Evolutionary modelling using the Stochastic Spatial ultimatum game.
BD_Cumulative.pde by R M L Evans
Code for simulation of model pubished at www.nature.com/articles/s41598-018-34384-w in:
"Pay-off scarcity causes evolution of risk-aversion and extreme altruism", R M L Evans, Sci. Rep (2018) 8:16074.
Coded in "processing" language, a java-based (C-derived) language, freely available at https://processing.org/
For real-time graphical output, launch the code directly from the processing IDE. To set parameters and output text, the code can be compiled and exported to an executable, then
launched from the comman line, specifying the parameters: (int)RandomNumberSeed (float)mu (float)BirthRate (int)L (boolean)HalfAndHalf (float)tmax
e.g.
.\BD_Cumulative.exe 6 0.005 100 128 false 10000.0
or, to redirect output to a text file for further analysis:
.\BD_Cumulative.exe 6 0.005 100 128 false 10000.0 > .\BD_CumulatBR100M0.008.csv
Thus a set of simulations may be run sytematically by executing a batch file such as
exampleBatchScript.bat
Algorithm of the Stochastic Spatial Ultimatum Game B-D Process (Random birth causes a fitness-dependent death):
Agents filling a square grid are chosen at random play the Ultimatum Game, making an offer to a randomly chosen one of their four immediate neighbours. The offerer is chosen stochastically at a mean rate of once per agent per timestep. Also stochastically, with a mean rate of BirthRate per agent, agents are selected randomly to reproduce. Their offspring replaces either the weakest of the parent's four neighbours (with probability SP) or a random neighbour (with probability 1-SP).
Offspring inherit none of the parent's wealth. They inherit the parent's offer and acceptance values +/- a uniformly distributed random mutation of standard deviation mu.