Parameter Sweeping with simulation batches
In some cases you may need to test the same simulation configuration with different parameters. Suppose for example that you want to see what happens when you place a bunch of pedestrian in a circle (for sake of semplicity we’ll ignore their behavior). You may want to observe the scenario with 50 pedestrians placed in a 5 meters radius circle. Then you may like to observe it with 100 pedestrian and perhaps by changing the circle radius also. Instead of re-writing the configuration file over-and-over for each parameter combination, Alchemist offers the possibility to write the configuration once, and it will then derive a batch of simulations.the same configuration
Launching batch simulations
To exploit this mechanism, you must declare the “parameters” as variables. In our example, they would be the number of pedestrian and the radius of the circle where to place them. Let’s write the configuration file, specifing that we want to test the simulation with 10, 30, 50, 70, 90 pedestrians and a 5, 10, 15 meters circle radius:
To understand how variables work refer to this page. You may also want to learn how to export data and specifying termination criteria.
Now we can launch the batch of simulations by providing the simulator the following command-line arguments:
-b: enable batch mode-var pedestrianNumber: all values of variablepedestrianNumberwill be tested-var circleRadius: all values of variablecircleRadiuswill be tested
Under the hood, the simulator will compute the cartesian product of the all possible values of the variables selected with the -var option.
Variables not selected for the batch will have their default value.