private static SOMResult TrainSOM(SOMNode[] nodes, ISOMInput[] inputs, SOMRules rules, bool returnEmptyNodes = false)
{
double mapRadius = MathND.GetRadius(MathND.GetAABB(nodes.Select(o => o.Weights)));
SOMNode[] returnNodes = nodes.
Select(o => o.Clone()).
ToArray();
double timeConstant = rules.NumIterations / Math.Log(mapRadius);
int iteration = 0;
int remainingIterations = rules.NumIterations;
while (remainingIterations > 0)
{
foreach (ISOMInput input in UtilityCore.RandomOrder(inputs, Math.Min(remainingIterations, inputs.Length)))
{
// Find closest node
SOMNode closest = GetClosest(returnNodes, input).Item1;
// Find other affected nodes (a node and distance squared)
double searchRadius = mapRadius * rules.InitialRadiusPercent * Math.Exp(-iteration / timeConstant);
Tuple <SOMNode, double>[] neigbors = GetNeighbors(returnNodes, closest, searchRadius);
double learningRate = rules.LearningRate * Math.Exp(-(double)iteration / (double)rules.NumIterations);
// Adjust the matched node (full learning rate)
AdjustNodeWeights(closest, input.Weights, learningRate);
foreach (var node in neigbors)
{
double influence = GetInfluence(rules.AttractionFunction, node.Item2, searchRadius);
// Adjust a neighbor
AdjustNodeWeights(node.Item1, input.Weights, learningRate * influence);
}
iteration++;
}
remainingIterations -= inputs.Length;
}
// See which images go with which nodes
ISOMInput[][] inputsByNode = GetInputsByNode(returnNodes, inputs);
SOMResult retVal = new SOMResult(returnNodes, inputsByNode, true);
if (!returnEmptyNodes)
{
retVal = RemoveZeroNodes(retVal);
}
return(retVal);
}
/// <summary>
/// This version starts with a SOM, then potentially splits the largest node and/or gathers the smallest nodes into a single
/// </summary>
/// <returns></returns>
public static SOMResult Train(ISOMInput[] inputs, SOMRules rules, bool isDisplay2D)
{
SOMResult result = SelfOrganizingMaps.TrainSOM(inputs, rules, isDisplay2D);
if (result.Nodes.Length == 0)
{
return(result);
}
else if (result.Nodes.Length == 1)
{
#region kmeans single node
if (inputs.Length < 20)
{
return(result);
}
return(SelfOrganizingMaps.TrainKMeans(inputs, 5, true));
#endregion
}
var categorized = GetSOM_SplitMerge_Categorize(result);
List <SOMNode> nodes = new List <SOMNode>();
List <ISOMInput[]> newInputs = new List <ISOMInput[]>();
foreach (NodeCombo set in UtilityCore.Iterate(categorized.kmeans, categorized.keep)) // UtilityCore.Iterate gracefully skips nulls
{
nodes.Add(set.Node);
newInputs.Add(set.Inputs);
}
if (categorized.remaining != null)
{
nodes.Add(new SOMNode()
{
Position = MathND.GetCenter(categorized.remaining.Select(o => o.Node.Position)),
Weights = MathND.GetCenter(categorized.remaining.Select(o => o.Node.Weights)),
});
newInputs.Add(categorized.remaining.
SelectMany(o => o.Inputs).
ToArray());
}
return(new SOMResult(nodes.ToArray(), newInputs.ToArray(), false));
}
/// <summary>
/// This overload does an initial training, then recurses on any node that has too wide of a range of values
/// </summary>
/// <remarks>
/// This method is a bit of a failure. Sometimes it works, but other times it just runs without fixing anything
/// </remarks>
/// <param name="maxSpreadPercent">
/// Spread is an input's distance from the center of all inputs. The percent is a node's max distance divided by all node's max distance.
/// .65 to .75 is a good value to use (smaller values will chop up into more nodes)
/// </param>
public static SOMResult TrainSOM(ISOMInput[] inputs, SOMRules rules, double maxSpreadPercent, bool isDisplay2D, bool returnEmptyNodes = false)
{
const int MININPUTSFORSPLIT = 4;
// Get the initial result
SOMResult result = TrainSOM(inputs, rules, isDisplay2D, returnEmptyNodes);
#region Divide large nodes
double totalSpread = GetTotalSpread(inputs.Select(o => o.Weights));
int infiniteLoop = 0;
while (infiniteLoop < 50) // if it exceeds this, just use whatever is there
{
// Split up nodes that have too much variation (image's distance from average)
var reduced = Enumerable.Range(0, result.Nodes.Length).
AsParallel().
Select(o => SplitNode(o, result, MININPUTSFORSPLIT, maxSpreadPercent, totalSpread, rules)).
ToArray();
if (reduced.All(o => !o.Item1))
{
// No changes were needed this pass
break;
}
SOMNode[] reducedNodes = reduced.
SelectMany(o => o.Item2).
ToArray();
// Rebuild result
ISOMInput[][] imagesByNode = SelfOrganizingMaps.GetInputsByNode(reducedNodes, inputs);
result = new SOMResult(reducedNodes, imagesByNode, false);
result = SelfOrganizingMaps.RemoveZeroNodes(result);
infiniteLoop++;
}
#endregion
// Inject positions into the nodes
InjectNodePositions2D(result.Nodes); //TODO: Look at isDisplay2D
result = ArrangeNodes_LikesAttract(result);
return(result);
}
/// <summary>
/// This creates nodes with random weights based on the input's weights. After training, it creates random positions, and arranges
/// the positions so similar sets are near each other
/// </summary>
/// <param name="inputs">These are items turned into vectors. They could be images, db row hashes, whatever</param>
/// <param name="isDisplay2D">This doesn't affect the actual algorithm, just node.Position (true is 2D, false is 3D)</param>
/// <param name="returnEmptyNodes">This shouldn't even be an option. Empty nodes are just artifacts that polute the final result</param>
public static SOMResult TrainSOM(ISOMInput[] inputs, SOMRules rules, bool isDisplay2D, bool returnEmptyNodes = false)
{
VectorND[] nodeWeights = GetRandomNodeWeights(rules.NumNodes, inputs);
SOMNode[] nodes = nodeWeights.
Select(o => new SOMNode()
{
Weights = o
}).
ToArray();
SOMResult retVal = TrainSOM(nodes, inputs, rules, returnEmptyNodes);
// Inject positions into the nodes
InjectNodePositions2D(retVal.Nodes); //TODO: Look at isDisplay2D
retVal = ArrangeNodes_LikesAttract(retVal);
return(retVal);
}
/// <summary>
/// This does a new SOM for one node (sort of like recursing on a node)
/// </summary>
/// <param name="index">The node to break apart</param>
private static Tuple <bool, SOMNode[]> SplitNode(int index, SOMResult result, int minNodeItemsForSplit, double maxSpreadPercent, double totalSpread, SOMRules rules)
{
ISOMInput[] inputs = result.InputsByNode[index];
// Don't split if there aren't enough inputs in the parent
if (inputs.Length < minNodeItemsForSplit)
{
return(Tuple.Create(false, new[] { result.Nodes[index] }));
}
// See how this node's distances from the average compare with the total
double nodeSpread = GetTotalSpread(inputs.Select(o => o.Weights));
double percentSpread = nodeSpread / totalSpread;
if (percentSpread < maxSpreadPercent)
{
return(Tuple.Create(false, new[] { result.Nodes[index] }));
}
// Get random node weights. Don't let any of those weights be closer to other nodes than this node
VectorND[] weights = GetRandomWeights_InsideCell(rules.NumNodes, inputs, result.Nodes, index);
SOMNode[] nodes = Enumerable.Range(0, rules.NumNodes).
Select(o => new SOMNode()
{
Weights = weights[o]
}).
ToArray();
// Split up this node
SOMResult subResult = TrainSOM(nodes, inputs, rules, false);
return(Tuple.Create(true, subResult.Nodes));
}