Search Results for author: Sotirios Sabanis

Found 16 papers, 4 papers with code

Taming the Interacting Particle Langevin Algorithm -- the superlinear case

no code implementations28 Mar 2024 Tim Johnston, Nikolaos Makras, Sotirios Sabanis

Recent advances in stochastic optimization have yielded the interactive particle Langevin algorithm (IPLA), which leverages the notion of interacting particle systems (IPS) to efficiently sample from approximate posterior densities.

Stochastic Optimization

On diffusion-based generative models and their error bounds: The log-concave case with full convergence estimates

no code implementations22 Nov 2023 Stefano Bruno, Ying Zhang, Dong-Young Lim, Ömer Deniz Akyildiz, Sotirios Sabanis

As a result, we obtain the best known upper bound estimates in terms of key quantities of interest, such as the dimension and rates of convergence, for the Wasserstein-2 distance between the data distribution (Gaussian with unknown mean) and our sampling algorithm.

Taming under isoperimetry

no code implementations15 Nov 2023 Iosif Lytras, Sotirios Sabanis

In this article we propose a novel taming Langevin-based scheme called $\mathbf{sTULA}$ to sample from distributions with superlinearly growing log-gradient which also satisfy a Log-Sobolev inequality.

Interacting Particle Langevin Algorithm for Maximum Marginal Likelihood Estimation

no code implementations23 Mar 2023 Ö. Deniz Akyildiz, Francesca Romana Crucinio, Mark Girolami, Tim Johnston, Sotirios Sabanis

We achieve this by formulating a continuous-time interacting particle system which can be seen as a Langevin diffusion over an extended state space of parameters and latent variables.

Kinetic Langevin MCMC Sampling Without Gradient Lipschitz Continuity -- the Strongly Convex Case

no code implementations19 Jan 2023 Tim Johnston, Iosif Lytras, Sotirios Sabanis

In this article we consider sampling from log concave distributions in Hamiltonian setting, without assuming that the objective gradient is globally Lipschitz.

Langevin dynamics based algorithm e-TH$\varepsilon$O POULA for stochastic optimization problems with discontinuous stochastic gradient

1 code implementation24 Oct 2022 Dong-Young Lim, Ariel Neufeld, Sotirios Sabanis, Ying Zhang

We introduce a new Langevin dynamics based algorithm, called e-TH$\varepsilon$O POULA, to solve optimization problems with discontinuous stochastic gradients which naturally appear in real-world applications such as quantile estimation, vector quantization, CVaR minimization, and regularized optimization problems involving ReLU neural networks.

Portfolio Optimization Quantization +2

Statistical Finite Elements via Langevin Dynamics

1 code implementation21 Oct 2021 Ömer Deniz Akyildiz, Connor Duffin, Sotirios Sabanis, Mark Girolami

Through embedding uncertainty inside of the governing equations, finite element solutions are updated to give a posterior distribution which quantifies all sources of uncertainty associated with the model.

Uncertainty Quantification

Non-asymptotic estimates for TUSLA algorithm for non-convex learning with applications to neural networks with ReLU activation function

1 code implementation19 Jul 2021 Dong-Young Lim, Ariel Neufeld, Sotirios Sabanis, Ying Zhang

To illustrate the applicability of the main results, we consider an example from transfer learning with ReLU neural networks, which represents a key paradigm in machine learning.

Stochastic Optimization Transfer Learning

Polygonal Unadjusted Langevin Algorithms: Creating stable and efficient adaptive algorithms for neural networks

1 code implementation28 May 2021 Dong-Young Lim, Sotirios Sabanis

We present a new class of Langevin based algorithms, which overcomes many of the known shortcomings of popular adaptive optimizers that are currently used for the fine tuning of deep learning models.

Stochastic Optimization

A fully data-driven approach to minimizing CVaR for portfolio of assets via SGLD with discontinuous updating

no code implementations2 Jul 2020 Sotirios Sabanis, Ying Zhang

We are thus able to provide theoretical guarantees for the algorithm's convergence in (standard) Wasserstein distances for both convex and non-convex objective functions.

Stochastic Optimization

Taming neural networks with TUSLA: Non-convex learning via adaptive stochastic gradient Langevin algorithms

no code implementations25 Jun 2020 Attila Lovas, Iosif Lytras, Miklós Rásonyi, Sotirios Sabanis

We offer a new learning algorithm based on an appropriately constructed variant of the popular stochastic gradient Langevin dynamics (SGLD), which is called tamed unadjusted stochastic Langevin algorithm (TUSLA).

Nonasymptotic analysis of Stochastic Gradient Hamiltonian Monte Carlo under local conditions for nonconvex optimization

no code implementations13 Feb 2020 Ömer Deniz Akyildiz, Sotirios Sabanis

We provide a nonasymptotic analysis of the convergence of the stochastic gradient Hamiltonian Monte Carlo (SGHMC) to a target measure in Wasserstein-2 distance without assuming log-concavity.

Bayesian Inference Generalization Bounds

Optimising portfolio diversification and dimensionality

no code implementations3 Jun 2019 Mathias Barkhagen, Brian Fleming, Sergio Garcia Quiles, Jacek Gondzio, Joerg Kalcsics, Jens Kroeske, Sotirios Sabanis, Arne Staal

It is based on a novel concept called portfolio dimensionality that connects diversification to the non-Gaussianity of portfolio returns and can typically be defined in terms of the ratio of risk measures which are homogenous functions of equal degree.

On stochastic gradient Langevin dynamics with dependent data streams: the fully non-convex case

no code implementations30 May 2019 Ngoc Huy Chau, Éric Moulines, Miklos Rásonyi, Sotirios Sabanis, Ying Zhang

We consider the problem of sampling from a target distribution, which is \emph {not necessarily logconcave}, in the context of empirical risk minimization and stochastic optimization as presented in Raginsky et al. (2017).

Stochastic Optimization

Model-Independent Price Bounds for Catastrophic Mortality Bonds

no code implementations24 Jul 2016 Raj Kumari Bahl, Sotirios Sabanis

In this paper, we are concerned with the valuation of Catastrophic Mortality Bonds and, in particular, we examine the case of the Swiss Re Mortality Bond 2003 as a primary example of this class of assets.

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