protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
_spriteBatch.Begin();
for (int y = 0; y < G.GetSize(); y++)
{
for (int x = 0; x < G.GetSize(); x++)
{
int v = G.GetAtom(x, y);
Color pc = ColorMap[v];
_spriteBatch.Draw(OnePx, new Rectangle(x * CellWidth, y * CellHeight, CellWidth, CellHeight), pc);
}
}
_spriteBatch.End();
{
// Do some simulated annealing.
// Putting this in Update method ruins the animation due to large computation time.
for (int i = 0; i < G.GetSize() * G.GetSize() * 10; i++)
{
SA.AnnealStep();
}
// Slowly reduce temperature but don't allow it to go too low.
if (SA.T > 0.1)
{
SA.T *= 0.99f;
}
}
base.Draw(gameTime);
}
public int AnnealStep()
{
// 1. Get current known energy
int energy = G.GetSystemEnergy();
// 2. Preturb the system
// Let's pick 2 random locations and swap them.
int x1 = R.Next(0, G.GetSize());
int y1 = R.Next(0, G.GetSize());
int x2 = R.Next(0, G.GetSize());
int y2 = R.Next(0, G.GetSize());
int oldState1 = G.GetAtom(x1, y1);
int oldState2 = G.GetAtom(x2, y2);
G.SetAtom(x1, y1, oldState2);
G.SetAtom(x2, y2, oldState1);
int deltaE = G.GetSystemEnergy() - energy;
// Negative delta E is good, keep the state change.
// This part is the metropolis algorithm.
if (deltaE > 0)
{
float r = (float)R.NextDouble();
float p = (float)Math.Pow(Math.E, -deltaE / T); // Probablity we take the perturbation.
if (r >= p)
{
// Reject the perturbation. Restore the prev state
G.SetAtom(x1, y1, oldState1);
G.SetAtom(x2, y2, oldState2);
return(0);
}
}
return(deltaE);
}
