using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using UnityEngine;
#if UNITY_MATHEMATICS
using Unity.Mathematics;
using static Unity.Mathematics.math;
#endif
namespace NanoBrain {
///
/// A neuron is a basic Nucleus
///
/// A neuron combines the weighted input from other neurons and applies an activation function to it
/// to compute the output value:
/// \code
/// Vector3 combination = NanoBrain::Neuron::Combinator(bias, synapses);
/// Vector3 output = NanoBrain::Neuron::Activator(combination);
/// \endcode
/// The synapses are connections to other neurons.
/// Each connection has a weight which is used to multiply the output of that other neuron
/// before it is used by the combinator.
[Serializable]
public class Neuron : Nucleus {
///
/// Create a new Neuron in a Cluster instance
///
/// The parent cluster in which the new Neuron should be created
/// The name of the new Neuron
public Neuron(Cluster parent, string name) {
this.parent = parent;
this.name = name;
if (this.parent != null) {
this.parent.nuclei ??= new();
this.parent.nuclei.Add(this);
}
}
#region Serialization
///
/// The bias
///
/// The bias which a value which is always added to the combined value of the neuron
/// It does not have a synapse and therefore no weight of source nucleus
//[HideInInspector]
public Vector3 bias = Vector3.zero;
///
/// Indicator whether the bias can be trained
///
public bool trainableBias = false;
#region Synapses
[SerializeField]
private List _synapses = new();
///
/// The synapses of the nucleus
///
public List synapses => _synapses;
///
/// Add a new synapse to this nuclues
///
/// The nucleus from which the signals may originate
/// The weight applied to the input. Default value = 1
/// The created Synapse
/// This will add a new input to this nucleus with the given weight.
public Synapse AddSynapse(Neuron sendingNucleus, float weight = 1, bool trainable = false) {
Synapse synapse = new(sendingNucleus, weight) {
trainable = trainable
};
this.synapses.Add(synapse);
return synapse;
}
///
/// Find a synapse
///
/// The sender of the input to the Synapse
/// The found Synapse or null when the sender has no synapse to this nucleus.
public Synapse GetSynapse(Nucleus sender) {
foreach (Synapse synapse in this.synapses)
if (synapse.neuron == sender)
return synapse;
return null;
}
public Synapse GetSynapse(string senderNeuronName) {
Neuron sender = this.parent.GetNeuron(senderNeuronName);
if (sender == null)
return null;
return this.GetSynapse(sender);
}
public Synapse GetSynapse(Cluster cluster, string senderNeuronName) {
Neuron sender = cluster.GetNeuron(senderNeuronName);
if (sender == null)
return null;
return this.GetSynapse(sender);
}
///
/// Remove a synapse from a Nucleus
///
/// Remote the synapse connecting to this Nucleus
public void RemoveSynapse(Nucleus sendingNucleus) {
this.synapses.RemoveAll(synapse => synapse.neuron == sendingNucleus);
}
#endregion Synapses
///
/// Set the bias, recalculate the output and update all Nuclei receiving from this Nucleus
///
///
public virtual void SetBias(Vector3 inputValue) {
this.bias = inputValue;
this.lastUpdate = Time.time;
this.parent?.UpdateFromNucleus(this);
}
///
/// The type of combinators
///
/// A combinator combines the weighted values of the synapses to a single value
public enum CombinatorType {
/// Add the weighted values together
Sum,
/// Multiply the weighted values
Product,
}
///
/// The type of combinator used for this Neuron
///
[HideInInspector]
public CombinatorType combinator = CombinatorType.Sum;
///
/// The type of
///
public enum ActivationType {
Linear,
Power,
Sqrt,
Reciprocal,
Tanh,
Binary,
Normalized,
Custom
}
///
/// The activation function
///
[SerializeField]
[HideInInspector]
public ActivationType _activator;
///
/// The activation funtion
///
public ActivationType activator {
get { return _activator; }
set {
_activator = value;
//this.curve = GenerateCurve();
}
}
#endregion Serialization
#if UNITY_MATHEMATICS
private readonly List fs = new();
///
/// The output value of the neuron
///
[HideInInspector]
protected float3 _outputValue;
///
/// The output value of the neuron
///
public virtual float3 outputValue {
get {
foreach (var f in fs)
f();
return _outputValue;
}
set {
_outputValue = value;
if (this.isFiring)
WhenFiring?.Invoke();
else
WhenNotFiring?.Invoke();
}
}
public float3 activation => outputValue;
///
/// The magnitude of the neuron output
///
public float outputMagnitude => length(_outputValue);
///
/// The squared magnitude of the neuron output
///
public float outputSqrMagnitude => lengthsq(_outputValue);
#else
///
/// The output value of the neuron
///
protected Vector3 _outputValue;
///
/// The output value of the neuron
///
public virtual Vector3 outputValue {
get { return _outputValue; }
set {
_outputValue = value;
if (this.isFiring)
WhenFiring?.Invoke();
}
}
///
/// The magnitude of the neuron output
///
public float outputMagnitude => _outputValue.magnitude;
///
/// The squared magnitude of the neuron output
///
public float outputSqrMagnitude => _outputValue.sqrMagnitude;
#endif
///
/// True if the neuron have a positive value with magnitude > 0.5
///
public bool isFiring => this.outputMagnitude > 0.5f;
///
/// An action which is called every time the neuron is updated and is firing
///
public Action WhenFiring;
public Action WhenNotFiring;
///
/// When true, the value will not be reset after timeToSleep.
///
public bool persistOutput = false;
///
/// True when the neuron is not persisting and has not be updated for timeToSleep seconds
///
public virtual bool isSleeping => false; //!persistOutput && (Time.time - this.lastUpdate > timeToSleep);
///
/// Check if the neuron is sleeping.
///
/// This will reset the output value if it is sleeping
public void SleepCheck() {
if (this.isSleeping && this.outputSqrMagnitude > 0) {
#if UNITY_MATHEMATICS
this._outputValue = new float3(0, 0, 0);
#else
this._outputValue = new Vector3(0,0,0);
#endif
}
}
///
/// The time at which the last update has been done
///
[HideInInspector]
public float lastUpdate = 0;
///
/// Time in seconds after the last update the neuron can go to sleep
///
public static readonly float timeToSleep = 0.5f;
///
/// When true, Unity will pause exection when this neuron is updated
///
/// Pausing is implemented using [Debug.Break()](https://docs.unity3d.com/ScriptReference/Debug.Break.html)
public bool breakOnUpdate = false;
/// \copydoc NanoBrain::Nucleus::ShallowCloneTo
public override Nucleus ShallowCloneTo(Cluster parent) {
Neuron clone = new(parent, this.name) {
// prefabNucleus = this
};
CloneFields(clone);
return clone;
}
///
/// Copy relevant fields of this neuron to the given neuron
///
///
protected virtual void CloneFields(Neuron clone) {
clone.bias = this.bias;
clone.trainableBias = this.trainableBias;
clone.persistOutput = this.persistOutput;
clone.combinator = this.combinator;
clone.activator = this.activator;
clone.breakOnUpdate = this.breakOnUpdate;
}
public static bool EqualStructure(Neuron neuron1, Neuron neuron2) {
int synapseCount1 = neuron1.synapses.Count;
int synapseCount2 = neuron2.synapses.Count;
if (synapseCount1 != synapseCount2)
return false;
for (int i = 0; i < synapseCount1; i++) {
if (Synapse.EqualStructure(neuron1.synapses[i], neuron2.synapses[i]) == false)
return false;
}
return true;
}
public bool CopyWeightsFrom(Neuron source) {
int thisSynapseCount = this.synapses.Count;
int sourceSynapseCount = source.synapses.Count;
if (thisSynapseCount != sourceSynapseCount)
return false;
for (int i = 0; i < thisSynapseCount; i++) {
Synapse thisSynapse = this.synapses[i];
if (thisSynapse.trainable) {
Synapse sourceSynapse = source.synapses[i];
thisSynapse.weight = sourceSynapse.weight;
}
}
return true;
}
public void ProcessWeightsFrom(Neuron source, Func processor) {
int thisSynapseCount = this.synapses.Count;
int sourceSynapseCount = source.synapses.Count;
if (thisSynapseCount != sourceSynapseCount)
return;
for (int i = 0; i < thisSynapseCount; i++) {
Synapse thisSynapse = this.synapses[i];
if (thisSynapse.trainable) {
Synapse sourceSynapse = source.synapses[i];
thisSynapse.weight = processor(thisSynapse.weight, sourceSynapse.weight);
}
}
}
///
/// Delete the give neuron
///
/// The neuron to delete
public static void Delete(Nucleus nucleus) {
if (nucleus == null)
return;
if (nucleus is Neuron neuron) {
foreach (Synapse synapse in neuron.synapses) {
if (synapse.neuron is Neuron synapse_nucleus) {
if (synapse_nucleus.receivers.Count > 1) {
// there is another nucleus feeding into this input nucleus
synapse_nucleus.receivers.RemoveAll(r => r == nucleus);
}
else {
// No other links, delete it.
Neuron.Delete(synapse_nucleus);
}
}
}
foreach (Nucleus receiver in neuron.receivers) {
if (receiver is not Neuron receiverNeuron)
continue;
if (receiver != null && receiverNeuron.synapses != null)
receiverNeuron.synapses.RemoveAll(s => s.neuron == nucleus);
}
}
else if (nucleus is Cluster cluster) {
// remove all receivers for this cluster
foreach (Nucleus clusterNucleus in cluster.nuclei) {
if (clusterNucleus is Neuron output) {
foreach (Nucleus receiver in output.receivers) {
if (receiver is not Neuron receiverNeuron)
continue;
receiverNeuron.synapses.RemoveAll(s => s.neuron == output);
}
}
}
}
if (nucleus.parent.prefab != null) {
nucleus.parent.nuclei.RemoveAll(n => n == nucleus);
nucleus.parent.RefreshOutputs();
}
}
/// \copydoc NanoBrain::Nucleus::UpdateStateIsolated
public override void UpdateStateIsolated() {
if (breakOnUpdate) {
Debug.Break();
}
this.combination = Combinator(this.bias, this.synapses);
this.outputValue = Activator(this.combination);
this.lastUpdate = Time.time;
}
#region Combinator
#if UNITY_MATHEMATICS
[NonSerialized]
public float3 combination;
///
/// The combinator which combines the bias with the values from all synapses
///
/// The bias of the neuron
/// The synapses of the neuron
///
protected float3 Combinator(float3 bias, List synapses) {
switch (combinator) {
case CombinatorType.Sum:
return CombinatorSum(bias, synapses);
case CombinatorType.Product:
return CombinatorProduct(bias, synapses);
default:
return CombinatorSum(bias, synapses);
}
}
///
/// Sum the bias and synpase outputs together
///
/// The bias of the neuron
/// The synapses of the neuron
///
public static float3 CombinatorSum(float3 bias, List synapses) {
float3 sum = bias;
foreach (Synapse synapse in synapses) {
synapse.neuron.SleepCheck();
sum += synapse.weight * synapse.neuron.outputValue;
}
return sum;
}
///
/// Multiply the synapse outputs together
///
/// The bias of the neuron
/// The synapses of the neuron
/// The result of the multiplication
public static float3 CombinatorProduct(float3 bias, List synapses) {
float3 product = bias;
foreach (Synapse synapse in synapses) {
synapse.neuron.SleepCheck();
product *= synapse.weight * synapse.neuron.outputValue;
}
return product;
}
#else
public Vector3 combinationValue;
///
/// The combinator which combines the bias with the values from all synapses
///
/// The bias of the neuron
/// The synapses of the neuron
///
protected Vector3 Combinator(Vector3 bias, List synapses) {
switch (combinator) {
case CombinatorType.Sum: return CombinatorSum(bias, synapses);
case CombinatorType.Product: return CombinatorProduct(bias, synapses);
default: return CombinatorSum(bias, synapses);
}
}
///
/// Sum the bias and synpase outputs together
///
/// The bias of the neuron
/// The synapses of the neuron
///
public static Vector3 CombinatorSum(Vector3 bias, List synapses) {
Vector3 sum = bias;
foreach (Synapse synapse in synapses) {
synapse.neuron.SleepCheck();
sum += synapse.weight * synapse.neuron.outputValue;
}
return sum;
}
///
/// Multiply the synapse outputs together
///
/// The bias of the neuron
/// The synapses of the neuron
/// The result of the multiplication
public static Vector3 CombinatorProduct(Vector3 bias, List synapses) {
Vector3 product = bias;
foreach (Synapse synapse in synapses) {
synapse.neuron.SleepCheck();
product = Vector3.Scale(product, synapse.weight * synapse.neuron.outputValue);
}
return product;
}
#endif
#endregion Combinator
#region Activator
#if UNITY_MATHEMATICS
///
/// Apply the activation function to the input
///
///
/// The result of applying the activation function
// This does not allocate memory and seems faster than a switch expression
protected float3 Activator(float3 inputValue) {
switch (activator) {
case ActivationType.Linear:
return ActivatorLinear(inputValue);
case ActivationType.Sqrt:
return ActivatorSqrt(inputValue);
case ActivationType.Power:
return ActivatorPower(inputValue);
case ActivationType.Reciprocal:
return ActivatorReciprocal(inputValue);
case ActivationType.Tanh:
return ActivatorTanh(inputValue);
case ActivationType.Binary:
return ActivatorBinary(inputValue);
case ActivationType.Normalized:
return ActivatorNormalized(inputValue);
default:
return ActivatorLinear(inputValue);
}
}
///
/// Linear activation function
///
/// Input value
/// The unchanged value
protected float3 ActivatorLinear(float3 input) {
return input;
}
///
/// Square root activation function
///
/// Input value
/// The square root of the input
protected float3 ActivatorSqrt(float3 input) {
float3 result = normalize(input) * MathF.Sqrt(length(input));
return result;
}
///
/// Power activation function
///
/// Input value
/// The input to the power of 2
protected float3 ActivatorPower(float3 input) {
float3 result = normalize(input) * MathF.Pow(length(input), 2);
return result;
}
///
/// Reciprocal activation function
///
/// Input value
/// 1/input value
protected float3 ActivatorReciprocal(float3 input) {
float magnitude = length(input);
if (magnitude == 0)
return new float3(0, 0, 0);
float3 result = normalize(input) * (1 / magnitude);
return result;
}
///
/// Tanh activation function
///
/// Input value
/// Tanh(input value)
protected float3 ActivatorTanh(float3 input) {
float magnitude = length(input);
float3 result = normalize(input) * MathF.Tanh(magnitude);
return result;
}
///
/// Binary activation function
///
/// Input value
/// An uniform vector with magnitude between 0 and 1
protected float3 ActivatorBinary(float3 input) {
float magnitude = length(input);
float value = Mathf.Clamp01(magnitude);
return float3(value, value, value);
}
///
/// Normalize activation function
///
/// Input value
/// The normalized vector
protected float3 ActivatorNormalized(float3 input) {
if (lengthsq(input) == 0)
return input;
float3 result = normalize(input);
return result;
}
#else
///
/// Apply the activation function to the input
///
///
/// The result of applying the activation function
// This does not allocate memory and seems faster than a switch expression
protected Vector3 Activator(Vector3 inputValue) {
switch (activator) {
case ActivationType.Linear: return ActivatorLinear(inputValue);
case ActivationType.Sqrt: return ActivatorSqrt(inputValue);
case ActivationType.Power: return ActivatorPower(inputValue);
case ActivationType.Reciprocal: return ActivatorReciprocal(inputValue);
// case ActivationType.Tanh: return ActivatorTanh(inputValue);
// case ActivationType.Binary: return ActivatorBinary(inputValue);
// case ActivationType.Normalized: return ActivatorNormalized(inputValue);
default: return ActivatorLinear(inputValue);
}
}
///
/// Linear activation function
///
/// Input value
/// The unchanged value
protected Vector3 ActivatorLinear(Vector3 input) {
return input;
}
///
/// Square root activation function
///
/// Input value
/// The square root of the input
protected Vector3 ActivatorSqrt(Vector3 input) {
Vector3 result = input.normalized * System.MathF.Sqrt(input.magnitude);
return result;
}
///
/// Power activation function
///
/// Input value
/// The input to the power of 2
protected Vector3 ActivatorPower(Vector3 input) {
Vector3 result = input.normalized * System.MathF.Pow(input.magnitude, 2);
return result;
}
///
/// Reciprocal activation function
///
/// Input value
/// 1/input value
protected Vector3 ActivatorReciprocal(Vector3 input) {
float magnitude = input.magnitude;
if (magnitude == 0)
return new Vector3(0, 0, 0);
Vector3 result = input.normalized * (1 / magnitude);
return result;
}
#endif
#endregion Activator
#region Receivers
///
/// The nuclei which have a synapse to this neuron
///
[SerializeReference]
[HideInInspector]
private List _receivers = new();
///
/// The nuclei which have a synapse to this neuron
///
public virtual List receivers {
get { return _receivers; }
set { _receivers = value; }
}
///
/// Add a new receiver to this neuron
///
/// The receiver to add
/// The weight to use for the synapse to his neuron
public virtual void AddReceiver(Nucleus receiverToAdd, float weight = 1, bool trainable = false) {
if (receiverToAdd is not Neuron receiverNeuron)
return;
this._receivers.Add(receiverNeuron);
receiverNeuron.AddSynapse(this, weight, trainable);
}
///
/// Remove a receiver to this neuron
///
/// The receiver to remove
public virtual void RemoveReceiver(Nucleus receiverToRemove) {
if (receiverToRemove is not Neuron receiverNeuron)
return;
this._receivers.RemoveAll(receiver => receiver == receiverNeuron);
receiverNeuron.synapses.RemoveAll(synapse => synapse.neuron == this);
// Nucleus prefabReceiver = receiverToRemove.prefabNucleus;
// if (this.prefabNucleus is Neuron prefabNeuron && prefabReceiver != null) {
// prefabNeuron.receivers.RemoveAll(receiver => receiver == prefabReceiver);
// prefabReceiver.synapses.RemoveAll(synapse => synapse.neuron == prefabNeuron);
// }
}
#endregion Receivers
#region Back propagation
public void BackPropagation1D(float derivative, float learningRate) {
foreach (Synapse synapse in this.synapses)
synapse.BackPropagation(this, derivative, learningRate);
// Bias
if (this.trainableBias) {
// This does not work well, because the derivative/error does not have a 3D direction
// float3 biasDerivative = derivative; // dSSR/dActivator
// switch (activator) { // dActivator/dBias
// case ActivationType.Linear:
// //deltaBias *= 1;
// break;
// default:
// break;
// }
// Vector3 deltaBias = biasDerivative * learningRate;
// this.bias -= deltaBias;
}
}
public void BackPropagation3D(Vector3 derivative, float learningRate) {
float derivativeMagnitude = derivative.magnitude;
if (derivativeMagnitude < 1e-03f)
// Small changes are not processed
// We are probably very close to the desired output
return;
foreach (Synapse synapse in this.synapses)
synapse.BackPropagation3D(this, derivative, learningRate);
// As the weight cannot change the direction of the derivative
// we can use the simpler, 1D backpropagation here
// But we still need to determine the sign of the derivative
// if (Synapse.AreOpposed(derivative, synapse.neuron.activation))
// synapse.BackPropagation(this, -derivativeMagnitude, learningRate);
// else
// synapse.BackPropagation(this, derivativeMagnitude, learningRate);
// Bias
if (this.trainableBias) {
switch (this.activator) { // dActivator/dBias
case ActivationType.Linear:
derivative *= 1;
break;
default:
break;
}
this.bias += derivative * learningRate;
Debug.Log($"bias {derivative} {this.bias}");
}
}
#endregion Back propagation
private CancellationTokenSource _cts;
///
/// Process an external stimulus
///
/// The value of the stimulus
public virtual void ProcessStimulus(Vector3 inputValue, float autoResetDelay = 0) {
this.lastUpdate = Time.time;
this.bias = inputValue;
this.parent?.UpdateFromNucleus(this);
if (autoResetDelay > 0) {
_cts?.Cancel();
_cts?.Dispose();
_cts = new CancellationTokenSource();
_ = CallResetAfterDelayAsync(_cts.Token, autoResetDelay);
}
}
private async Task CallResetAfterDelayAsync(CancellationToken token, float autoResetDelay) {
try {
await Task.Delay(TimeSpan.FromSeconds(autoResetDelay), token);
if (!token.IsCancellationRequested)
ResetStimulus();
}
catch (TaskCanceledException) {
// Expected when Stimulus is called again; do nothing
}
}
protected void ResetStimulus() {
//Debug.Log("reset stimulus");
this.bias = Vector3.zero;
this.parent?.UpdateFromNucleus(this);
}
}
[Serializable]
public class NeuronData {
public string name;
public Nucleus.Type type;
public Vector3 bias = Vector3.zero;
public Neuron.CombinatorType combinatorType;
public List synapses = new();
public Neuron.ActivationType activationType;
public NeuronData(Neuron neuron) {
if (neuron is MemoryCell)
this.type = Nucleus.Type.MemoryCell;
else
this.type = Nucleus.Type.Neuron;
this.name = neuron.name;
this.bias = neuron.bias;
this.combinatorType = neuron.combinator;
this.activationType = neuron.activator;
foreach (Synapse synapse in neuron.synapses) {
SynapseData synapseData = new(synapse);
this.synapses.Add(synapseData);
}
}
}
}