A Unifying Framework for Sparse Gaussian Process Approximation using Power Expectation Propagation Dr. Richard E. Turner ( ret26@cam.ac.uk ) Computational and Biological Learning Lab, Department of Engineering, University of Cambridge ...joint work with Thang Bui, Cuong Nguyen and Josiah Yan 1 / 22
Motivation: Gaussian Process Regression outputs inputs 2 / 22
Motivation: Gaussian Process Regression ? outputs inputs 2 / 22
Motivation: Gaussian Process Regression ? outputs inputs 2 / 22
Motivation: Gaussian Process Regression inference & learning ? outputs inputs 2 / 22
Motivation: Gaussian Process Regression inference & learning intractabilities computational analytic ? outputs inputs 2 / 22
A Brief History of Gaussian Process Approximations FITC: Snelson et al. “Sparse Gaussian Processes using Pseudo-inputs” PITC: Snelson et al. “Local and global sparse Gaussian process approximations” EP: Csato and Opper 2002 / Qi et al. "Sparse-posterior Gaussian Processes for general likelihoods.” VFE: Titsias “Variational Learning of Inducing Variables in Sparse Gaussian Processes” DTC / PP: Seeger et al. “Fast Forward Selection to Speed Up Sparse Gaussian Process Regression” 3 / 22
A Brief History of Gaussian Process Approximations approximate generative model exact inference FITC: Snelson et al. “Sparse Gaussian Processes using Pseudo-inputs” PITC: Snelson et al. “Local and global sparse Gaussian process approximations” EP: Csato and Opper 2002 / Qi et al. "Sparse-posterior Gaussian Processes for general likelihoods.” VFE: Titsias “Variational Learning of Inducing Variables in Sparse Gaussian Processes” DTC / PP: Seeger et al. “Fast Forward Selection to Speed Up Sparse Gaussian Process Regression” 3 / 22
A Brief History of Gaussian Process Approximations approximate generative model methods employing exact inference pseudo-data FITC: Snelson et al. “Sparse Gaussian Processes using Pseudo-inputs” PITC: Snelson et al. “Local and global sparse Gaussian process approximations” EP: Csato and Opper 2002 / Qi et al. "Sparse-posterior Gaussian Processes for general likelihoods.” VFE: Titsias “Variational Learning of Inducing Variables in Sparse Gaussian Processes” DTC / PP: Seeger et al. “Fast Forward Selection to Speed Up Sparse Gaussian Process Regression” 3 / 22
A Brief History of Gaussian Process Approximations approximate generative model methods employing exact inference pseudo-data FITC PITC DTC FITC: Snelson et al. “Sparse Gaussian Processes using Pseudo-inputs” PITC: Snelson et al. “Local and global sparse Gaussian process approximations” EP: Csato and Opper 2002 / Qi et al. "Sparse-posterior Gaussian Processes for general likelihoods.” VFE: Titsias “Variational Learning of Inducing Variables in Sparse Gaussian Processes” DTC / PP: Seeger et al. “Fast Forward Selection to Speed Up Sparse Gaussian Process Regression” 3 / 22
A Brief History of Gaussian Process Approximations approximate generative model methods employing exact inference pseudo-data A Unifying View of Sparse Approximate Gaussian Process Regression FITC Quinonero-Candela & PITC Rasmussen, 2005 (FITC, PITC, DTC) DTC FITC: Snelson et al. “Sparse Gaussian Processes using Pseudo-inputs” PITC: Snelson et al. “Local and global sparse Gaussian process approximations” EP: Csato and Opper 2002 / Qi et al. "Sparse-posterior Gaussian Processes for general likelihoods.” VFE: Titsias “Variational Learning of Inducing Variables in Sparse Gaussian Processes” DTC / PP: Seeger et al. “Fast Forward Selection to Speed Up Sparse Gaussian Process Regression” 3 / 22
A Brief History of Gaussian Process Approximations approximate generative model exact generative model methods employing exact inference approximate inference pseudo-data A Unifying View of Sparse Approximate Gaussian Process Regression FITC Quinonero-Candela & PITC Rasmussen, 2005 (FITC, PITC, DTC) DTC FITC: Snelson et al. “Sparse Gaussian Processes using Pseudo-inputs” PITC: Snelson et al. “Local and global sparse Gaussian process approximations” EP: Csato and Opper 2002 / Qi et al. "Sparse-posterior Gaussian Processes for general likelihoods.” VFE: Titsias “Variational Learning of Inducing Variables in Sparse Gaussian Processes” DTC / PP: Seeger et al. “Fast Forward Selection to Speed Up Sparse Gaussian Process Regression” 3 / 22
A Brief History of Gaussian Process Approximations approximate generative model exact generative model methods employing exact inference approximate inference pseudo-data A Unifying View of Sparse Approximate Gaussian Process Regression FITC VFE Quinonero-Candela & PITC EP Rasmussen, 2005 (FITC, PITC, DTC) DTC PP FITC: Snelson et al. “Sparse Gaussian Processes using Pseudo-inputs” PITC: Snelson et al. “Local and global sparse Gaussian process approximations” EP: Csato and Opper 2002 / Qi et al. "Sparse-posterior Gaussian Processes for general likelihoods.” VFE: Titsias “Variational Learning of Inducing Variables in Sparse Gaussian Processes” DTC / PP: Seeger et al. “Fast Forward Selection to Speed Up Sparse Gaussian Process Regression” 3 / 22
A Brief History of Gaussian Process Approximations approximate generative model exact generative model methods employing exact inference approximate inference pseudo-data A Unifying View of Sparse Approximate Gaussian Process Regression FITC VFE Quinonero-Candela & PITC EP Rasmussen, 2005 (FITC, PITC, DTC) DTC PP FITC: Snelson et al. “Sparse Gaussian Processes using Pseudo-inputs” PITC: Snelson et al. “Local and global sparse Gaussian process approximations” EP: Csato and Opper 2002 / Qi et al. "Sparse-posterior Gaussian Processes for general likelihoods.” VFE: Titsias “Variational Learning of Inducing Variables in Sparse Gaussian Processes” DTC / PP: Seeger et al. “Fast Forward Selection to Speed Up Sparse Gaussian Process Regression” 3 / 22
A Brief History of Gaussian Process Approximations approximate generative model exact generative model methods employing exact inference approximate inference pseudo-data A Unifying View of Sparse Approximate Gaussian Process Regression FITC VFE Quinonero-Candela & PITC EP Rasmussen, 2005 (FITC, PITC, DTC) DTC PP A Unifying Framework for Sparse Gaussian Process Approximation using Power Expectation Propagation Bui, Yan and Turner, 2016 (VFE, EP, FITC, PITC ...) FITC: Snelson et al. “Sparse Gaussian Processes using Pseudo-inputs” PITC: Snelson et al. “Local and global sparse Gaussian process approximations” EP: Csato and Opper 2002 / Qi et al. "Sparse-posterior Gaussian Processes for general likelihoods.” VFE: Titsias “Variational Learning of Inducing Variables in Sparse Gaussian Processes” DTC / PP: Seeger et al. “Fast Forward Selection to Speed Up Sparse Gaussian Process Regression” 3 / 22
EP pseudo-point approximation true posterior 4 / 22
EP pseudo-point approximation true posterior 4 / 22
EP pseudo-point approximation marginal posterior likelihood true posterior 4 / 22
EP pseudo-point approximation marginal posterior likelihood true posterior approximate posterior 4 / 22
EP pseudo-point approximation marginal posterior likelihood true posterior approximate posterior 4 / 22
EP pseudo-point approximation marginal posterior likelihood true posterior approximate posterior 4 / 22
EP pseudo-point approximation marginal posterior likelihood true posterior approximate posterior 4 / 22
EP pseudo-point approximation exact joint of new GP regression model marginal posterior likelihood true posterior approximate posterior input locations of outputs and covariance 'pseudo' data 'pseudo' data 4 / 22
EP algorithm 5 / 22
EP algorithm take out one 1. remove pseudo-observation likelihood cavity 5 / 22
EP algorithm take out one 1. remove pseudo-observation likelihood cavity add in one 2. include true observation likelihood tilted 5 / 22
EP algorithm take out one 1. remove pseudo-observation likelihood cavity add in one 2. include true observation likelihood KL between unnormalised tilted stochastic processes project onto 3. project approximating family 5 / 22
EP algorithm take out one 1. remove pseudo-observation likelihood cavity add in one 2. include true observation likelihood KL between unnormalised tilted stochastic processes project onto 3. project approximating family update 4. update pseudo-observation likelihood 5 / 22
EP algorithm take out one 1. remove pseudo-observation likelihood cavity add in one 2. include true observation likelihood KL between unnormalised tilted stochastic processes project onto 3. project approximating family 1. minimum: moments matched at pseudo-inputs 2. Gaussian regression: matches moments everywhere update 4. update pseudo-observation likelihood 5 / 22
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