 recordsLinked to original sources

arXiv2025

Enhancing Performance and Calibration in Quantile Hyperparameter Optimization

Bayesian hyperparameter optimization relies heavily on Gaussian Process (GP) surrogates, due to robust distributional posteriors and strong performance on limited training samples. GPs however underperform in categorical hyperparameter environments or when assumptions of normality, heteroskedasticity and symmetry are excessively challenged. Conformalized quantile regression can address these estimation weaknesses, while still providing robust calibration guarantees. This study builds upon early work in this area by addressing feedback covariate shift in sequential acquisition and integrating a wider range of surrogate architectures and acquisition functions. Proposed algorithms are rigorously benchmarked against a range of state of the art hyperparameter optimization methods (GP, TPE and SMAC). Findings identify quantile surrogate architectures and acquisition functions yielding superior performance to the current quantile literature, while validating the beneficial impact of conformalization on calibration and search performance.

cs.LG↗

arXiv2023

ACHO: Adaptive Conformal Hyperparameter Optimization

Several novel frameworks for hyperparameter search have emerged in the last decade, but most rely on strict, often normal, distributional assumptions, limiting search model flexibility. This paper proposes a novel optimization framework based on upper confidence bound sampling of conformal confidence intervals, whose weaker assumption of exchangeability enables greater choice of search model architectures. Several such architectures were explored and benchmarked on hyperparameter search of random forests and convolutional neural networks, displaying satisfactory interval coverage and superior tuning performance to random search.

cs.LG↗

arXiv2020

Using Network Interbank Contagion in Bank Default Prediction

Interbank contagion can theoretically exacerbate losses in a financial system and lead to additional cascade defaults during downturn. In this paper we produce default analysis using both regression and neural network models to verify whether interbank contagion offers any predictive explanatory power on default events. We predict defaults of U.S. domiciled commercial banks in the first quarter of 2010 using data from the preceding four quarters. A number of established predictors (such as Tier 1 Capital Ratio and Return on Equity) are included alongside contagion to gauge if the latter adds significance. Based on this methodology, we conclude that interbank contagion is extremely explanatory in default prediction, often outperforming more established metrics, in both regression and neural network models. These findings have sizeable implications for the future use of interbank contagion as a variable of interest for stress testing, bank issued bond valuation and wider bank default prediction.

q-fin.RM↗