1. A new method for agent-based simulation dynamics analysis
“AGENTS’ EFFECTIVE NETWORK”
A new method for agent-based simulation dynamics analysis
When using conditional interaction models with pair interactions…
Agent-based simulation models are more and more used. The characterization of the model dynamics is still an important problem. We propose to use « Agents’ effective networks » as a new wiewpoint on the model that could bring usefull information to analyse its dynamics
For instance: Opinion dynamics model (Deffuant et al., 2002)
Two agents’ opinions x and x’
If |x-x’|<d
x = x + µ.(x’-x)
d = d + µ.(d’-d)
The method could also be applied to other social simulation models or ecological models with a spatial proximity constraint on the interactions
Examples taken from the study of agri-environmental measures adoption model developed within the IMAGES project on the Breadalbane region (UK). The interactions could be constrained by a spatial distance (top) or by a social network (bottom).
We can build the graph composed by the links which verify the condition at each simulation time step
(|x-x’|<u for the given example)
This method facilitates the study of the model dynamics
Number of links of the effective network through time for the opinion dynamics model given above for several values of d
Through time…
Or at a given timestep
Number of clusters of the effective network through time for the opinion dynamics model taken in example for several values of d
Betweeness centrality distribution within the effective network for the IMAGES model at convergence. Betweeness centrality exprimates the degree to which an individual is central within a graph concerning the information diffusion
Closeness centrality distribution within the effective network for the IMAGES model at convergence. Closeness centrality exprimates the degree to which an individual is close to the others within the graph
These illustrations are taken from the agri-environmental measures adoption model within the IMAGES project. Illustrating spatial constraint on network or a social constraint on network
Computational cost
to update the effective network
Is quite heavy, even if we use the effective network to schedule the entities (we then schedule only the effective relations without computing the test)
But local laws for updating the network can improve the calculation
Agent’s effective network enables to better analyse what happens within the model as it is the core support of the dynamics
F.Amblard, G.Deffuant - Cemagref-LISC :