/// <summary>
/// Sets the value for the specified gene on the given child,
/// respecting its parents and the latest parameter origin.
/// </summary>
/// <param name="node">
/// Specifies the gene to set the value for.
/// Is allowed to be an <see cref="AndNode" />. In this case, nothing happens.
/// </param>
/// <param name="parent1">The first parent.</param>
/// <param name="parent2">The second parent.</param>
/// <param name="child">The child. Genome will be modified.</param>
/// <param name="lastParameterOrigin">
/// The latest parameter origin.
/// Influences the probability which parent's gene the child inherits.
/// </param>
/// <returns>
/// The origin of the inherited gene value.
/// For an <see cref="AndNode" />, returns the given parameter origin.
/// </returns>
private ParameterOrigin SetGeneValue(
IParameterTreeNode node,
Genome parent1,
Genome parent2,
Genome child,
ParameterOrigin lastParameterOrigin = ParameterOrigin.Open)
{
// If the node is not a parameter node, we do not have to set a value.
// The parameter origin does not change.
var nodeAsParameter = node as IParameterNode;
if (nodeAsParameter == null)
{
return(lastParameterOrigin);
}
// If it is a parameter node, find the parents' gene values.
var parameterName = nodeAsParameter.Identifier;
var parent1GeneValue = parent1.GetGeneValue(parameterName);
var parent2GeneValue = parent2.GetGeneValue(parameterName);
// If they are equal and the last parameter's origin is open, set child's parameter value to it
// and keep the origin.
if (lastParameterOrigin == ParameterOrigin.Open && object.Equals(parent1GeneValue, parent2GeneValue))
{
child.SetGene(parameterName, parent1GeneValue);
return(lastParameterOrigin);
}
// Otherwise, randomly decide on one of the two parents.
// The probability for the parents is dependent on the last parameter's origin.
double probabilityForFirstParent;
switch (lastParameterOrigin)
{
case ParameterOrigin.FirstParent:
probabilityForFirstParent = 1 - this._crossoverSwitchProbability;
break;
case ParameterOrigin.SecondParent:
probabilityForFirstParent = this._crossoverSwitchProbability;
break;
case ParameterOrigin.Open:
probabilityForFirstParent = 0.5;
break;
default:
throw new ArgumentException($"Parameter origin {lastParameterOrigin} is unknown.");
}
// Throw a (biased) coin and decide on one parent to inherit the gene value from.
var useFirstParent = Randomizer.Instance.Decide(probabilityForFirstParent);
if (useFirstParent)
{
child.SetGene(parameterName, parent1GeneValue);
return(ParameterOrigin.FirstParent);
}
child.SetGene(parameterName, parent2GeneValue);
return(ParameterOrigin.SecondParent);
}
/// <summary>
/// Initializes a new instance of the <see cref="Genome"/> class.
/// </summary>
/// <param name="genome">The genome to copy.</param>
/// <param name="age">The age of the created genome.</param>
/// <exception cref="ArgumentOutOfRangeException">Thrown if the specified age is negative.</exception>
public Genome(Genome genome, int age)
: this(genome)
{
this.Age = age;
}
/// <summary>
/// Decides whether the given genome is valid by calling <see cref="CheckAgainstParameterTree(Genome)" />.
/// </summary>
/// <param name="genome">The genome to test.</param>
/// <returns>False if the genome is invalid.</returns>
public virtual bool IsGenomeValid(Genome genome)
{
return(this.CheckAgainstParameterTree(genome));
}
