/// <summary>
/// Mutates a genome by breaking a connection up into two separate connections.
/// </summary>
/// <param name="genome">The genome to be modified.</param>
/// <param name="innovationsSeen">A list of previously seen innovations.</param>
/// <param name="rando">A random number generator.</param>
public static void MutateAddNode(Genome genome, InnovationPool innovationsSeen, Random rando)
{
List <Gene> possibleConnections = new List <Gene>(genome.Genes);
possibleConnections.RemoveAll(x => x.Frozen || NodePool.FindById(x.link.InNode).Type == NodeType.BIAS);
if (possibleConnections.Count == 0)
{
return;
}
//TODO: Note in original algorithm saying uniform distribution is not optimal here.
Gene geneToSplit = possibleConnections[rando.Next(possibleConnections.Count)];
geneToSplit.Frozen = true;
ActivationStyle style = ActivationFunctions.ChooseActivationStyle(rando);
InnovationInformation innovation = new InnovationInformation(geneToSplit.link, style);
int firstConId = -1;
int secondConId = -1;
int registeredInnovationId = innovationsSeen.FindByInnovation(innovation);
if (registeredInnovationId == -1)
{
int newNodeId = NodePool.Add(new NodeInformation(NodeType.HIDDEN, style));
ConnectionInformation firstConnect = new ConnectionInformation(geneToSplit.link.InNode, newNodeId);
firstConId = ConnectionPool.Add(firstConnect);
ConnectionInformation secondConnect = new ConnectionInformation(newNodeId, geneToSplit.link.OutNode);
secondConId = ConnectionPool.Add(secondConnect);
innovation.NewNodeDetails.NewNodeId = newNodeId;
innovation.NewNodeDetails.FirstConnectionId = firstConId;
innovation.NewNodeDetails.SecondConnectionId = secondConId;
innovationsSeen.Add(innovation);
}
else
{
InnovationInformation registeredInnovation = innovationsSeen.FindById(registeredInnovationId);
firstConId = registeredInnovation.NewNodeDetails.FirstConnectionId;
secondConId = registeredInnovation.NewNodeDetails.SecondConnectionId;
}
genome.Genes.Add(new Gene(ConnectionPool.FindById(firstConId), firstConId, 1.0, false));
genome.Genes.Add(new Gene(ConnectionPool.FindById(secondConId), secondConId, geneToSplit.Weight, false));
}
/// <summary>
/// Retrieves the activation function from the given style.
/// </summary>
/// <param name="style">The style corresponding to the function.</param>
/// <returns>The desired activation function.</returns>
public static Func <double, double> GetActivationFunction(ActivationStyle style)
{
switch (style)
{
case ActivationStyle.SigmoidBasic:
return(Sigmoid);
case ActivationStyle.SigmoidNEAT:
return(SigmoidNEAT);
case ActivationStyle.ReLU:
return(ReLU);
case ActivationStyle.None:
return(UnitLine);
default:
throw new Exception("ActivationFunctions.GetActivationFunction style not found.");
break;
}
return(Sigmoid);
}
/// <summary>
/// Basic constructor.
/// </summary>
/// <param name="type">The type of the node.</param>
/// <param name="aFun">The function to be used in activation.</param>
public NodeInformation(NodeType type, ActivationStyle style)
{
Type = type;
Style = style;
}
/// <summary>
/// Constructs a MutationStyle.AddNode innovation.
/// </summary>
/// <param name="conInfo">The original connection being broke.</param>
/// <param name="style">The ActivationStyle of the new node.</param>
public InnovationInformation(ConnectionInformation conInfo, ActivationStyle style)
{
InnovationType = MutationStyle.AddNode;
ConnectionInformation = conInfo;
Style = style;
}
