/// <summary>
/// Performs a single throw onto a roulette wheel where the wheel's space is unevenly divided between outcomes.
/// The probabilty that a segment will be selected is given by that segment's value in the 'probabilities'
/// array within the specified RouletteWheelLayout. The probabilities within a RouletteWheelLayout have already
/// been normalised so that their total is always equal to 1.0.
/// </summary>
/// <param name="layout">The roulette wheel layout.</param>
/// <param name="rng">Random number generator.</param>
public static int SingleThrow(RouletteWheelLayout layout, FastRandom rng)
{
// Throw the ball and return an integer indicating the outcome.
double throwValue = layout.ProbabilitiesTotal * rng.NextDouble();
double accumulator = 0.0;
for(int i=0; i<layout.Probabilities.Length; i++)
{
accumulator += layout.Probabilities[i];
if(throwValue < accumulator) {
return layout.Labels[i];
}
}
// We might get here through floating point arithmetic rounding issues.
// e.g. accumulator == throwValue.
// Find a nearby non-zero probability to select.
// Wrap around to start of array.
for(int i=0; i<layout.Probabilities.Length; i++)
{
if(layout.Probabilities[i] != 0.0) {
return layout.Labels[i];
}
}
// If we get here then we have an array of zero probabilities.
throw new SharpNeatException("Invalid operation. No non-zero probabilities to select.");
}
/// <summary>
/// Genetic mutation for auxiliary argument data.
/// </summary>
public void MutateAuxArgs(double[] auxArgs, FastRandom rng, ZigguratGaussianSampler gaussianSampler, double connectionWeightRange)
{
throw new SharpNeatException("MutateAuxArgs() called on activation function that does not use auxiliary arguments.");
}
/// <summary>
/// For activation functions that accept auxiliary arguments; generates random initial values for aux arguments for newly
/// added nodes (from an 'add neuron' mutation).
/// </summary>
public double[] GetRandomAuxArgs(FastRandom rng, double connectionWeightRange)
{
throw new SharpNeatException("GetRandomAuxArgs() called on activation function that does not use auxiliary arguments.");
}
/// <summary>
/// Gets the single NEAT activation function provided at construction time.
/// The provided random number generator is not used in this implementation.
/// </summary>
/// <param name="rng"></param>
/// <returns></returns>
public ActivationFunctionInfo GetRandomFunction(FastRandom rng)
{
return _activationFnInfo;
}
/// <summary>
/// Performs a single throw for a given number of outcomes with equal probabilities.
/// </summary>
/// <param name="numberOfOutcomes">The number of possible outcomes.</param>
/// <param name="rng">Random number generator.</param>
/// <returns>An integer between 0..numberOfOutcomes-1. In effect this routine selects one of the possible outcomes.</returns>
public static int SingleThrowEven(int numberOfOutcomes, FastRandom rng)
{
return (int)(rng.NextDouble() * numberOfOutcomes);
}
/// <summary>
/// A simple single throw routine.
/// </summary>
/// <param name="probability">A probability between 0..1 that the throw will result in a true result.</param>
/// <param name="rng">Random number generator.</param>
public static bool SingleThrow(double probability, FastRandom rng)
{
return rng.NextDouble() < probability;
}
/// <summary>
/// Default constructor.
/// </summary>
public TestCaseField()
{
_rng = new FastRandom();
}
/// <summary>
/// Randomly select a function based on each function's selection probability.
/// </summary>
public ActivationFunctionInfo GetRandomFunction(FastRandom rng)
{
return _functionList[RouletteWheel.SingleThrow(_rwl, rng)];
}