Search Results for author: Ömer Deniz Akyildiz

Found 17 papers, 3 papers with code

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.

Adaptively Optimised Adaptive Importance Samplers

no code implementations18 Jul 2023 Carlos A. C. C. Perello, Ömer Deniz Akyildiz

We introduce a new class of adaptive importance samplers leveraging adaptive optimisation tools, which we term AdaOAIS.

Random Grid Neural Processes for Parametric Partial Differential Equations

no code implementations26 Jan 2023 Arnaud Vadeboncoeur, Ieva Kazlauskaite, Yanni Papandreou, Fehmi Cirak, Mark Girolami, Ömer Deniz Akyildiz

We introduce a new class of spatially stochastic physics and data informed deep latent models for parametric partial differential equations (PDEs) which operate through scalable variational neural processes.

Fully probabilistic deep models for forward and inverse problems in parametric PDEs

no code implementations9 Aug 2022 Arnaud Vadeboncoeur, Ömer Deniz Akyildiz, Ieva Kazlauskaite, Mark Girolami, Fehmi Cirak

In the posited probabilistic model, both the forward and inverse maps are approximated as Gaussian distributions with a mean and covariance parameterized by deep neural networks.

Variational Inference

Global convergence of optimized adaptive importance samplers

no code implementations2 Jan 2022 Ömer Deniz Akyildiz

We analyze the optimized adaptive importance sampler (OAIS) for performing Monte Carlo integration with general proposals.

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

VarGrad: A Low-Variance Gradient Estimator for Variational Inference

1 code implementation NeurIPS 2020 Lorenz Richter, Ayman Boustati, Nikolas Nüsken, Francisco J. R. Ruiz, Ömer Deniz Akyildiz

We analyse the properties of an unbiased gradient estimator of the ELBO for variational inference, based on the score function method with leave-one-out control variates.

Variational Inference

Generalized Bayesian Filtering via Sequential Monte Carlo

no code implementations23 Feb 2020 Ayman Boustati, Ömer Deniz Akyildiz, Theodoros Damoulas, Adam M. Johansen

We introduce a framework for inference in general state-space hidden Markov models (HMMs) under likelihood misspecification.

Bayesian Inference Object Tracking

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

Probabilistic sequential matrix factorization

1 code implementation9 Oct 2019 Ömer Deniz Akyildiz, Gerrit J. J. van den Burg, Theodoros Damoulas, Mark F. J. Steel

In particular, we consider nonlinear Gaussian state-space models where sequential approximate inference results in the factorization of a data matrix into a dictionary and time-varying coefficients with potentially nonlinear Markovian dependencies.

Multivariate Time Series Forecasting Multivariate Time Series Imputation +1

Convergence rates for optimised adaptive importance samplers

no code implementations28 Mar 2019 Ömer Deniz Akyildiz, Joaquín Míguez

The non-asymptotic bounds derived in this paper imply that when the target belongs to the exponential family, the $L_2$ errors of the optimised samplers converge to the optimal rate of $\mathcal{O}(1/\sqrt{N})$ and the rate of convergence in the number of iterations are explicitly provided.

A probabilistic incremental proximal gradient method

no code implementations4 Dec 2018 Ömer Deniz Akyildiz, Émilie Chouzenoux, Víctor Elvira, Joaquín Míguez

In this paper, we propose a probabilistic optimization method, named probabilistic incremental proximal gradient (PIPG) method, by developing a probabilistic interpretation of the incremental proximal gradient algorithm.

Parallel sequential Monte Carlo for stochastic gradient-free nonconvex optimization

no code implementations23 Nov 2018 Ömer Deniz Akyildiz, Dan Crisan, Joaquín Míguez

We introduce and analyze a parallel sequential Monte Carlo methodology for the numerical solution of optimization problems that involve the minimization of a cost function that consists of the sum of many individual components.

Stochastic Optimization

The Incremental Proximal Method: A Probabilistic Perspective

no code implementations12 Jul 2018 Ömer Deniz Akyildiz, Victor Elvira, Joaquin Miguez

We then carry out this observation to a general sequential setting: We consider the incremental proximal method, which is an algorithm for large-scale optimization, and show that, for a linear-quadratic cost function, it can naturally be realized by the Kalman filter.

regression

Matrix Factorisation with Linear Filters

no code implementations7 Sep 2015 Ömer Deniz Akyildiz

Using the probabilistic model, we derive a matrix factorisation algorithm as a recursive linear filter.

Image Restoration

Online Matrix Factorization via Broyden Updates

no code implementations14 Jun 2015 Ömer Deniz Akyildiz

In this paper, we propose an online algorithm to compute matrix factorizations.

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