Tony O'Hagan - Resources

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The GEM Software Project


The Gaussian Emulation Machine (GEM) software project aims to provide user-friendly tools to implement statistical analyses of uncertainty in the outputs of computer models, using the techniques of Gaussian process emulation. To download an introduction to these tools and the concepts that underlie them, click here.

The GEM software available here has been developed by Marc Kennedy for the Centre for Terrestrial Carbon Dynamics (CTCD). CTCD is funded by the Natural Environment Research Council (NERC).


GEM-SA

The Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) is the first product of the GEM project. It will allow you to build an emulator of a computer code from a set of input and output points. It will also perform prediction, uncertainty analysis and sensitivity analysis of the code using far fewer code runs than Monte-Carlo based methods.

GEM-SA is offered free of charge, provided it is not used for profit. It may be freely copied and distributed, provided that files have not been edited or altered in any way, and provided that no charge is made for distributing GEM-SA. Published work that uses GEM-SA results should include a citation for this web page. Requests to use GEM-SA for any commercial purpose must be directed to Marc Kennedy.

If you use GEM-SA please let Marc Kennedy know (marc.kennedy@fera.gsi.gov.uk) and he will add you to the list of users. He will keep registered users informed of bug fixes and updated information about GEM-SA and future developments of the GEM project.

GEM-SA runs on Windows, but Linux users can also run it. The required package (called "Wine") can be freely downloaded in both binary and source form for various Linux distributions from http://www.winehq.com/site/download.

Tutorials

A course was held on March 21st and March 22nd 2005 for NERC related researchers, which included instruction in the use of GEM-SA. This was revised and given again for Engineers at the University of Sheffield on January 30th and 31st 2008. It has been revised again and updated for a course aimed at researchers in the biological sciences given on July 3rd 2008. The practical sessions (PowerPoint) have been made available for download here since the 2005 course, and the revised 2008 versions below now fully reflect the changes in GEM-SA that were implemented in version 1.1:

The course also included the following presentation about the underlying concepts and modellng choices for building emulators:

This is one of several courses offered by Tony O'Hagan and colleagues. Please use the "Contact me" button at the bottom of this page to enquire about when this course may be offered again.

Download instructions

Download V1.1 zip file (1.3MB) MS Windows version.

Extract/unzip the zip file to produce a directory GEM-SA containing the following:

The wxWindows toolkit was used for creating the GUI


GEM-Cal

The second product of the GEM project will be GEM-Cal, which will implement the calibration theory of Kennedy and O'Hagan. A beta test version of GEM-Cal may be downloaded here. Installation is similar to the procedure above for GEM-SA. Please contact Marc Kennedy for further information.


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Updated: 1 November 2009
Maintained by: Tony O'Hagan