Simulation Framework

Question

I started creating a small abstract simulation framework and would be happy if someone could take a look at the code and give me feedback on it.

The code can be found here, and it is currently not in a 100% finished and tested state.

It should be (almost) multi threading ready.

This is some sample code on how you can use the framework:

class Program
    {
        static void Main(string[] args)
        {
            Debug.Listeners.Add(new ConsoleTraceListener());

            var system = new SimulationSystem();

            // Add a thread and a simulation engine to the simulation framework
            system.AddSimulationThread(new SimulationThread(new SimulationEngine[] {new TestSimulationEngine() }.ToList()));

            // Add a new simulation group
            system.World.Objects.Add(new SimulationGroup());

            // Add a new object to the group
            ((SimulationGroup)system.World.Objects[0]).Objects.Add(new SimulationObject());
            system.World.Objects.Add(new SimulationObject());

            DateTime loopStart = DateTime.Now;
            DateTime loopEnd = DateTime.Now;

            // Simulates the update loop
            while (true)
            {
                loopStart = DateTime.Now;
                system.Update(loopStart - loopEnd);
                loopEnd = DateTime.Now;

                // Wait for user to press enter to start the next loop
                //Console.ReadLine();
            }
        }
    }

with this TestSimulationEngine class:

public class TestSimulationEngine : SimulationEngine
{
    public override void UpdateWorld(SimulationContext context, TimeSpan step)
    {
        // Do some stuff to the simulation world

        Console.WriteLine("UpdatingWorld with step {0}", step);

        // Add a new object each loop
        context.World.Objects.Add(new SimulationObject());
    }
}

A short introduction to the architecture behind the framework:

There is the class SimulationSystem which you can use to initialise a new simulated world. You can assign SimulationEngines to defined threads. For example a physicsengine to thread 1, a heatsystem to thread 2, ...

Also it holds the SimulationWorld which is a hierarchical system. Inside the World you can add SimulationObjects and SimulationGroups. A SimulationGroup is the same as a SimulationObject but can also have sub-objects.

For example, inside the world you can add a car as a simulation group. Inside the car you have the engine, driver, etc as simulation sub-objects.

You can also set any property you want on the objects using the code object["Property"].

Answer 1

First, a general consideration about your project. I cannot see any unit test. I'd strongly encourage you to write some, as I think that unit tests can help you coming up with a better design. I haven't looked at the code in details so unfortunately I don't have other comments on that.

Looking at the example main you posted I see you should try to rewrite your code so that you do dependency injection and in a way that you don't have to violate the law of Demeter to setup the simulation.

What about changing the constructor of SimulationSystem to SimulationSystem(IEnumerable<SimulationThread> simulationThreads, IEnumerable<SimulationGroup> simulationGroups)? If you do that you make it clear what you need to run your simulation and you can avoid doing the very ugly operations involving system.World.Objects.

I am not sure what you want to do with all that calls to DateTime.Now, but they don't look quite right to me. I think that the idea of having system.Update take a TimeSpan as a parameter is good, but I would not expect it to be called in that way. What about this:

var currentDateTime = /* compute it somehow */
var endDateTime = /* compute it somehow */
var simulationTimespan = /* compute it somehow */
while(currentDateTime < endDateTime)
{
    system.Update(simulationTimespan);
    currentDateTime = currentDateTime.Add(simulationTimespan);
}