deepgp Package

Maintainer: Annie S. Booth (annie_booth@ncsu.edu)

Performs Bayesian posterior inference for deep Gaussian processes following Sauer, Gramacy, and Higdon (2023). See Sauer (2023) for comprehensive methodological details and https://bitbucket.org/gramacylab/deepgp-ex/ for a variety of coding examples. Models are trained through MCMC including elliptical slice sampling of latent Gaussian layers and Metropolis-Hastings sampling of kernel hyperparameters. Vecchia-approximation for faster computation is implemented following Sauer, Cooper, and Gramacy (2023). Downstream tasks include sequential design through active learning Cohn/integrated mean squared error (ALC/IMSE; Sauer, Gramacy, and Higdon, 2023), optimization through expected improvement (EI; Gramacy, Sauer, and Wycoff, 2022), and contour location through entropy (Booth, Renganathan, and Gramacy, 2024). Models extend up to three layers deep; a one layer model is equivalent to typical Gaussian process regression. Incorporates OpenMP and SNOW parallelization and utilizes C/C++ under the hood.

Run help("deepgp-package") or help(package = "deepgp") for more information.

References

Sauer, A. (2023). Deep Gaussian process surrogates for computer experiments. Ph.D. Dissertation, Department of Statistics, Virginia Polytechnic Institute and State University. http://hdl.handle.net/10919/114845

Sauer, A., Gramacy, R.B., & Higdon, D. (2023). Active learning for deep Gaussian process surrogates. Technometrics, 65, 4-18. arXiv:2012.08015

Sauer, A., Cooper, A., & Gramacy, R. B. (2023). Vecchia-approximated deep Gaussian processes for computer experiments. Journal of Computational and Graphical Statistics, 1-14. arXiv:2204.02904

Gramacy, R. B., Sauer, A. & Wycoff, N. (2022). Triangulation candidates for Bayesian optimization. Advances in Neural Information Processing Systems (NeurIPS), 35, 35933-35945. arXiv:2112.07457

Booth, A., Renganathan, S. A. & Gramacy, R. B. (2024). Contour location for reliability in airfoil simulation experiments using deep Gaussian processes. In Review. arXiv:2308.04420

Version History

What’s new in version 1.1.2?

• Option for user to specify ordering for Vecchia approximation (through ordering argument in fit functions)
• lite = TRUE predictions have been sped up
  • bypassing the cov(t(mu_t)) computation altogether (this is only necessary for lite = FALSE)
  • removing d_new calculations
  • using diag_quad_mat Cpp function more often
• Expected improvement is now available for Vecchia-approximated fits
• Internally, predict functions have been consolidated (removing nearly 500 lines of redundant code)
• Removed internal clean_prediction function as it was no longer needed
• Minor bug fixes
  • Fixed error in fit_one_layer with vecchia = TRUE and sep = TRUE caused by the arma::mat covmat initialization in the vecchia.cpp file
  • Fixed error in predict.dgp2 with return_all = TRUE (replaced out with object - thanks Steven Barnett!)
  • Fixed storage of ll in continue functions (thanks Sebastien Coube!)

What’s new in version 1.1.1?

• Entropy calculations for contour locating sequential designs are offered through the specification of an entropy_limit in any of the predict functions.
• In posterior predictions, there is now an option to return point-wise mean and variance estimates for all MCMC samples through the specification of return_all = TRUE.
• To save on memory and storage, predict functions no longer return s2_smooth or Sigma_smooth. If desired, these quantities may be calculated by subtracting tau2 * g from the diagonal.
• The vecchia = TRUE option may now utilize either the Matern (cov = "matern") or squared exponential kernel (cov = "exp2"").
• Performance improvements for cores = 1 in predict, ALC, and IMSE functions (helps to avoid a SNOW conflict when running multiple instances on the same machine).
• Fit functions now return the outer log likelihood value along with MCMC samples. Used in trace plots to assess burn-in.
• In fit_two_layer, the intermediate latent layer may now have either a prior mean of zero (default) or a prior mean equal to x (pmx = TRUE). If pmx is set to a constant, this will be the scale parameter on the inner Gaussian layer.

What’s new in version 1.1.0?

• Package vignette
• Option to specify sep = TRUE in fit_one_layer to fit a GP with separable/anisotropic lengthscales.
• Default cores in predict are now 1 (this avoids a conflict when running multiple sessions simultaneously on a single machine).

What’s new in version 1.0.1?

• Minor bug fixes/improvements.
• New warning message when OpenMP parallelization is not utilized for the Vecchia approximation. This happens when the package is downloaded from CRAN on a Mac. To set up OpenMP, download package source and compile with gcc/g++ instead of clang.

What’s new in version 1.0.0?

• Models may now leverage the Vecchia approximation (through the specification of vecchia = TRUE in fit functions) for faster computation. The speed of this implementation relies on OpenMP parallelization (make sure the -fopenmp flag is present with package installation).
• SNOW parallelization now uses less memory/storage.
• tau2 is now calculated at the time of MCMC, not at the time of prediction. This avoids some extra calculations.

What’s new in version 0.3.0?

• The Matern kernel is now the default covariance. The smoothness parameter is user-adjustable but must be either v = 0.5, v = 1.5, or v = 2.5 (default). The squared exponential kernel is still required for use with ALC and IMSE (set cov = "exp2" in fit functions).
• Expected improvement (EI) may now be computed concurrently with predictions. Set EI = TRUE inside predict calls. EI calculations are nugget-free and are for minimizing the response (negate y if maximization is desired).
• To save memory, hidden layer mappings used in predictions are no longer stored and returned by default. To store them, set store_latent = TRUE inside predict.