1.
Open Session of the EuFMD - Cascais –Portugal 26-28 October 2016
Reducing computing times of spatially explicit
FMD models
S. Sellman, K. Tsao, M. Keeling, M. Tildesley, C. Webb, U. Wennergren, T. Lindström.

2.
Background
• Stochastic, spatially explicit farm-level models of FMD (and other infections) become
slow when populations are large.
• The reason is that there are a lot of possible events, each with very small probability
of occurring.
• This restricts what can be achieved and limits models’ scientific potential.
• 62*10^6 seconds  718 days…

3.
The solution
• Divide landscape into squares.
• Most possible transmissions never actually occur – filter those
away…
• …by checking for infection on the grid-square level first.
• Speedup: reduction of up 1-2 orders of magnitude.
• The grid configuration has a large impact on the speed.
• What is the optimum number of farms / square?
• Development of an algorithm is underway.
• Potential R-package?

4.
OS16
Questions or comments?
Come visit!
Thank you
or email Stefan Sellman:
stefan.Sellman@liu.se
Funding was provided by the Foreign Animal Disease Modeling Program, Science and Technology Directorate,
U.S. Department of Homeland Security (contract HSHQDC-13-C-B0028); and European research area: animal
health and welfare (ANIHWA; https://www.anihwa.eu) contract No. ANR-13-ANWA-0007-03 (LIVEepi).